text: In medicine, subclavian steal syndrome (SSS), also called subclavian steal phenomenon or subclavian steal steno-occlusive disease, is a constellation of signs and symptoms that arise from retrograde (reversed) blood flow in the vertebral artery or the internal thoracic artery, due to a proximal stenosis (narrowing) and/or occlusion of the subclavian artery. The arm may be supplied by blood flowing in a retrograde direction down the vertebral artery at the expense of the vertebrobasilar circulation. This is called the subclavian steal. It is more severe than typical vertebrobasilar insufficiency.

text: In medicine, subclavian steal syndrome (SSS), also called subclavian steal phenomenon or subclavian steal steno-occlusive disease, is a constellation of

entity_name: Medical sign

text: signs

text: and

entity_name: Symptom

text: symptom

text: s that arise from retrograde (reversed)

entity_name: Blood flow

text: blood flow

text: in the

entity_name: Vertebral artery

text: vertebral artery

text: or the

entity_name: Internal thoracic artery

text: internal thoracic artery

text: , due to a

entity_name: Anatomical terms of location

entity_section: Proximal and distal

text: proximal

entity_name: Stenosis

text: stenosis

text: (narrowing) and/or occlusion of the

entity_name: Subclavian artery

text: subclavian artery

text: . The arm may be supplied by blood flowing in a retrograde direction down the vertebral artery at the expense of the vertebrobasilar circulation. This is called the subclavian steal. It is more severe than typical

entity_name: Vertebrobasilar insufficiency

text: vertebrobasilar insufficiency

text: The Introduction closes with Arthur – still refusing to claim that the play is real – facilitating its publication anyway. Arthur meditates on the artificiality of endings, and points out that the reader's reaction to The Tragedy of Arthur rests on how they interpret the story told in the Introduction. He sums up the project by claiming that those "who know [him] personally know to a fine degree how much of all this is true, how much an apology (and how sincere), how much a boast or a con job. To the rest of you, it's a muddle or it's a thing of beauty. And if it pleased you, and you found in its candor and lies and sobbing cross-dressed confessions some hours' entertainment, then well and good."

text: Stern's research is on the processes that establish cell diversity and pattern at early stages of development in vertebrate embryos.

text: The cause of platyspondyly in fibrochondrogenesis can be attributed in part to odd malformations and structural flaws found in the vertebral bodies of the spinal column in affected infants.

text: The cause of platyspondyly in fibrochondrogenesis can be attributed in part to odd malformations and structural flaws found in the

entity_name: Vertebra

text: vertebral bodies

text: of the spinal column in affected infants.

text: The upper jaw, or maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible (lower jaw), which is also a fusion of two halves at the mandibular symphysis. In bony fish, the maxilla is called the "upper maxilla," with the mandible being the "lower maxilla". The alveolar process of the maxilla holds the upper teeth, and is referred to as the maxillary arch. In most vertebrates, the foremost part of the upper jaw, to which the incisors are attached in mammals consists of a separate pair of bones, the premaxillae. In bony fish, both maxilla and premaxilla are relatively plate-like bones, forming only the sides of the upper jaw, and part of the face, with the premaxilla also forming the lower boundary of the nostrils. Cartilaginous fish, such as sharks and rays also lack a true maxilla. Their upper jaw is instead formed from a cartilagenous bar that is not homologous with the bone found in other vertebrates.

text: The upper jaw, or

entity_name: Maxilla

text: maxilla

text: is a fusion of two bones along the

entity_name: Palate

text: palatal

text: fissure that form the upper

entity_name: Jaw

text: jaw

text: . This is similar to the mandible (lower jaw), which is also a fusion of two halves at the mandibular symphysis. In bony fish, the maxilla is called the "upper maxilla," with the mandible being the "lower maxilla". The

entity_name: Alveolar process

text: alveolar process

text: of the maxilla holds the upper teeth, and is referred to as the maxillary arch. In most vertebrates, the foremost part of the upper jaw, to which the

entity_name: Incisor

text: incisor

text: s are attached in mammals consists of a separate pair of bones, the

entity_name: Premaxilla

text: premaxilla

text: e. In

entity_name: Osteichthyes

text: bony fish

text: , both maxilla and premaxilla are relatively plate-like bones, forming only the sides of the upper jaw, and part of the face, with the premaxilla also forming the lower boundary of the

entity_name: Nostril

text: nostril

text: s.

entity_name: Chondrichthyes

text: Cartilaginous fish

text: , such as sharks and rays also lack a true maxilla. Their upper jaw is instead formed from a

entity_name: Cartilage

text: cartilage

text: nous bar that is not

entity_name: Homology (biology)

text: homologous

text: with the bone found in other vertebrates.

text: In the upper part of the vertebral column, spinal nerves exit directly from the spinal cord, whereas in the lower part of the vertebral column nerves pass further down the column before exiting. The terminal portion of the spinal cord is called the conus medullaris. The pia mater continues as an extension called the filum terminale, which anchors the spinal cord to the coccyx. The cauda equina ("horse's tail") is the name for the collection of nerves in the vertebral column that continue to travel through the vertebral column below the conus medullaris. The cauda equina forms because the spinal cord stops growing in length at about age four, even though the vertebral column continues to lengthen until adulthood. This results in sacral spinal nerves originating in the upper lumbar region.

text: In the upper part of the vertebral column, spinal nerves exit directly from the spinal cord, whereas in the lower part of the vertebral column nerves pass further down the column before exiting. The terminal portion of the spinal cord is called the

entity_name: Conus medullaris

text: conus medullaris

text: . The

entity_name: Pia mater

text: pia mater

text: continues as an extension called the

entity_name: Filum terminale

text: filum terminale

text: , which anchors the spinal cord to the

entity_name: Coccyx

text: coccyx

text: . The

entity_name: Cauda equina

text: cauda equina

text: ("horse's tail") is the name for the collection of nerves in the vertebral column that continue to travel through the vertebral column below the

text: conus medullaris

text: . The cauda equina forms because the spinal cord stops growing in length at about age four, even though the vertebral column continues to lengthen until adulthood. This results in sacral spinal nerves originating in the upper lumbar region.

method: UNH-tfidf-stem

method: UNH-tfidf-ptsim

method: UNH-tfidf-lem

text: In conclusion, both DeMar and Dilkes clarify that the osteoderm growth covers the first sections of the anterior vertebral column and grows posteriorly with fusion of the next posterior vertebral sections. This means that reduction of flexibility starts anteriorly and proceeds posteriorly, thus it is likely that "as juveniles both Cacops and Dissorophus had greater vertebral flexibility" as mentioned by Dilkes.

text: Sinornithosaurus was discovered by Xu Xing, Wang Xiaolin and Wu Xiaochun of the Institute of Vertebrate Paleontology and Paleoanthropology of Beijing. An almost-complete fossil with feather impressions, was recovered from Liaoning Province, China, in the Yixian Formation; the same incredibly rich location where four dinosaurs with feathers were discovered previously, Protarchaeopteryx, Sinosauropteryx, Caudipteryx, and Beipiaosaurus. The holotype specimen is IVPP V12811, in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China.

text: Sinornithosaurus was discovered by Xu Xing, Wang Xiaolin and Wu Xiaochun of the Institute of Vertebrate Paleontology and Paleoanthropology of

entity_name: Beijing

text: Beijing

text: . An almost-complete

entity_name: Fossil

text: fossil

text: with feather impressions, was recovered from

entity_name: Liaoning

text: Liaoning Province

text: , China, in the

entity_name: Yixian Formation

text: Yixian Formation

text: ; the same incredibly rich location where four dinosaurs with feathers were discovered previously,

entity_name: Protarchaeopteryx

text: Protarchaeopteryx

entity_name: Sinosauropteryx

text: Sinosauropteryx

entity_name: Caudipteryx

text: Caudipteryx

text: , and

entity_name: Beipiaosaurus

text: Beipiaosaurus

text: . The holotype specimen is IVPP V12811, in the collection of the

entity_name: Institute of Vertebrate Paleontology and Paleoanthropology

text: Institute of Vertebrate Paleontology and Paleoanthropology

text: in

text: Beijing

entity_name: China

text: China

text: The upper esophagus lies at the back of the mediastinum behind the trachea, adjoining along the tracheoesophageal stripe, and in front of the erector spinae muscles and the vertebral column. The lower esophagus lies behind the heart and curves in front of the thoracic aorta. From the bifurcation of the trachea downwards, the esophagus passes behind the right pulmonary artery, left main bronchus, and left atrium. At this point it passes through the diaphragm.

text: The upper esophagus lies at the back of the mediastinum behind the

entity_name: Trachea

text: trachea

text: , adjoining along the

entity_name: Tracheoesophageal stripe

text: tracheoesophageal stripe

text: , and in front of the

entity_name: Erector spinae muscles

text: erector spinae muscle

text: s and the

entity_name: Vertebral column

text: vertebral column

text: . The lower esophagus lies behind the

entity_name: Heart

text: heart

text: and curves in front of the

entity_name: Thoracic aorta

text: thoracic aorta

text: . From the

entity_name: Carina of trachea

text: bifurcation of the trachea

text: downwards, the esophagus passes behind the right

entity_name: Pulmonary artery

text: pulmonary artery

entity_name: Bronchus

text: left main bronchus

text: , and

entity_name: Atrium (heart)

text: left atrium

text: . At this point it passes through the diaphragm.

text: At birth, a large part of the scapula is osseous, but the glenoid cavity, the coracoid process, the acromion, the vertebral border and the inferior angle are cartilaginous. From the 15th to the 18th month after birth, ossification takes place in the middle of the coracoid process, which as a rule becomes joined with the rest of the bone about the 15th year.

text: At birth, a large part of the scapula is osseous, but the

entity_name: Glenoid cavity

text: glenoid cavity

text: , the coracoid process, the acromion, the vertebral border and the

entity_name: Scapula

text: inferior angle

text: are

text: cartilaginous

text: . From the 15th to the 18th month after birth, ossification takes place in the middle of the coracoid process, which as a rule becomes joined with the rest of the

entity_name: Bone

text: bone

text: about the 15th year.

text: Although bone may appear superficially as a static tissue, it is actually very dynamic, undergoing constant remodeling throughout the life of the vertebrate organism.  This occurs with the synchronized action of osteoclasts and osteoblasts, cells that resorb and deposit bone, respectively.

text: Although bone may appear superficially as a static tissue, it is actually very dynamic, undergoing constant

entity_name: Bone remodeling

text: remodeling

text: throughout the life of the vertebrate organism.  This occurs with the synchronized action of

entity_name: Osteoclast

text: osteoclast

text: s and

entity_name: Osteoblast

text: osteoblast

text: s, cells that resorb and deposit bone, respectively.

method: dangnt-nlp

text: Reproduction is by budding, where the cell undergoes longitudinal fission and only one daughter keeps the stalk. The free daughter becomes a telotroch, which swims until it finds suitable substrate to fix and develop its own stalk. They reproduce by fission, which is also known as cell division. They are also capable of reproducing by conjugation, a form of sexual reproduction where two individuals attach at the oral groove and exchange DNA.

text: Reproduction is by

entity_name: Budding

text: budding

text: , where the cell undergoes longitudinal fission and only one daughter keeps the stalk. The free daughter becomes a

entity_name: Telotroch

text: telotroch

text: , which swims until it finds suitable substrate to fix and develop its own stalk. They reproduce by fission, which is also known as cell division. They are also capable of reproducing by conjugation, a form of sexual reproduction where two individuals attach at the oral groove and exchange

entity_name: DNA

text: DNA

text: The lineage that produced land vertebrates evolved later but very rapidly between  and ; recent discoveries have overturned earlier ideas about the history and driving forces behind their evolution. Land plants were so successful that they caused an ecological crisis in the Late Devonian, until the evolution and spread of fungi that could digest dead wood.

text: The lineage that produced land vertebrates evolved later but very rapidly between  and ; recent discoveries have overturned earlier ideas about the history and driving forces behind their evolution. Land plants were so successful that they caused an

entity_name: Ecological crisis

text: ecological crisis

text: in the Late

entity_name: Devonian

text: Devonian

text: , until the evolution and spread of fungi that could digest dead wood.

text: Functional coupling takes the idea that organisms are integrated networks of functional interactions (for example, the vertebral column of vertebrates is involved in the muscle, nerve, and vascular systems as well as providing support and flexibility) and therefore cannot be radically altered without causing severe functional disruption. This may be viewed as one type of trade-off. As Rupert Riedl pointed out, this degree of functional constraint — or burden — generally varies according to position in the organism. Structures literally in the centre of the organism — such as the vertebral column — are often more burdened than those at the periphery, such as hair or toes.

text: Functional coupling takes the idea that organisms are integrated networks of functional interactions (for example, the vertebral column of

entity_name: Vertebrate

text: vertebrate

text: s is involved in the muscle, nerve, and vascular systems as well as providing support and flexibility) and therefore cannot be radically altered without causing severe functional disruption. This may be viewed as one type of

entity_name: Trade-off

text: trade-off

text: . As

entity_name: Rupert Riedl

text: Rupert Riedl

text: pointed out, this degree of functional constraint — or burden — generally varies according to position in the organism. Structures literally in the centre of the organism — such as the vertebral column — are often more burdened than those at the periphery, such as hair or toes.

text: Research from the late 1800s to the 1980s suggests a trend of intentional stockings of non-indigenous fishes into ponds, lakes and rivers in the United States. At that time, little was known about environmental impacts, or long-term effects of new species establishment and spread as a result of "fish rescue and transfer" efforts, or the importance of nongame fishes to the ecological balance of aquatic ecosystems.  Introductions of bowfin to areas they were considered a non-indigenous species included various lakes, rivers and drainages in Connecticut, Illinois, Iowa, Kansas, Kentucky Maryland, Massachusetts, Missouri, New Jersey, New York, North Carolina, Pennsylvania, Virginia, West Virginia, and Wisconsin.  Many of the introductions were intentional stockings by various resource management; however, there is no way to positively determine distribution resulting from flood transfers, or other inadvertent migrations.  Bowfin are typically piscivorous, but as an introduced species are capable of being voracious predators that pose a threat to native fishes and their prey.

text: A diverse vertebrate fauna has been described from the Moenkopi Formation, mainly from the Wupatki Member and Holbrook Member of northern Arizona. Described basal vertebrates include freshwater hybodont sharks, coelacanths, and lungfish. Temnospondyl amphibians are a common component of the fauna. Temnospondyli include Eocyclotosaurus, Quasicyclotosaurus, Wellesaurus, Vigilius, and Cosgriffius. The rhynchosaur Ammorhynchus is known, but rare. Anisodontosaurus is an enigmatic reptile only known from a few tooth-bearing jaws. The poposauroid archosaur Arizonasaurus is known from one relatively complete skeleton and a significant amount of other isolated material. Footprints and several fragmentary body fossils are known from dicynodonts. The footprints of Cheirotherium and Rhynchosauroides are common in the Wupatki Member.

text: A diverse vertebrate fauna has been described from the Moenkopi Formation, mainly from the

text: Wupatki Member

text: and

text: Holbrook Member

text: of northern Arizona. Described

entity_name: Basal (phylogenetics)

text: basal

text: vertebrates include freshwater

entity_name: Hybodontidae

text: hybodont

entity_name: Shark

text: shark

text: s,

entity_name: Coelacanth

text: coelacanth

text: s, and

entity_name: Lungfish

text: lungfish

text: . Temnospondyl

entity_name: Amphibian

text: amphibian

text: s are a common component of the fauna.

text: Temnospondyli

text: include

text: Eocyclotosaurus

text: Quasicyclotosaurus

text: Wellesaurus

text: Vigilius

text: , and

text: Cosgriffius

text: . The

text: rhynchosaur

text: Ammorhynchus

text: is known, but rare.

text: Anisodontosaurus

text: is an enigmatic reptile only known from a few tooth-bearing jaws. The poposauroid archosaur

text: Arizonasaurus

text: is known from one relatively complete skeleton and a significant amount of other isolated material. Footprints and several fragmentary body fossils are known from

text: dicynodont

text: s. The footprints of

text: Cheirotherium

text: and

text: Rhynchosauroides

text: are common in the

text: Wupatki Member

text: Elastic mechanisms are very important in the movement of vertebrate animals. The muscles that control vertebrate locomotion are affiliated with tissues that are springy, such as tendons, which lie within the muscles and connective tissue. A spring can be a mechanism for different actions involved in hopping, running, walking, and serve in other diverse functions such as  metabolic energy conservation, attenuation of muscle power production, and amplification of muscle power production.

text: Elastic

text: mechanisms are very important in the movement of

text: vertebrate

text: animals. The

text: muscles

text: that control vertebrate locomotion are affiliated with tissues that are springy, such as

text: tendons

text: , which lie within the muscles and connective tissue. A

text: spring

text: can be a mechanism for different actions involved in hopping, running, walking, and serve in other diverse functions such as  metabolic energy conservation, attenuation of muscle power production, and amplification of muscle power production.

text: Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a backbone or spine), derived from the notochord. This includes all animals apart from the subphylum Vertebrata. Familiar examples of invertebrates include insects; crabs, lobsters and their kin; snails, clams, octopuses and their kin; starfish, sea-urchins and their kin; and worms.The majority of animal species are invertebrates; one estimate puts the figure at 97%.  Many invertebrate taxa have a greater number and variety of species than the entire subphylum of Vertebrata.

text: Invertebrates are

text: animal

text: s that neither possess nor develop a

text: vertebral column

text: (commonly known as a backbone or spine), derived from the

text: notochord

text: . This includes all

text: animal

text: s apart from the

text: subphylum

text: Vertebrata

text: . Familiar examples of invertebrates include

text: insect

text: s;

text: crabs, lobsters and their kin

text: snails, clams, octopuses and their kin

text: starfish, sea-urchins and their kin

text: ; and

text: worm

text: s.The majority of animal species are invertebrates; one estimate puts the figure at 97%.  Many invertebrate

text: taxa

text: have a greater number and variety of species than the entire subphylum of Vertebrata.

text: Rhabdomeric opsins (or r-opsins) are also known as Gq-opsins, because they couple to a Gq-protein. R-opsins are used by molluscs and arthropods.  Arthropods appear to attain colour vision in a similar fashion to the vertebrates, by using three (or more) distinct groups of opsins, distinct both in terms of phylogeny and spectral sensitivity.  The r-opsin melanopsin is also expressed in vertebrates, where it regulates circadian rhythms and mediates the pupillary reflex.

text: Rhabdomeric opsins (or r-opsins) are also known as Gq-opsins, because they couple to a Gq-protein. R-opsins are used by molluscs and arthropods.  Arthropods appear to attain colour vision in a similar fashion to the vertebrates, by using three (or more) distinct groups of opsins, distinct both in terms of phylogeny and spectral sensitivity.  The r-opsin melanopsin is also expressed in vertebrates, where it regulates

text: circadian rhythm

text: s and mediates the pupillary reflex.

text: In Canada, forests cover about 10% of the land area and yet harbor 70% of the country’s bird and terrestrial mammal species. Natural fire regimes are important in maintaining a diverse assemblage of vertebrate species in up to twelve different forest types in British Columbia. Different species have adapted to exploit the different stages of succession, regrowth and habitat change that occurs following an episode of burning, such as downed trees and debris. The characteristics of the initial fire, such as its size and intensity, cause the habitat to evolve differentially afterwards and influence how vertebrate species are able to use the burned areas.

text: In

text: Canada

text: , forests cover about 10% of the land area and yet harbor 70% of the country’s bird and terrestrial mammal species. Natural fire regimes are important in maintaining a diverse assemblage of

text: vertebrate

text: species in up to twelve different forest types in

text: British Columbia

text: . Different species have adapted to exploit the different stages of succession, regrowth and habitat change that occurs following an episode of burning, such as downed trees and debris. The characteristics of the initial fire, such as its size and intensity, cause the habitat to evolve differentially afterwards and influence how vertebrate species are able to use the burned areas.

text: Bibliography on Alternatives to the Use of Live Vertebrates in Biomedical Research and Testing, or Altbib, is a bibliography available online to assist in identifying methods and procedures helpful in supporting the development, testing, application, and validation of alternatives to the use of vertebrates in biomedical research and toxicology testing. The bibliography is produced from MEDLARS database searches analyzed by experts from the Toxicology and Environmental Health Information Program (TEHIP) of the Specialized Information Services Division (SIS) of the National Library of Medicine.

text: Bibliography on Alternatives to the Use of Live Vertebrates in Biomedical Research and Testing, or Altbib, is a

text: bibliography

text: available online to assist in identifying methods and procedures helpful in supporting the development, testing, application, and validation of alternatives to the use of

text: vertebrate

text: s in

text: biomedical research

text: and

text: toxicology

text: testing. The bibliography is produced from

text: MEDLARS

text: database

text: searches analyzed by experts from the Toxicology and

text: Environmental Health

text: Information Program (

text: TEHIP

text: ) of the Specialized Information Services Division (SIS) of the

entity_name: United States National Library of Medicine

text: National Library of Medicine

text: Cartilage is composed of cells embedded in an extracellular matrix of collagen fibers and proteoglycans. It contains no blood vessels therefore its cells are dependent upon diffusion for the supply of oxygen and nutrients. Its intrinsic healing capacity is low. Injury to cartilage can lead to pain and stiffness and is the precursor to the development of osteoarthritis (degenerative joint arthritis).

text: Cartilage is composed of cells embedded in an

text: extracellular matrix

text: of

text: collagen fibers

text: and

text: proteoglycans

text: . It contains no blood vessels therefore its cells are dependent upon

text: diffusion

text: for the supply of oxygen and nutrients. Its intrinsic healing capacity is low. Injury to cartilage can lead to pain and stiffness and is the precursor to the development of

text: osteoarthritis

text: (degenerative joint arthritis).

text: Parthenogenesis in sharks has been confirmed in the bonnethead and zebra shark. Other, usually sexual species, may occasionally reproduce parthenogenetically, and the hammerhead and blacktip sharks are recent additions to the known list of facultative parthenogenetic vertebrates.

text: Parthenogenesis in sharks has been confirmed in the

text: bonnethead

text: and

text: zebra shark

text: . Other, usually sexual species, may occasionally reproduce parthenogenetically, and the

text: hammerhead

text: and

text: blacktip shark

text: s are recent additions to the known list of facultative parthenogenetic vertebrates.

text: Excavations were resumed during spring of 2011, from May 15 to July 1, with the support and permission of SWSD and the State of Colorado. By the end of July, the total number of bones recovered was around 4,826, from at least 26 different Ice Age vertebrates. Approximately 3,000 of them are believed to come from mastodons of both sexes and of varying ages, from infants to full adults. Other new animals recovered included an Ice Age camel (Camelops), a horse, and various smaller vertebrates.

text: Excavations were resumed during spring of 2011, from May 15 to July 1, with the support and permission of SWSD and the State of Colorado. By the end of July, the total number of bones recovered was around 4,826, from at least 26 different Ice Age vertebrates. Approximately 3,000 of them are believed to come from

text: mastodon

text: s of both sexes and of varying ages, from infants to full adults. Other new animals recovered included an Ice Age camel (

text: Camelops

text: ), a

text: horse

text: , and various smaller vertebrates.

text: All vertebrates have a similar basic body plan and at some point in their lives, mostly in the embryonic stage, share the major chordate characteristics; a stiffening rod, the notochord; a dorsal hollow tube of nervous material, the neural tube; pharyngeal arches; and a tail posterior to the anus. The spinal cord is protected by the vertebral column and is above the notochord and the gastrointestinal tract is below it. Nervous tissue is derived from the ectoderm, connective tissues are derived from mesoderm, and gut is derived from the endoderm. At the posterior end is a tail which continues the spinal cord and vertebrae but not the gut. The mouth is found at the anterior end of the animal, and the anus at the base of the tail. The defining characteristic of a vertebrate is the vertebral column, formed in the development of the segmented series of vertebrae. In most vertebrates the notochord becomes the nucleus pulposus of the intervertebral discs. However, a few vertebrates, such as the sturgeon and the coelacanth retain the notochord into adulthood. Jawed vertebrates are typified by paired appendages, fins or legs, which may be secondarily lost. The limbs of vertebrates are considered to be homologous because the same underlying skeletal structure was inherited from their last common ancestor. This is one of the arguments put forward by Charles Darwin to support his theory of evolution.

text: All

text: vertebrate

text: s have a similar basic

text: body plan

text: and at some point in their lives, mostly in the

text: embryonic

text: stage, share the major

text: chordate

text: characteristics; a stiffening rod, the

text: notochord

text: ; a dorsal hollow tube of nervous material, the

text: neural tube

text: pharyngeal arch

text: es; and a tail posterior to the anus. The

text: spinal cord

text: is protected by the

text: vertebral column

text: and is above the notochord and the

text: gastrointestinal tract

text: is below it. Nervous tissue is derived from the

text: ectoderm

text: , connective tissues are derived from

text: mesoderm

text: , and gut is derived from the

text: endoderm

text: . At the posterior end is a

text: tail

text: which continues the spinal cord and vertebrae but not the gut. The mouth is found at the anterior end of the animal, and the

text: anus

text: at the base of the tail. The defining characteristic of a vertebrate is the

text: vertebral column

text: , formed in the development of the segmented series of

text: vertebra

text: e. In most vertebrates the notochord becomes the

text: nucleus pulposus

text: of the

text: intervertebral disc

text: s. However, a few vertebrates, such as the

text: sturgeon

text: and the

text: coelacanth

text: retain the notochord into adulthood.

text: Jawed vertebrates

text: are typified by paired appendages, fins or legs, which may be secondarily lost. The limbs of vertebrates are considered to be

text: homologous

text: because the same underlying skeletal structure was inherited from their last common ancestor. This is one of the arguments put forward by

text: Charles Darwin

text: to support his theory of

text: evolution

text: Nonetheless, the general features of the olfactory system are highly conserved among vertebrates, and, similarly to other sensory systems, olfaction has undergone fairly modest changes throughout the evolution of vertebrates. Phylogenetic analyses reveal that at least three distinct olfactory subsystems are broadly consistent in vertebrates, and a fourth accessory system (vomeronasal) solely arose in tetrapods.

text: Nonetheless, the general features of the olfactory system are highly conserved among vertebrates, and, similarly to other sensory systems, olfaction has undergone fairly modest changes throughout the evolution of vertebrates.

text: Phylogenetic

text: analyses reveal that at least three distinct olfactory subsystems are broadly consistent in vertebrates, and a fourth accessory system (

text: vomeronasal

text: ) solely arose in

text: tetrapod

text: s.

text: Rhabdodon priscus is known from a specimen from the Marnes Rouges Inférieures Formation. The material of Rhabdodon priscus includes a dentary and many other postcranial remains. More specifically, it is known from the Bellevue layer, which has produced many vertebrate fossils. Even though it produced many vertebrates, the formation only has a scarce record of plants and invertebrates. The non-dinosaurian vertebrates consist of Lepisosteus, an indeterminate turtle, and a crocodile. Dinosaurian fauna from the Marnes Rouges Inférieures Formation include Ampelosaurus, an animal classified as Dromaeosauridae indet., and an indeterminate ankylosaur. The bird Gargantuavis philoinos, and dinosaur eggs have also been recovered.

text: Rhabdodon priscus is known from a specimen from the

text: Marnes Rouges Inférieures Formation

text: . The material of Rhabdodon priscus includes a dentary and many other postcranial remains. More specifically, it is known from the Bellevue layer, which has produced many vertebrate fossils. Even though it produced many vertebrates, the formation only has a scarce record of plants and invertebrates. The non-dinosaurian vertebrates consist of

text: Lepisosteus

text: , an indeterminate turtle, and a crocodile. Dinosaurian fauna from the Marnes Rouges Inférieures Formation include

text: Ampelosaurus

text: , an animal classified as Dromaeosauridae indet., and an indeterminate ankylosaur. The bird

text: Gargantuavis philoinos

text: , and dinosaur eggs have also been recovered.

text: Wobbler disease is a catchall term referring to several possible malformations of the cervical vertebrae that cause an unsteady (wobbly) gait and weakness in dogs and horses. A number of different conditions of the cervical (neck) spinal column cause similar clinical signs. These conditions may include malformation of the vertebrae, intervertebral disc protrusion, and disease of the interspinal ligaments, ligamenta flava, and articular facets of the vertebrae. Wobbler disease is also known as cervical vertebral instability, cervical spondylomyelopathy (CSM), and cervical vertebral malformation (CVM). In dogs, the disease is most common in large breeds, especially Great Danes and Doberman Pinschers. In horses, it is not linked to a particular breed, though it is most often seen in tall, race-bred horses of Thoroughbred or Standardbred ancestry. It is most likely inherited to at least some extent in dogs and horses.

text: Wobbler disease is a catchall term referring to several possible malformations of the

text: cervical vertebrae

text: that cause an unsteady (wobbly) gait and weakness in

text: dog

text: s and

text: horse

text: s. A number of different conditions of the cervical (neck) spinal column cause similar clinical signs. These conditions may include malformation of the vertebrae,

text: intervertebral disc

text: protrusion, and disease of the

text: interspinal ligament

text: s,

text: ligamenta flava

text: , and

text: articular facet

text: s of the vertebrae. Wobbler disease is also known as cervical vertebral instability, cervical spondylomyelopathy (CSM), and cervical vertebral malformation (CVM). In dogs, the disease is most common in large breeds, especially

text: Great Dane

text: s and

text: Doberman Pinscher

text: s. In horses, it is not linked to a particular breed, though it is most often seen in tall, race-bred horses of

text: Thoroughbred

text: or

text: Standardbred

text: ancestry. It is most likely inherited to at least some extent in dogs and horses.

text: David Attenborough embarks on an epic 500-million-year journey to unravel the incredible rise of the vertebrates. The evolution of animals with backbones is one of the greatest stories in natural history. To tell this story, David presents explosive new fossil evidence from China, a region he has long dreamt of exploring and the frontier of modern paleontological research. He reveals how vertebrates came to be the dominant form of animal life, and why humans are the heirs to a magnificent evolutionary heritage.

text: Actinopterygians are divided into the subclasses Chondrostei and Neopterygii. The Neopterygii, in turn, are divided into the infraclasses Holostei and Teleostei. During the Mesozoic and Cenozoic the teleosts in particular diversified widely, and as a result, 96% of all known fish species are teleosts. The cladogram shows the major groups of actinopterygians and their relationship to the terrestrial vertebrates (tetrapods) that evolved from a related group of fish. Approximate dates are from Near et al., 2012.

text: Actinopterygians are divided into the subclasses

text: Chondrostei

text: and

text: Neopterygii

text: . The

text: Neopterygii

text: , in turn, are divided into the infraclasses

text: Holostei

text: and

text: Teleostei

text: . During the

text: Mesozoic

text: and

text: Cenozoic

text: the teleosts in particular diversified widely, and as a result, 96% of all known fish species are teleosts. The

text: cladogram

text: shows the major groups of actinopterygians and their relationship to the terrestrial vertebrates (tetrapods) that evolved from a related group of fish. Approximate dates are from Near et al., 2012.

text: Cartilage is a thin, elastic tissue that protects the bone and makes certain that the joint surfaces can slide easily over each other. Cartilage ensures supple knee movement. There are two types of joint cartilage in the knees: fibrous cartilage (the meniscus) and hyaline cartilage. Fibrous cartilage has tensile strength and can resist pressure. Hyaline cartilage covers the surface along which the joints move. Cartilage will wear over the years. Cartilage has a very limited capacity for self-restoration. The newly formed tissue will generally consist of a large part of fibrous cartilage of lesser quality than the original hyaline cartilage. As a result, new cracks and tears will form in the cartilage over time.

text: Cartilage

text: is a thin, elastic

text: tissue

text: that protects the

text: bone

text: and makes certain that the

text: joint

text: surfaces can slide easily over each other. Cartilage ensures supple knee movement. There are two types of joint cartilage in the knees: fibrous cartilage (the

text: meniscus

text: ) and

text: hyaline cartilage

text: . Fibrous cartilage has tensile strength and can resist pressure. Hyaline cartilage covers the surface along which the joints move. Cartilage will wear over the years. Cartilage has a very limited capacity for self-restoration. The newly formed tissue will generally consist of a large part of fibrous cartilage of lesser quality than the original hyaline cartilage. As a result, new cracks and tears will form in the cartilage over time.

text: Several fossil specimens show a high degree of preservation, with intact scales, pigmentation, claw sheaths, cartilage, and small bones. The orbitospenoids are present in one specimen as two small crescent-shaped bones. These bones support the cartilage and membrane that makes up the braincase, and are rarely preserved in fossil lizards. Postcloacal or hemipenial bones are also known, which are part of the hemipenis in male individuals.

text: Several fossil specimens show a high degree of preservation, with intact scales, pigmentation, claw sheaths, cartilage, and small bones. The orbitospenoids are present in one specimen as two small crescent-shaped bones. These bones support the cartilage and membrane that makes up the

text: braincase

text: , and are rarely preserved in fossil lizards. Postcloacal or hemipenial bones are also known, which are part of the

text: hemipenis

text: in male individuals.

text: As large-bodied vertebrates are increasingly lost from seed-dispersal networks, small-bodied seed dispersers (i.e. bats, birds, dung beetles) and seed predators (i.e. rodents) are affected. Defaunation leads to reduced species diversity. This is due to relaxed competition; small-bodied species normally compete with large-bodied vertebrates for food and other resources. As an area becomes defaunated, dominant small-bodied species take over, crowding out other similar species and leading to an overall reduced species diversity. The loss of species diversity is reflective of a larger loss of biodiversity, which has consequences for the maintenance of ecosystem services.

text: The sea urchin builds its spicules, the sharp, crystalline "bones" that constitute the animal’s endoskeleton, in the larval stage. The fully formed spicule is composed of a single crystal with an unusual morphology. It has no facets, and within 48 hours of fertilization, assumes a shape that looks much like the Mercedes-Benz logo.

text: The sea urchin builds its

text: spicules

text: , the sharp, crystalline "bones" that constitute the animal’s

text: endoskeleton

text: , in the

text: larval

text: stage. The fully formed spicule is composed of a single crystal with an unusual morphology. It has no facets, and within 48 hours of fertilization, assumes a shape that looks much like the

text: Mercedes-Benz

text: logo.

text: Plasmodium gemini is a parasite of the genus Plasmodium.  Like all Plasmodium species P. gemini has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Plasmodium gemini is a parasite of the genus

text: Plasmodium

text: .  Like all Plasmodium species P. gemini has both

text: vertebrate

text: and

text: insect

text: hosts. The vertebrate hosts for this parasite are

text: reptile

text: s.

text: Inside the skull, the two vertebral arteries join to form the basilar artery at the base of the Pons. The basilar artery is the main blood supply to the brainstem and connects to the Circle of Willis to potentially supply the rest of the brain if there is compromise to one of the carotids. At each cervical level, the vertebral artery sends branches to the surrounding musculature via the anterior spinal arteries.

text: Inside the skull, the two vertebral arteries join to form the

text: basilar artery

text: at the base of the

text: Pons

text: . The

text: basilar artery

text: is the main blood supply to the

text: brainstem

text: and connects to the

text: Circle of Willis

text: to potentially supply the rest of the brain if there is compromise to one of the

text: carotids

text: . At each cervical level, the vertebral artery sends branches to the surrounding musculature via the

text: anterior spinal arteries

text: The describing authors established some diagnostic traits. The front upper corner of the fenestra antorbitalis and the rear upper corner of the bony nostril are positioned at about the same height. The premaxilla shows a distinctive opening below and in front of the nostril. The rear upper process of the premaxilla touches the upper rim of the fenestra antorbitalis but not the front process of the lacrimal; both bones are separated by the nasal bone. The parietal approaches the frontal bone in length.  At the fourth and fifth neck vertebrae, the rear edge of the vertebral centrum forms a straight line between the postzygapophyses. The thigh bone is longer than the ilium.

text: The describing authors established some diagnostic traits. The front upper corner of the

text: fenestra antorbitalis

text: and the rear upper corner of the bony

text: nostril

text: are positioned at about the same height. The

text: premaxilla

text: shows a distinctive opening below and in front of the nostril. The rear upper process of the premaxilla touches the upper rim of the fenestra antorbitalis but not the front process of the

text: lacrimal

text: ; both bones are separated by the

text: nasal bone

text: . The

text: parietal

text: approaches the

text: frontal

text: bone in length.  At the fourth and fifth neck vertebrae, the rear edge of the vertebral centrum forms a straight line between the

text: postzygapophyses

text: . The thigh bone is longer than the

text: ilium

text: Among the Deuterostomia, there are a number of swimmers as well. Feather stars can swim by undulating their many arms . Salps move by pumping waters through their gelatinous bodies. The deuterosomes most evolved for swimming are found among the vertebrates, notably the fish.

text: Among the

text: Deuterostomia

text: , there are a number of swimmers as well.

text: Feather star

text: s can swim by undulating their many arms .

text: Salp

text: s move by pumping waters through their gelatinous bodies. The deuterosomes most evolved for swimming are found among the

text: vertebrate

text: s, notably the

text: fish

text: As is the case with most extinct sharks, this species is also known from fossil teeth and some fossilized vertebral centra. Shark skeleton is composed of cartilage and not bone, and cartilage rarely gets fossilized. Hence, fossils of C. angustidens are generally poorly preserved. To date, the best preserved specimen of this species have been excavated from New Zealand, which comprises 165 associated teeth and about 35 associated vertebral centra. This specimen is around 26 million years old. C. angustidens teeth are noted for their triangular crowns and small side cusps that are fully serrated. The serrations are very sharp and very well pronounced. C. angustidens was a widely distributed species with fossils found in North America, South America, Europe, Africa, New Zealand, Japan, Australia, and Malta.

text: As is the case with most

text: extinct

text: sharks, this species is also known from

text: fossil

text: teeth

text: and some fossilized

text: vertebral centra

text: . Shark

text: skeleton

text: is composed of

text: cartilage

text: and not

text: bone

text: , and cartilage rarely gets

text: fossilized

text: . Hence, fossils of C. angustidens are generally poorly preserved. To date, the best preserved specimen of this species have been excavated from

text: New Zealand

text: , which comprises 165 associated teeth and about 35 associated vertebral centra. This specimen is around 26 million years old. C. angustidens

text: teeth

text: are noted for their triangular crowns and small side cusps that are fully serrated. The serrations are very sharp and very well pronounced. C. angustidens was a widely distributed species with fossils found in

text: North America

text: South America

text: Europe

text: Africa

text: , New Zealand,

text: Japan

text: Australia

text: , and

text: Malta

text: The endothermy of Lampris guttatus gives them a major advantage at the depths where they live. Since they are relatively warm-blooded at those depths compared to the water around them, they can move more quickly to hunt prey. Most predators at such low depths do not have the energy to be able to move much and therefore must wait for prey to pass them.

text: The endothermy of Lampris guttatus gives them a major advantage at the depths where they live. Since they are relatively warm-blooded at those depths compared to the water around them, they can move more quickly to hunt

text: prey

text: . Most

text: predator

text: s at such low depths do not have the energy to be able to move much and therefore must wait for prey to pass them.

text: The major advantage of endothermy over ectothermy is decreased vulnerability to fluctuations in external temperature. Regardless of location (and hence external temperature), endothermy maintains a constant core temperature for optimum enzyme activity.

text: In order to be able to carry larger vertebrate prey, it has evolved disproportionately large feet. The legs and toes are a brownish-yellow with black talons. Females are 17.4 to 19 centimeters (6.8 to 7.5 inches) long, and males are generally smaller, measuring 15.2 to 17 centimeters (6 to 6.7 inches) in length. Females are about 67 to 77 grams, and males are 50 to 65 grams in weight.

text: In order to be able to carry larger

text: vertebrate

text: prey

text: , it has evolved disproportionately large feet. The legs and toes are a brownish-yellow with black

text: talons

text: . Females are 17.4 to 19 centimeters (6.8 to 7.5 inches) long, and males are generally smaller, measuring 15.2 to 17 centimeters (6 to 6.7 inches) in length. Females are about 67 to 77 grams, and males are 50 to 65 grams in weight.

text: The vertebral column consists of nine cervical vertebrae, fourteen dorsals and five sacrals. The number of tail vertebrae is unknown. The cervical vertebrae of the neck are strongly pneumatised. They possess pleurocoels at their sides and their insides are hollowed out by large air chambers. The neural spines of the cervical vertebrae are narrow in side view and decreased in width towards the rear: those of the eighth and ninth vertebrae were rod-like. At least the first three dorsal vertebrae of the back have pleurocoels as well. The dorsals are connected by robust hyposphene-hypantrum complexes. From the sixth vertebra onwards the neural spines abruptly become wider. The neural spines of the sacral vertebrae are not fused into a supraneural plate. The tail base is slightly oriented downwards. The caudal vertebrae of the tail base also show hyposphene-hypantrum complexes.

text: The vertebral column consists of nine cervical vertebrae, fourteen dorsals and five sacrals. The number of tail vertebrae is unknown. The cervical vertebrae of the neck are strongly pneumatised. They possess pleurocoels at their sides and their insides are hollowed out by large air chambers. The neural spines of the cervical vertebrae are narrow in side view and decreased in width towards the rear: those of the eighth and ninth vertebrae were rod-like. At least the first three dorsal vertebrae of the back have pleurocoels as well. The dorsals are connected by robust

text: hyposphene

text: hypantrum

text: complexes. From the sixth vertebra onwards the neural spines abruptly become wider. The neural spines of the sacral vertebrae are not fused into a supraneural plate. The tail base is slightly oriented downwards. The caudal vertebrae of the tail base also show hyposphene-hypantrum complexes.

text: Fish may have evolved from an animal similar to a coral-like sea squirt (a tunicate), whose larvae resemble early fish in important ways. The first ancestors of fish may have kept the larval form into adulthood (as some sea squirts do today), although perhaps the reverse is the case. Vertebrates, among them the first fishes, originated about 530 million years ago during the Cambrian explosion, which saw the rise in organism diversity.

text: Fish may have evolved from an animal similar to a coral-like

text: sea squirt

text: (a

text: tunicate

text: ), whose larvae resemble early fish in important ways. The first ancestors of fish may have

text: kept the larval form into adulthood

text: (as some sea squirts do today), although perhaps the reverse is the case.

text: Vertebrate

text: s, among them the first

text: fishes

text: , originated about 530 million years ago during the

text: Cambrian explosion

text: , which saw the rise in organism diversity.

text: Individual vertebrae of the human vertebral column can be felt and used as surface anatomy, with reference points are taken from the middle of the vertebral body. This provides anatomical landmarks that can be used to guide procedures such as a lumbar puncture and also as vertical reference points to describe the locations of other parts of human anatomy, such as the positions of organs.

text: Individual vertebrae of the human vertebral column can be felt and used as

text: surface anatomy

text: , with reference points are taken from the middle of the vertebral body. This provides

text: anatomical landmark

text: s that can be used to guide procedures such as a

text: lumbar puncture

text: and also as vertical reference points to describe the locations of other parts of human anatomy, such as the positions of

text: organs

text: The mechanism of mineral formation in bone is clearly distinct from the phylogenetically older process by which cartilage is mineralized: tetracycline does not label mineralized cartilage at narrow bands or in specific sites, but diffusely, in keeping with a passive mineralization mechanism.

text: The mechanism of mineral formation in bone is clearly distinct from the

text: phylogenetic

text: ally older process by which cartilage is mineralized: tetracycline does not label mineralized cartilage at narrow bands or in specific sites, but diffusely, in keeping with a passive mineralization mechanism.

text: The vertebral column in dinosaurs consists of the cervical (neck), dorsal (back), sacral (hips), and caudal (tail) vertebrae. Dinosaur vertebrae possess features known as pleurocoels, which are hollow depressions on the lateral portions of the vertebrae, which served to decrease the weight of these bones without sacrificing strength. Many researchers think that these pleurocoels were filled with air sacs, which would have further decreased weight. In sauropod dinosaurs, the largest known land vertebrates, pleurocoels may have reduced the animal's weight by over a ton in some instances, a handy evolutionary adaption in animals that grew to over 30 metres in length. In many hadrosaur and theropod dinosaurs, the caudal vertebrae were reinforced by ossified tendons. The presence of three or more sacral vertebrae, in association with the hip bones, is one of the defining characteristics of dinosaurs. The occipital condyle is a structure on the posterior part of a dinosaur's skull which articulates with the first cervical vertebra.

text: The vertebral column in

text: dinosaur

text: s consists of the cervical (neck), dorsal (back), sacral (hips), and caudal (tail) vertebrae. Dinosaur vertebrae possess features known as

text: pleurocoels

text: , which are hollow depressions on the lateral portions of the vertebrae, which served to decrease the weight of these bones without sacrificing strength. Many researchers think that these pleurocoels were filled with air sacs, which would have further decreased weight. In

text: sauropod

text: dinosaurs, the largest known land vertebrates, pleurocoels may have reduced the animal's weight by over a ton in some instances, a handy evolutionary adaption in animals that grew to over 30 metres in length. In many

text: hadrosaur

text: and

text: theropod

text: dinosaurs, the caudal vertebrae were reinforced by ossified tendons. The presence of three or more sacral vertebrae, in association with the hip bones, is one of the defining characteristics of dinosaurs. The

text: occipital condyle

text: is a structure on the posterior part of a dinosaur's skull which articulates with the first cervical vertebra.

text: Unlike jawed vertebrates, which have three semicircular canals in each inner ear, lampreys have only two and hagfishes just one. But the semicircular canal of hagfishes contains both stereocilia and a second class of hair cells, apparently a derived trait, whereas lampreys and other vertebrates have stereocilia only. Because the inner ear of hagfishes has two forms of sensory ampullae, their single semicircular canal is assumed to be a result of two semicircular canals that have merged into just one.

text: Unlike jawed vertebrates, which have three

text: semicircular canal

text: s in each inner ear, lampreys have only two and hagfishes just one. But the semicircular canal of hagfishes contains both

text: stereocilia

text: and a second class of hair cells, apparently a derived trait, whereas lampreys and other vertebrates have stereocilia only. Because the inner ear of hagfishes has two forms of sensory ampullae, their single semicircular canal is assumed to be a result of two semicircular canals that have merged into just one.

text: The term "fish" most precisely describes any non-tetrapod craniate (i.e. an animal with a skull and in most cases a backbone) that has gills throughout life and whose limbs, if any, are in the shape of fins. Unlike groupings such as birds or mammals, fish are not a single clade but a paraphyletic collection of taxa, including hagfishes, lampreys, sharks and rays, ray-finned fish, coelacanths, and lungfish. Indeed, lungfish and coelacanths are closer relatives of tetrapods (such as mammals, birds, amphibians, etc.) than of other fish such as ray-finned fish or sharks, so the last common ancestor of all fish is also an ancestor to tetrapods. As paraphyletic groups are no longer recognised in modern systematic biology, the use of the term "fish" as a biological group must be avoided.

text: The term "fish" most precisely describes any non-

text: tetrapod

text: craniate

text: (i.e. an animal with a skull and in most cases a backbone) that has

text: gill

text: s throughout life and whose limbs, if any, are in the shape of fins. Unlike groupings such as birds or

text: mammal

text: s, fish are not a single

text: clade

text: but a

text: paraphyletic

text: collection of

text: taxa

text: , including

text: hagfish

text: es,

text: lamprey

text: s,

text: sharks and rays

text: ray-finned fish

text: coelacanth

text: s, and

text: lungfish

text: . Indeed, lungfish and coelacanths are closer relatives of

text: tetrapod

text: s (such as

text: mammal

text: s, birds,

text: amphibians

text: , etc.) than of other fish such as

text: ray-finned fish

text: or sharks, so the

text: last common ancestor

text: of all fish is also an ancestor to tetrapods. As paraphyletic groups are no longer recognised in modern

text: systematic biology

text: , the use of the term "fish" as a biological group must be avoided.

text: The first jawed vertebrates appeared in the late Ordovician and became common in the Devonian, often known as the "Age of Fishes". The two groups of  bony fishes, the actinopterygii and sarcopterygii, evolved and became common. The Devonian also saw the demise of virtually all jawless fishes, save for lampreys and hagfish, as well as the Placodermi, a group of armoured fish that dominated much of the late Silurian. The Devonian also saw the rise of the first labyrinthodonts, which was a transitional between fishes and amphibians.

text: The first

text: jawed vertebrates

text: appeared in the late

text: Ordovician

text: and became common in the

text: Devonian

text: , often known as the "Age of Fishes". The two groups of

text: bony fishes

text: , the

text: actinopterygii

text: and

text: sarcopterygii

text: , evolved and became common. The Devonian also saw the demise of virtually all jawless fishes, save for lampreys and hagfish, as well as the

text: Placodermi

text: , a group of armoured fish that dominated much of the late

text: Silurian

text: . The Devonian also saw the rise of the first

text: labyrinthodonts

text: , which was a transitional between fishes and

text: amphibians

text: As clearly seen in the lamprey, Cyclostome also has a pair of cartilaginous rods in the embryonic head which is similar to the trabecular cartilages in jawed vertebrates.However, in 1916, Alexej Nikolajevich Sewertzoff pointed out that the cranial base of the lamprey is exclusively originated from the paraxial mesoderm. Then in 1948, Alf Johnels reported the detail of the skeletogenesis of the lamprey, and showed that the “trabecular cartilages” in lamprey appear just beside the notochord, in a similar position to the parachordal cartilages in jawed vertebrates. Recent experimental studies also showed that the cartilages are derived from the head mesoderm. Today, the “trabecular cartilages” in the Cyclostome is no longer considered to be the homologue of the trabecular in the jawed vertebrates: the (true) trabecular cartilages were firstly acquired in the Gnathostome lineage.

text: As clearly seen in the

text: lamprey

text: Cyclostome

text: also has a pair of cartilaginous rods in the embryonic head which is similar to the trabecular cartilages in jawed vertebrates.However, in 1916,

text: Alexej Nikolajevich Sewertzoff

text: pointed out that the cranial base of the lamprey is exclusively originated from the paraxial mesoderm. Then in 1948,

text: Alf Johnels

text: reported the detail of the skeletogenesis of the lamprey, and showed that the “trabecular cartilages” in lamprey appear just beside the notochord, in a similar position to the parachordal cartilages in jawed vertebrates. Recent experimental studies also showed that the cartilages are derived from the head mesoderm. Today, the “trabecular cartilages” in the Cyclostome is no longer considered to be the homologue of the trabecular in the jawed vertebrates: the (true) trabecular cartilages were firstly acquired in the Gnathostome lineage.

text: While most of these were open-water fishes, one group, the Elpistostegalians, adapted to life in the shallows. They evolved flat bodies for movement in very shallow water, and the pectoral and pelvic fins took over as the main propulsion organs. Most median fins disappeared, leaving only a protocercal tailfin. Since the shallows were subject to occasional oxygen deficiency, the ability to breathe atmospheric air with the swim bladder became increasingly important. The spiracle became large and prominent, enabling these fishes to draw air.

text: While most of these were open-water fishes, one group, the

text: Elpistostegalia

text: ns, adapted to life in the shallows. They evolved flat bodies for movement in very shallow water, and the pectoral and pelvic fins took over as the main propulsion organs. Most median fins disappeared, leaving only a

text: protocercal

text: tailfin. Since the shallows were subject to occasional oxygen deficiency, the ability to breathe atmospheric air with the swim bladder became increasingly important. The spiracle became large and prominent, enabling these fishes to draw air.

text: Professor Philip S. Bolton of the School of Biomedical Sciences at University of Newcastle, Australia writes in Journal of Manipulative and Physiological Therapeutics, "The traditional chiropractic vertebral subluxation hypothesis proposes that vertebral misalignment cause illness, disease, or both. This hypothesis remains controversial." His objective was, "To briefly review and update experimental evidence concerning reflex effects of vertebral subluxations, particularly concerning peripheral nervous system responses to vertebral subluxations. Data source: Information was obtained from chiropractic or, scientific peer-reviewed literature concerning human or animal studies of neural responses to vertebral subluxation, vertebral displacement or movement, or both." He concluded, "Animal models suggest that vertebral displacements and putative vertebral subluxations may modulate activity in group I to IV afferent nerves. However, it is not clear whether these afferent nerves are modulated during normal day-to-day activities of living and, if so, what segmental or whole-body reflex effects they may have."

text: Professor Philip S. Bolton of the School of Biomedical Sciences at

text: University of Newcastle, Australia

text: writes in

entity_name: Journal of Manipulative and Physiological Therapeutics

text: Journal of Manipulative and Physiological Therapeutics

text: , "The traditional chiropractic vertebral subluxation hypothesis proposes that vertebral misalignment cause illness, disease, or both. This hypothesis remains controversial." His objective was, "To briefly review and update experimental evidence concerning reflex effects of vertebral subluxations, particularly concerning peripheral nervous system responses to vertebral subluxations. Data source: Information was obtained from chiropractic or, scientific peer-reviewed literature concerning human or animal studies of neural responses to vertebral subluxation, vertebral displacement or movement, or both." He concluded, "Animal models suggest that vertebral displacements and putative vertebral subluxations may modulate activity in group I to IV afferent nerves. However, it is not clear whether these afferent nerves are modulated during normal day-to-day activities of living and, if so, what segmental or whole-body reflex effects they may have."

text: The spinal canal  (or vertebral canal or spinal cavity) is the space in the vertebral column formed by the vertebrae through which the spinal cord passes. It is a process of the dorsal body cavity. This canal is enclosed within the vertebral foramen of the vertebrae. In the intervertebral spaces, the canal is protected by the ligamentum flavum posteriorly and the posterior longitudinal ligament anteriorly.

text: The spinal canal  (or vertebral canal or spinal cavity) is the space in the

text: vertebral column

text: formed by the

text: vertebra

text: e through which the

text: spinal cord

text: passes. It is a process of the

text: dorsal body cavity

text: . This canal is enclosed within the

text: vertebral foramen

text: of the

text: vertebrae

text: . In the intervertebral spaces, the canal is protected by the

text: ligamentum flavum

text: posteriorly and the

text: posterior longitudinal ligament

text: anteriorly.

text: Information about the direct neuronal regulation of metabolic processes and circadian rhythm-controlled behaviors is not well known among either endothermic or ectothermic vertebrates, although extensive research has been done on the SCN in model animals such as the mammalian mouse and ectothermic reptiles, in particular, lizards. The SCN is known to be involved not only in photoreception through innervation from the retinohypothalamic tract but also in thermoregulation of vertebrates capable of homeostasis, as well as regulating locomotion and other behavioral outputs of the circadian clock within ectothermic vertebrates. The behavioral differences between both classes of vertebrates, when compared to the respective structures and properties of the SCN and various other nuclei proximate to the hypothalamus, provide insight into how these behaviors are the consequence of differing circadian regulation. Ultimately, many neuroethological studies must be done to completely ascertain the direct and indirect roles of the SCN on circadian-regulated behaviors of vertebrates.

text: Information about the direct neuronal regulation of metabolic processes and

text: circadian rhythm

text: -controlled behaviors is not well known among either

text: endothermic

text: or

text: ectothermic

text: vertebrates

text: , although extensive research has been done on the SCN in model animals such as the mammalian mouse and ectothermic reptiles, in particular, lizards. The SCN is known to be involved not only in

text: photoreception

text: through innervation from the

text: retinohypothalamic tract

text: but also in thermoregulation of vertebrates capable of

text: homeostasis

text: , as well as regulating locomotion and other behavioral outputs of the circadian clock within ectothermic vertebrates. The behavioral differences between both classes of vertebrates, when compared to the respective structures and properties of the SCN and various other nuclei proximate to the

text: hypothalamus

text: , provide insight into how these behaviors are the consequence of differing circadian regulation. Ultimately, many neuroethological studies must be done to completely ascertain the direct and indirect roles of the SCN on circadian-regulated behaviors of vertebrates.

text: The amount of this water that is retained in animals is affected by several factors. Water amounts vary with the age of the animal. The older the vertebrate animal, the higher its relative bone mass and the lower its body water content.

text: The amount of this water that is retained in animals is affected by several factors. Water amounts vary with the age of the animal. The older the

text: vertebrate

text: animal, the higher its relative bone mass and the lower its body water content.

text: The brain contains several mechanisms involved in vision. Consider two systems in the brain which evolved at different times. The first that evolved is more primitive and resembles the visual system of animals such as fish and frogs. The second to evolve is more complex and is possessed by mammals. The second system seems to be the one that is responsible for our ability to perceive the world around us and the first system is devoted mainly to controlling eye movements and orienting our attention to sudden movements in our periphery. Patients with blindsight have damage to the second, "mammalian" visual system (the visual cortex of the brain and some of the nerve fibers that bring information to it from the eyes). This phenomenon shows how, after the more complex visual system is damaged, people can use the primitive visual system of their brains to guide hand movements towards an object even though they can't see what they are reaching for. Hence, visual information can control behavior without producing a conscious sensation. This ability of those with blindsight to see objects that they are unconscious of suggests that consciousness is not a general property of all parts of the brain; yet it suggests that only certain parts of the brain play a special role in consciousness.

text: The

text: brain

text: contains several mechanisms involved in

text: vision

text: . Consider two systems in the brain which evolved at different times. The first that evolved is more primitive and resembles the visual system of animals such as fish and frogs. The second to evolve is more complex and is possessed by mammals. The second system seems to be the one that is responsible for our ability to perceive the world around us and the first system is devoted mainly to controlling eye movements and orienting our attention to sudden movements in our periphery. Patients with blindsight have damage to the second, "mammalian" visual system (the

text: visual cortex

text: of the brain and some of the

text: nerve fibers

text: that bring information to it from the

text: eyes

text: ). This phenomenon shows how, after the more complex visual system is damaged, people can use the primitive visual system of their brains to guide hand movements towards an object even though they can't see what they are reaching for. Hence, visual information can control behavior without producing a

text: conscious

text: sensation. This ability of those with blindsight to see objects that they are unconscious of suggests that consciousness is not a general property of all parts of the brain; yet it suggests that only certain parts of the brain play a special role in consciousness.

text: Although a hangman's fracture is unstable, survival from this fracture is relatively common, as the fracture itself tends to expand the spinal canal at the C2 level. It is not unusual for patients to walk in for treatment and have such a fracture discovered on X-rays. Only if the force of the injury is severe enough that the vertebral body of C2 is severely subluxed from C3 does the spinal cord become crushed, usually between the vertebral body of C3 and the posterior elements of C1 and C2.

text: There is an elevated number of flora species registered (508) that include rare and threatened Iberian endemics. These plants include hygrophilous forests, natural pastures and lagoon systems that are relevant for the natural conservation and biodiversity. Although the area is small, it has a large diversity of vertebrates; 9 species of freshwater and migratory fish, 13 species of amphibians, 11 types of reptiles, 41 species of mammals and 144 migratory or nesting bird species occupy that wetlands at any time. Of these, 25 species of terrestrial and freshwater vertebrates are classified as priority of conservation and associated with humid zones.

text: Because of the many similarities between vertebrate and invertebrate systems, especially with regards to basic principles of neuronal function, invertebrate model systems such as the crustacean stomatogastric nervous system continue to provide key insight into how neural circuits operate in the numerically larger and less accessible vertebrate CNS.

text: Because of the many similarities between vertebrate and invertebrate systems, especially with regards to basic principles of neuronal function, invertebrate model systems such as the

text: crustacea

text: n stomatogastric nervous system continue to provide key insight into how neural circuits operate in the numerically larger and less accessible vertebrate CNS.

text: The squamosal is a bone of the head of higher vertebrates. It is the principal component of the cheek region in the skull, lying below the temporal series and otic notch and bounded anteriorly by the postorbital. Posteriorly, the squamosal articulates with the posterior elements of the palatal complex, namely the quadrate and pterygoid. The squamosal is bordered anteroventrally by the jugal and ventrally by the quadratojugal.

text: The squamosal is a bone of the head of

text: higher vertebrate

text: s. It is the principal component of the cheek region in the skull, lying below the temporal series and

text: otic notch

text: and bounded anteriorly by the

text: postorbital

text: . Posteriorly, the squamosal articulates with the posterior elements of the palatal complex, namely the

text: quadrate

text: and

text: pterygoid

text: . The squamosal is bordered anteroventrally by the

text: jugal

text: and ventrally by the

text: quadratojugal

text: Three homologous genes have evolved in vertebrates, encoding three muscle type specific isoforms of TnT. Each of the TnT isoform genes is linked to one of the three troponin I isoform genes encoding the inhibitory subunit of the troponin complex, in chromosomal DNA to form three gene pairs: The fast skeletal muscle TnI (fsTnI)-fsTnT, ssTnI-cardiac (cTnT) and cTnI-ssTnT gene pairs. Sequence and epitope conservation studies suggested that genes encoding the muscle type specific TnT and TnI isoforms may have evolved from duplications of a fsTnI-like-fsTnT-like gene pair. Evolutionary lineage of the three TnI-TnT gene pairs shows that cTnI-ssTnT is the newest and most closely linked.

text: Three

text: homologous gene

text: s have evolved in vertebrates, encoding three muscle type specific

text: isoforms

text: of TnT. Each of the TnT isoform genes is linked to one of the three troponin I isoform genes encoding the inhibitory subunit of the troponin complex, in chromosomal DNA to form three gene pairs: The fast skeletal muscle TnI (fsTnI)-fsTnT, ssTnI-cardiac (cTnT) and cTnI-ssTnT gene pairs. Sequence and epitope conservation studies suggested that genes encoding the muscle type specific TnT and TnI isoforms may have evolved from duplications of a fsTnI-like-fsTnT-like gene pair. Evolutionary lineage of the three TnI-TnT gene pairs shows that cTnI-ssTnT is the newest and most closely linked.

text: It is one of a small number of vertebrate species that are known to reproduce by parthenogenesis.

text: It is one of a small number of

text: vertebrate

text: species that are known to reproduce by

text: parthenogenesis

text: There are broad correlations between different types of diversity. For example, there is a close link between vertebrate taxonomic and ecological diversity.

text: Reptiles are classified according to the pattern of fenestration in the temporal region of the skull. Testudines are placed in the subclass Anapsida because they lack fenestration. There are suggestions that this lack of fenestration is a secondary characteristic and that turtles belong in Diapsida.Both sides cite strong evidence, and the conflict has yet to be resolved. The shell of testudines distinguishes them from other vertebrates. The shell is not an exoskeleton, but a modified ribcage and part of the vertebral column. Because of the shell, the pectoral and pelvic girdles are located within the ribcage. The limb bones are also modified to accommodate to the shell.

text: Reptiles are classified according to the pattern of

text: fenestration

text: in the temporal region of the

text: skull

text: . Testudines are placed in the subclass

text: Anapsida

text: because they lack fenestration. There are suggestions that this lack of fenestration is a secondary characteristic and that turtles belong in

text: Diapsida

text: .Both sides cite strong evidence, and the conflict has yet to be resolved. The shell of testudines distinguishes them from other vertebrates. The shell is not an

text: exoskeleton

text: , but a modified

text: ribcage

text: and part of the

text: vertebral column

text: . Because of the shell, the pectoral and pelvic girdles are located within the ribcage. The limb bones are also modified to accommodate to the shell.

text: The formation of bone is called ossification. During the fetal stage of development this occurs by two processes, Intramembranous ossification and endochondral ossification. Intramembranous ossification involves the creation of bone from connective tissue, whereas in the process of endochondral ossification bone is created from cartilage.

text: The formation of bone is called

text: ossification

text: . During the fetal stage of development this occurs by two processes,

text: Intramembranous ossification

text: and

text: endochondral ossification

text: . Intramembranous ossification involves the creation of bone from

text: connective tissue

text: , whereas in the process of endochondral ossification bone is created from

text: cartilage

text: The European Association of Vertebrate Palaeontologists (EAVP) is a society for the advancement of vertebrate palaeontology in Europe.

text: The European Association of Vertebrate Palaeontologists (EAVP) is a society for the advancement of

text: vertebrate palaeontology

text: in

text: Europe

text: Fish are very diverse animals and can be categorised in many ways. This article is an overview of some of ways in which fish are categorised. Although most fish species have probably been discovered and described, about 250 new ones are still discovered every year. According to FishBase, 33,100 species of fish had been described by April 2015. That is more than the combined total of all other vertebrate species: mammals, amphibians, reptiles and birds.

text: Fish

text: are very diverse animals and can be categorised in many ways. This article is an overview of some of ways in which fish are categorised. Although most fish

text: species

text: have probably been discovered and described, about 250 new ones are still discovered every year. According to

text: FishBase

text: , 33,100 species of fish had been described by April 2015. That is more than the combined total of all other

text: vertebrate

text: species:

text: mammal

text: s,

text: amphibian

text: s,

text: reptile

text: s and

text: bird

text: s.

text: Tenascin C (TN-C) is a glycoprotein that in humans is encoded by the TNC gene. It is expressed in the extracellular matrix of various tissues during development, disease or injury, and in restricted neurogenic areas of the central nervous system. Tenascin-C is the founding member of the tenascin protein family. In the embryo it is made by migrating cells like the neural crest; it is also abundant in developing tendons, bone and cartilage.

text: Tenascin C (TN-C) is a

text: glycoprotein

text: that in humans is encoded by the TNC

text: gene

text: . It is expressed in the

text: extracellular matrix

text: of various tissues during development, disease or injury, and in restricted

text: neurogenic

text: areas of the central nervous system. Tenascin-C is the founding member of the

text: tenascin

text: protein family

text: . In the embryo it is made by migrating cells like the neural crest; it is also abundant in developing tendons, bone and cartilage.

text: The anatomic connections between the cerebral and vertebral venous systems was accurately depicted in 1819 by Gilbert Breschet, a French physician later to become Professor of Anatomy at Faculté de médecine de Paris. However, the significance and physiology of this venous complex remained obscure for more than a century, until the seminal work of Oscar Batson. Batson, a Professor of Anatomy at the University of Pennsylvania, in 1940 detailed the anatomy and physiology of the cerebrospinal venous system and its role in the spread of metastases. Batson’s work remains primarily known for its accurate depiction of the vertebral venous system as the route of metastasis of cancer from the prostate to the spine, and the vertebral venous system is often referred to as Batson venous plexus or Batson’s plexus. It is less commonly recognized that Batson’s detailed experiments also demonstrated the direct anatomic connection between the vertebral and cerebral venous system, an anatomical and physiological fact that was later confirmed by others.  It was later recognized that the cerebrospinal venous system represents a main route for efflux of venous blood from the brain. Modern imaging methodology, including MR scanning, have detailed the anastomoses of the cerebral and spinal venous systems in the suboccipital region. Batson, and others had recognized that blood flow in the cerebrospinal venous system was bi-directional, a unique feature that was enabled by a general lack of venous valves in these venous plexuses. This bi-directional flow was thought to have physiologic significance with regard to the maintenance of pressure hemostasis within the cranium with changes in posture. The terms “cerebrospinal venous system” and “CSVS” were coined in a 2006 review  that has itself been cited in a number of subsequent articles and reviews.

text: The anatomic connections between the cerebral and vertebral venous systems was accurately depicted in 1819 by

text: Gilbert Breschet

text: , a French physician later to become Professor of Anatomy at Faculté de médecine de Paris. However, the significance and physiology of this venous complex remained obscure for more than a century, until the seminal work of Oscar Batson. Batson, a Professor of Anatomy at the University of Pennsylvania, in 1940 detailed the anatomy and physiology of the cerebrospinal venous system and its role in the spread of metastases. Batson’s work remains primarily known for its accurate depiction of the vertebral venous system as the route of

text: metastasis

text: of cancer from the prostate to the spine, and the vertebral venous system is often referred to as

text: Batson venous plexus

text: or Batson’s plexus. It is less commonly recognized that Batson’s detailed experiments also demonstrated the direct anatomic connection between the vertebral and cerebral venous system, an anatomical and physiological fact that was later confirmed by others.  It was later recognized that the cerebrospinal venous system represents a main route for efflux of venous blood from the brain. Modern imaging methodology, including

text: MR scanning

text: , have detailed the

text: anastomoses

text: of the cerebral and spinal venous systems in the

text: suboccipital

text: region. Batson, and others had recognized that blood flow in the cerebrospinal venous system was bi-directional, a unique feature that was enabled by a general lack of venous valves in these venous plexuses. This bi-directional flow was thought to have physiologic significance with regard to the maintenance of pressure

text: hemostasis

text: within the cranium with changes in posture. The terms “cerebrospinal venous system” and “CSVS” were coined in a 2006 review  that has itself been cited in a number of subsequent articles and reviews.

text: It extends throughout the entire length of the future vertebral column, and reaches as far as the anterior end of the midbrain, where it ends in a hook-like extremity in the region of the future dorsum sellae of the sphenoid bone. Initially it exists between the neural tube and the endoderm of the yolk-sac, but soon becomes separated from them by the mesoderm, which grows medially and surrounds it. From the mesoderm surrounding the neural tube and notochord, the skull, vertebral column, and the membranes of the brain and medulla spinalis are developed.

text: It extends throughout the entire length of the future vertebral column, and reaches as far as the anterior end of the

text: midbrain

text: , where it ends in a hook-like extremity in the region of the future

text: dorsum sellae

text: of the

text: sphenoid bone

text: . Initially it exists between the neural tube and the endoderm of the yolk-sac, but soon becomes separated from them by the

text: mesoderm

text: , which grows medially and surrounds it. From the mesoderm surrounding the neural tube and notochord, the

text: skull

text: , vertebral column, and the

text: membrane

text: s of the

text: brain

text: and

text: medulla spinalis

text: are developed.

text: Besides his "Text-book of Human Anatomy"(1889) for which he is best known, he was the author of "Introduction to Animal Morphology"(1876) and "Morphology of Vertebrate Animals" (1878) as well as of numerous papers on animal, morphology, human anatomy and small text-books for students. He was a man of remarkable versatility, being an able mathematician as well as versed in archæology, Egyptology and draughtsmanship. Like his cousin, Sir Donald Macalister, he was a proficient linguist, having knowledge of fourteen languages.

text: Besides his "Text-book of Human Anatomy"(1889) for which he is best known, he was the author of "Introduction to Animal Morphology"(1876) and "Morphology of Vertebrate Animals" (1878) as well as of numerous papers on animal, morphology, human anatomy and small text-books for students. He was a man of remarkable versatility, being an able mathematician as well as versed in archæology, Egyptology and draughtsmanship. Like his cousin, Sir

text: Donald Macalister

text: , he was a proficient linguist, having knowledge of fourteen languages.

text: The frontal eye consists of a pigment cup, a group of putative photoreceptor cells (termed Row 1), three rows of neurons (Rows 2-4), and glial cells. The frontal eye, which expresses the PAX6 gene, has been proposed as the homolog of vertebrate paired eyes, the pigment cup as the homolog of the RPE (retinal pigment epithelium), the putative photoreceptors as homologs of vertebrate rods and cones, and Row 2 neurons as homologs of the retinal ganglion cells.

text: The frontal eye consists of a pigment cup, a group of putative photoreceptor cells (termed Row 1), three rows of neurons (Rows 2-4), and

text: glial cells

text: . The frontal eye, which expresses the

text: gene, has been proposed as the homolog of vertebrate paired eyes, the pigment cup as the homolog of the RPE (

text: retinal pigment epithelium

text: ), the putative photoreceptors as homologs of vertebrate

text: rods

text: and

text: cones

text: , and Row 2 neurons as homologs of the

text: retinal ganglion cells

text: Molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, and so also are vertebrates in a monophyletic sense. Others consider them a sister group of vertebrates in the common taxon of craniata.

text: Molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, and so also are vertebrates in a

text: monophyletic

text: sense. Others consider them a sister group of vertebrates in the common taxon of craniata.

text: Vertebrates

text: Vertebrates

text: Daza et al. (2016) described a small (10,6 mm in snout-vent length), probably neonatal lizard preserved in the Cretaceous (Albian-Cenomanian boundary) amber from Myanmar. The authors noted that the lizard has "short and wide skull, large orbits, elongated and robust lingual process, frontal with parallel margins, incipient prefrontal boss, reduced vomers, absent retroarticular process, low presacral vertebral count (between 15 and 17) and extremely short, curled tail"; the authors considered these traits to be indicative of the lizard's affiliation with Chamaeleonidae. The phylogenetic analysis conducted by the authors indicated that the lizard was a stem-chamaeleonid.

text: Daza et al. (2016) described a small (10,6 mm in snout-vent length), probably

text: neonatal

text: lizard preserved in the Cretaceous (

text: Albian

text: Cenomanian

text: boundary) amber from

text: Myanmar

text: . The authors noted that the lizard has "short and wide skull, large orbits, elongated and robust lingual process, frontal with parallel margins, incipient prefrontal boss, reduced vomers, absent retroarticular process, low presacral vertebral count (between 15 and 17) and extremely short, curled tail"; the authors considered these traits to be indicative of the lizard's affiliation with Chamaeleonidae. The phylogenetic analysis conducted by the authors indicated that the lizard was a

text: stem

text: -chamaeleonid.

text: The two transverse processes, one on each side of the vertebral body project from either side at the point where the lamina joins the pedicle, between the superior and inferior articular processes. They also serve for the attachment of muscles and ligaments, in particular the intertransverse ligaments. There is a facet on each of the transverse processes of thoracic vertebrae which articulates with the tubercle of the rib. A facet on each side of the thoracic vertebral body articulates with the head of the rib. There are superior and inferior articular facet joints on each side of the vertebra, which serve to restrict the range of movement possible. These facets are joined by a thin portion of the vertebral arch called the pars interarticularis.

text: The two transverse processes, one on each side of the vertebral body project from either side at the point where the lamina joins the

text: pedicle

text: , between the superior and inferior

text: articular processes

text: . They also serve for the attachment of muscles and ligaments, in particular the

text: intertransverse ligament

text: s. There is a facet on each of the transverse processes of thoracic vertebrae which articulates with the

text: tubercle of the rib

text: . A facet on each side of the thoracic vertebral body articulates with the

text: head of the rib

text: . There are superior and inferior

text: articular

text: facet joint

text: s on each side of the vertebra, which serve to restrict the range of movement possible. These facets are joined by a thin portion of the vertebral arch called the

text: pars interarticularis

text: Vertebrate dentition originated from a folding in of the placoderm's armor, evolving into the familiar condition of living reptiles, amphibians, and fish: a long row of pointed or sharp-sided, undifferentiated teeth (homodont) that are completely replaceable. The mammalian pattern is significantly different. The teeth in the upper and lower jaws in mammals have evolved a close-fitting relationship such that they operate together as a unit. "They occlude, that is, the chewing surfaces of the teeth are so constructed that the upper and lower teeth are able to fit precisely together, cutting, crushing, grinding or shearing the food caught between."

text: Vertebrate dentition originated from a folding in of the

text: placoderm

text: 's armor, evolving into the familiar condition of living

text: reptile

text: s,

text: amphibian

text: s, and

text: fish

text: : a long row of pointed or sharp-sided, undifferentiated teeth (homodont) that are completely replaceable. The mammalian pattern is significantly different. The teeth in the upper and lower jaws in mammals have evolved a close-fitting relationship such that they operate together as a unit. "They occlude, that is, the chewing surfaces of the teeth are so constructed that the upper and lower teeth are able to fit precisely together, cutting, crushing, grinding or shearing the food caught between."

text: Because many homeothermic animals use enzymes which are specialized for a narrow range of body temperatures, hypothermia rapidly leads to torpor and then death.Additionally, homeothermy obtained from endothermy is a high energy strategy and many environments will offer lower carrying capacity to these organisms. In cold weather the energy expenditure to maintain body temperature accelerates starvation and may lead to death.

text: Because many homeothermic animals use enzymes which are specialized for a narrow range of body temperatures,

text: hypothermia

text: rapidly leads to

text: torpor

text: and then death.Additionally, homeothermy obtained from endothermy is a high energy strategy and many environments will offer lower

text: carrying capacity

text: to these organisms. In cold weather the energy expenditure to maintain body temperature accelerates starvation and may lead to death.

text: Vertebrates  comprise all species of animals within the subphylum Vertebrata  (chordates with backbones). Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 64,000 species described. Vertebrates include the jawless fish and the jawed vertebrates, which include the cartilaginous fish (sharks and rays) and the bony fish.

text: Vertebrates  comprise all species of

text: animal

text: s within the

text: subphylum

text: Vertebrata  (

text: chordates

text: with

text: backbones

text: ). Vertebrates represent the overwhelming majority of the

text: phylum

text: Chordata

text: , with currently about 64,000

text: species

text: described. Vertebrates include the

text: jawless fish

text: and the

text: jawed vertebrates

text: , which include the

text: cartilaginous fish

text: shark

text: s and

text: rays

text: ) and the

text: bony fish

text: There are different ligaments involved in the holding together of the vertebrae in the column, and in the column's movement. The anterior and posterior longitudinal ligaments extend the length of the vertebral column along the front and back of the vertebral bodies. The interspinous ligaments connect the adjoining spinous processes of the vertebrae. The supraspinous ligament extends the length of the spine running along the back of the spinous processes, from the sacrum to the seventh cervical vertebra. From there it is continuous with the nuchal ligament.

text: There are different ligaments involved in the holding together of the vertebrae in the column, and in the column's movement. The

text: anterior

text: and

text: posterior longitudinal ligament

text: s extend the length of the vertebral column along the front and back of the vertebral bodies. The

text: interspinous ligament

text: s connect the adjoining spinous processes of the vertebrae. The

text: supraspinous ligament

text: extends the length of the spine running along the back of the spinous processes, from the sacrum to the

text: seventh

text: cervical vertebra

text: . From there it is continuous with the

text: nuchal ligament

text: The transition from an aquatic, lobe-finned fish to an air-breathing amphibian was a significant and fundamental one in the evolutionary history of the vertebrates. For an organism to live in a gravity-neutral aqueous environment, then colonize one that requires an organism to support its entire weight and possess a mechanism to mitigate dehydration, required significant adaptations or exaptations within the overall body plan, both in form and in function. Eryops, an example of an animal that made such adaptations, refined many of the traits found in its fish ancestors. Sturdy limbs supported and transported its body while out of water. A thicker, stronger backbone prevented its body from sagging under its own weight. Also, through the reshaping of vestigial fish jaw bones, a rudimentary middle ear began developing to connect to the piscine inner ear, allowing Eryops to amplify, and so better sense, airborne sound.

text: The transition from an aquatic, lobe-finned fish to an air-breathing amphibian was a significant and fundamental one in the evolutionary history of the

text: vertebrate

text: s. For an organism to live in a

text: gravity

text: -neutral aqueous environment, then colonize one that requires an organism to support its entire weight and possess a mechanism to mitigate dehydration, required significant adaptations or exaptations within the overall

text: body plan

text: , both in form and in function.

text: Eryops

text: , an example of an animal that made such adaptations, refined many of the traits found in its fish ancestors. Sturdy

text: limb

text: s supported and transported its body while out of water. A thicker, stronger

text: backbone

text: prevented its body from sagging under its own weight. Also, through the reshaping of vestigial fish jaw bones, a rudimentary middle ear began developing to connect to the

text: piscine inner ear

text: , allowing Eryops to amplify, and so better sense, airborne

text: sound

text: A spinal fracture, also called a vertebral fracture or a broken back, is a fracture affecting the vertebrae of the spinal column. Types of spinal fracture include vertebral compression fracture and burst fracture,  cervical fracture, Jefferson fracture, Hangman's fracture, Flexion teardrop fracture, Clay-shoveler fracture, Chance fracture and Holdsworth fracture.

text: A spinal fracture, also called a vertebral fracture or a broken back, is a

text: fracture

text: affecting the

text: vertebrae

text: of the

text: spinal column

text: . Types of spinal fracture include

text: vertebral compression fracture

text: and

text: burst fracture

text: cervical fracture

text: Jefferson fracture

text: Hangman's fracture

text: Flexion teardrop fracture

text: Clay-shoveler fracture

text: Chance fracture

text: and

text: Holdsworth fracture

text: Two fossil specimens of Sclerothorax were discovered in the German state of Hesse in the 1920s. German paleontologist Friedrich von Huene studied the remains and named the new genus and species Sclerothorax hypselonotus in 1932. The holotype specimen preserved only the vertebral column, but was identifiable as a temnospondyl by its rhachitomous vertebrae and as a new species by its tall neural spines. Huene's second specimen included a complete skull, pectoral girdle, and back portion of the dorsal vertebral column that was also clearly a temnospondyl. However, it was not apparent that the specimen belonged to the same species as the first until Huene exposed more of the crushed vertebrae and found that they were similar to those of his first specimen.

text: Two fossil specimens of Sclerothorax were discovered in the German state of

text: Hesse

text: in the 1920s. German paleontologist

text: Friedrich von Huene

text: studied the remains and named the new genus and species Sclerothorax hypselonotus in 1932. The

text: holotype

text: specimen preserved only the vertebral column, but was identifiable as a temnospondyl by its

text: rhachitomous

text: vertebrae and as a new species by its tall neural spines. Huene's second specimen included a complete skull,

text: pectoral girdle

text: , and back portion of the

text: dorsal vertebra

text: l column that was also clearly a temnospondyl. However, it was not apparent that the specimen belonged to the same species as the first until Huene exposed more of the crushed vertebrae and found that they were similar to those of his first specimen.

text: The visible part of the human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the nasal bones and the nasal cartilages, including the septal cartilage (which separates the nostrils) and the upper and lower lateral cartilages. On average the nose of a male is larger than that of a female.

text: The visible part of the human

text: nose

text: is the protruding part of the

text: face

text: that bears the

text: nostril

text: s. The shape of the nose is determined by the nasal bones and the nasal cartilages, including the septal cartilage (which separates the nostrils) and the upper and lower lateral cartilages. On average the nose of a

text: male

text: is larger than that of a

text: female

text: A large-scale screen of the Drosophila genome for mutants that exhibited axon guidance defects led to the discovery of the roundabout (robo) mutation. In robo mutants, axons were observed to inappropriately cross and recross the midline. It was subsequently found that the secreted protein Slit was the ligand for the Roundabout receptor. Vertebrate Slit proteins were identified shortly after, and were shown to bind both vertebrate and Drosophila Robo receptors and to mediate axonal repulsion of spinal cord explants. It was several more years before a functional analysis of the vertebrate Slit and Robo mutants was performed; this analysis demonstrated that Slit-Robo signaling regulates commissural axon guidance in vertebrates as well. Interestingly, while the vertebrate receptors Robo1 and Robo2 signal repulsion in response to Slit to prevent inappropriate midline crossing, a novel function for Robo3/Rig1 was discovered; unlike the other Robo receptors, it is required to promote midline crossing.

text: Bilaterians can be divided, based on events that occur very early in embryonic development, into two groups (superphyla) called protostomes and deuterostomes.  Deuterostomes include vertebrates as well as echinoderms, hemichordates (mainly acorn worms), and Xenoturbellidans. Protostomes, the more diverse group, include arthropods, molluscs, and numerous types of worms.  There is a basic difference between the two groups in the placement of the nervous system within the body:  protostomes possess a nerve cord on the ventral (usually bottom) side of the body, whereas in deuterostomes the nerve cord is on the dorsal (usually top) side.  In fact, numerous aspects of the body are inverted between the two groups, including the expression patterns of several genes that show dorsal-to-ventral gradients.  Most anatomists now consider that the bodies of protostomes and deuterostomes are "flipped over" with respect to each other, a hypothesis that was first proposed by Geoffroy Saint-Hilaire for insects in comparison to vertebrates.  Thus insects, for example, have nerve cords that run along the ventral midline of the body, while all vertebrates have spinal cords that run along the dorsal midline.

text: Bilaterians can be divided, based on events that occur very early in embryonic development, into two groups (

text: superphyla

text: ) called

text: protostomes

text: and

text: deuterostome

text: s.  Deuterostomes include vertebrates as well as

text: echinoderm

text: s,

text: hemichordates

text: (mainly acorn worms), and

text: Xenoturbellida

text: ns. Protostomes, the more diverse group, include

text: arthropod

text: s,

text: mollusc

text: s, and numerous types of worms.  There is a basic difference between the two groups in the placement of the nervous system within the body:  protostomes possess a nerve cord on the ventral (usually bottom) side of the body, whereas in deuterostomes the nerve cord is on the dorsal (usually top) side.  In fact, numerous aspects of the body are inverted between the two groups, including the expression patterns of several genes that show dorsal-to-ventral gradients.  Most anatomists now consider that the bodies of protostomes and deuterostomes are "flipped over" with respect to each other, a hypothesis that was first proposed by

text: Geoffroy Saint-Hilaire

text: for insects in comparison to vertebrates.  Thus insects, for example, have nerve cords that run along the ventral midline of the body, while all vertebrates have spinal cords that run along the dorsal midline.

text: The posterior inferior cerebellar artery (PICA), the largest branch of the vertebral artery, is one of the three main arterial blood supplies for the cerebellum, part of the brain. Occlusion of the posterior inferior cerebellar artery or one of its branches, or of the vertebral artery leads to lateral medullary syndrome also called Wallenberg syndrome.

text: The posterior inferior cerebellar artery (PICA), the largest branch of the

text: vertebral artery

text: , is one of the three main

text: arterial

text: blood

text: supplies for the

text: cerebellum

text: , part of the

text: brain

text: Occlusion

text: of the posterior inferior cerebellar artery or one of its branches, or of the vertebral artery leads to

text: lateral medullary syndrome

text: also called Wallenberg syndrome.

text: Not as arid as the tundra, the taiga is associated with the sub-Arctic regions of the Canadian Shield and is characterized by a greater number of both plant (600) and animal (206) species, many of which live there all year. The taiga covers about 20% of the total area of Quebec. The Canadian boreal forest is the northernmost and most abundant of the three forest areas in Quebec that straddle the Canadian Shield and the upper lowlands of the province. Given a warmer climate, the diversity of organisms is also higher, since there are about 850 plant species and 280 vertebrates species. The Canadian boreal forest covers 27% of the area of Quebec. The mixed forest is a transition zone between the Canadian boreal forest and deciduous forest. By virtue of its transient nature, this area contains a diversity of habitats resulting in large numbers of plant (1000) and vertebrates (350) species, despite relatively cool temperatures. The ecozone mixed forest covers 11.5% of the area of Quebec and is characteristic of the Laurentians, the Appalachians and the eastern lowlands forests. The third most northern forest area is characterized by deciduous forests. Because of its climate (average annual temperature of ), it is in this area that one finds the greatest diversity of species, including more than 1600 vascular plants and 440 vertebrates. Its relatively long growing season lasts almost 200 days and its fertile soils make it the centre of agricultural activity and therefore of urbanization of Quebec. Most of Quebec's population lives in this area of vegetation, almost entirely along the banks of the St. Lawrence. Deciduous forests cover approximately 6.6% of the area of Quebec.

text: Not as arid as the

text: tundra

text: , the

text: taiga

text: is associated with the sub-Arctic regions of the

text: Canadian Shield

text: and is characterized by a greater number of both plant (600) and animal (206) species, many of which live there all year. The

text: taiga

text: covers about 20% of the total area of Quebec. The

text: Canadian boreal forest

text: is the northernmost and most abundant of the three forest areas in Quebec that straddle the

text: Canadian Shield

text: and the upper

text: lowlands

text: of the province. Given a warmer climate, the diversity of organisms is also higher, since there are about 850 plant species and 280

text: vertebrate

text: s species. The

text: Canadian boreal forest

text: covers 27% of the area of Quebec. The

text: mixed forest

text: is a transition zone between the

text: Canadian boreal forest

text: and

text: deciduous forest

text: . By virtue of its transient nature, this area contains a diversity of habitats resulting in large numbers of plant (1000) and

text: vertebrate

text: s (350) species, despite relatively cool temperatures. The ecozone

text: mixed forest

text: covers 11.5% of the area of Quebec and is characteristic of the

text: Laurentians

text: , the

text: Appalachians

text: and the eastern

text: lowlands

text: forests. The third most northern forest area is characterized by

text: deciduous forest

text: s. Because of its climate (average annual temperature of ), it is in this area that one finds the greatest diversity of species, including more than 1600

text: vascular plants

text: and 440

text: vertebrate

text: s. Its relatively long growing season lasts almost 200 days and its fertile soils make it the centre of agricultural activity and therefore of urbanization of Quebec. Most of Quebec's population lives in this area of vegetation, almost entirely along the banks of the St. Lawrence. Deciduous forests cover approximately 6.6% of the area of Quebec.

text: The first tetrapods are four-legged, air-breathing, terrestrial animals from which the land vertebrates descended, including humans. They evolved from lobe-finned fish, appearing in coastal water in the middle Devonian, and giving rise to the first amphibians.

text: The first

text: tetrapods

text: are four-legged, air-breathing, terrestrial animals from which the land vertebrates descended, including humans. They evolved from

text: lobe-finned fish

text: , appearing in coastal water in the middle Devonian, and giving rise to the first

text: amphibians

text: To power the flippers, the shoulder girdle and the pelvis had been greatly modified, developing into broad bone plates at the underside of the body, which served as an attachment surface for large muscle groups, able to pull the limbs downwards. In the shoulder, the coracoid had become the largest element covering the major part of the breast. The scapula was much smaller, forming the outer front edge of the trunk. To the middle, it continued into a clavicle and finally a small interclavicular bone. As with most tetrapods, the shoulder joint was formed by the scapula and coracoid. In the pelvis, the bone plate was formed by the ischium at the rear and the larger pubic bone in front of it. The ilium, which in land vertebrates bears the weight of the hindlimb, had become a small element at the rear, no longer attached to either the pubic bone or the thighbone. The hip joint was formed by the ischium and the pubic bone. The pectoral and pelvic plates were connected by a plastron, a bone cage formed by the paired belly ribs that each had a middle and an outer section. This arrangement immobilised the entire trunk.

text: To power the flippers, the

text: shoulder girdle

text: and the

text: pelvis

text: had been greatly modified, developing into broad bone plates at the underside of the body, which served as an attachment surface for large muscle groups, able to pull the limbs downwards. In the shoulder, the

text: coracoid

text: had become the largest element covering the major part of the breast. The

text: scapula

text: was much smaller, forming the outer front edge of the trunk. To the middle, it continued into a

text: clavicle

text: and finally a small

text: interclavicular bone

text: . As with most

text: tetrapods

text: , the shoulder joint was formed by the scapula and coracoid. In the pelvis, the bone plate was formed by the

text: ischium

text: at the rear and the larger

text: pubic bone

text: in front of it. The

text: ilium

text: , which in land vertebrates bears the weight of the hindlimb, had become a small element at the rear, no longer attached to either the pubic bone or the thighbone. The hip joint was formed by the ischium and the pubic bone. The pectoral and pelvic plates were connected by a

text: plastron

text: , a bone cage formed by the paired

text: belly rib

text: s that each had a middle and an outer section. This arrangement immobilised the entire trunk.

text: An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.

text: An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an

text: animal

text: , composed of

text: mineralized tissue

text: Even many terrestrial vertebrates exhibit differences in the scaling of limb dimension, limb coordination and magnitude of forelimb-hind limb loading, in the dog, horse and elephant the structure of the distal forelimb is similar to that of the distal hind limb.  In the human, the structures of the hand are generally similar in shape and arrangement to those of the foot. Terrestrial vertebrate quadrupeds and bipeds generally possess distal limb and foot endoskeleton structures that are aligned in series, stacked in a relatively vertical orientation and arranged in a quasi-columnar fashion in the extended limb.  In the dog and horse, the bones of the proximal limbs are oriented vertically, whereas the distal limb structures of the ankle and foot have an angulated orientation.  In humans and elephants, a vertical-column orientation of the bones in the limbs and feet is also evident for associated skeletal muscle-tendon units.  The horse’s foot contains an external nail (hoof) oriented about the perimeter in the shape of a semicircle.  The underlying bones are arranged in a semi-vertical orientation.  The dog’s paw similarly contains bones arranged in a semi-vertical orientation.

text: Even many terrestrial vertebrates exhibit differences in the scaling of limb dimension, limb coordination and magnitude of forelimb-hind limb loading, in the dog, horse and elephant the structure of the distal forelimb is similar to that of the distal hind limb.  In the human, the structures of the hand are generally similar in shape and arrangement to those of the foot. Terrestrial vertebrate quadrupeds and bipeds generally possess distal limb and foot

text: endoskeleton

text: structures that are aligned in series, stacked in a relatively vertical orientation and arranged in a quasi-columnar fashion in the extended limb.  In the dog and horse, the bones of the proximal limbs are oriented vertically, whereas the distal limb structures of the ankle and foot have an angulated orientation.  In humans and elephants, a vertical-column orientation of the bones in the limbs and feet is also evident for associated skeletal muscle-tendon units.  The horse’s foot contains an external nail (hoof) oriented about the perimeter in the shape of a semicircle.  The underlying bones are arranged in a semi-vertical orientation.  The dog’s paw similarly contains bones arranged in a semi-vertical orientation.

text: In 1969, Dr. Opdyke & Ken Henry used marine core data for a convincing test of the GADhypothesis that is central to the use of paleomagnetism in continentalreconstruction. Opdyke’s work with Nick Shackleton in 1973 marked thebeginning of the integration of oxygen isotope stratigraphy andmagnetostratigraphy that has led to current methods of tuningtimescales. Neil pioneered magnetic stratigraphy in terrestrial(non-marine) sediments and produced some of the most impressive records, notably from Pakistan and southwestern USA. These studies led to a vastly improved time frame for vertebrate evolution and allowed the documentation of mammal migration.

text: In 1969, Dr. Opdyke & Ken Henry used marine core data for a convincing test of the GADhypothesis that is central to the use of paleomagnetism in continentalreconstruction. Opdyke’s work with

text: Nick Shackleton

text: in 1973 marked thebeginning of the integration of oxygen isotope stratigraphy andmagnetostratigraphy that has led to current methods of tuningtimescales. Neil pioneered magnetic stratigraphy in terrestrial(non-marine) sediments and produced some of the most impressive records, notably from Pakistan and southwestern USA. These studies led to a vastly improved time frame for vertebrate evolution and allowed the documentation of mammal migration.

text: The fauna of the region is rich in species, many of them endemic and represented only by small populations which indicates a fragile ecosystem. Birds are the most numerous group of vertebrates, with 58 species in 50 different genus and 22 families. Hunting, deforestation, the introduction of agriculture and domestic animals have limited the number of species and number of individuals per species. Mammals found in the area include the tapeti, jaguarundi, crab-eating fox, and common opossum.

text: The fauna of the region is rich in species, many of them endemic and represented only by small populations which indicates a fragile ecosystem. Birds are the most numerous group of vertebrates, with 58 species in 50 different genus and 22 families. Hunting,

text: deforestation

text: , the introduction of agriculture and domestic animals have limited the number of species and number of individuals per species. Mammals found in the area include the

text: tapeti

text: jaguarundi

text: crab-eating fox

text: , and

text: common opossum

text: Vertebrate palaeontology had mapped out the evolutionary sequence of vertebrates as currently understood fairly well by the closing of the 19th century, followed by a reasonable understanding of the evolutionary sequence of the plant kingdom by the early 20th century. The tying together of the various trees into a grand Tree of Life only really became possible with advancements in microbiology and biochemistry in the period between the World Wars.

text: Vertebrate palaeontology

text: had mapped out the evolutionary sequence of vertebrates as currently understood fairly well by the closing of the 19th century, followed by a reasonable understanding of the evolutionary sequence of the

text: plant kingdom

text: by the early 20th century. The tying together of the various trees into a grand Tree of Life only really became possible with advancements in

text: microbiology

text: and

text: biochemistry

text: in the period between the World Wars.

text: Bone tissue is a mineralized connective tissue. It is formed by cells, called osteoblasts, that deposit a matrix of Type-I collagen and also release calcium, magnesium, and phosphate ions that ultimately combine chemically within the collagenous matrix into a crystalline mineral, known as bone mineral, in the form of carbonated hydroxyapatite. The combination of hard mineral and flexible collagen makes bone harder and stronger than cartilage without being brittle. Cortical bone consists of a repeating structure called an osteon or haversian system, which is the primary anatomical and functional unit. Each osteon has concentric lamellae (layers) of mineralized matrix, which are deposited around a central canal, known as the haversian canal, each containing blood and nerve supply.

text: Bone tissue is a

text: mineralized connective tissue

text: . It is formed by cells, called

text: osteoblast

text: s, that deposit a matrix of

text: Type-I collagen

text: and also release calcium, magnesium, and phosphate ions that ultimately combine chemically within the collagenous matrix into a crystalline mineral, known as

text: bone mineral

text: , in the form of carbonated

text: hydroxyapatite

text: . The combination of hard mineral and flexible collagen makes bone harder and stronger than

text: cartilage

text: without being brittle. Cortical bone consists of a repeating structure called an

text: osteon

text: or haversian system, which is the primary anatomical and functional unit. Each osteon has concentric

text: lamellae

text: (layers) of mineralized matrix, which are deposited around a central canal, known as the

text: haversian canal

text: , each containing blood and nerve supply.

text: Controversy about the 2R hypothesis hinged on the nature of paralogy regions. It is not disputed that human chromosomes bear sets of genes related to sets of genes on other chromosomes; the controversy centres on whether they were generated by large-scale duplications that doubled all the genes at the same time, or whether a series of individual gene duplications occurred followed by chromosomal rearrangement to shuffle sets of genes together. Hughes and colleagues found that phylogenetic trees built from different gene families within paralogy regions had different shapes, suggesting that the gene families had different evolutionary histories. This was suggested to be inconsistent with the 2R hypothesis. However, other researchers have argued that such 'topology tests' do not test 2R rigorously, because recombination could have occurred between the closely related chromosomes generated by polyploidy, because inappropriate genes had been compared and because different predictions are made if genome duplication occurred through hybridisation between species. In addition, several researchers were able to date duplications of gene families within paralogy regions consistently to the early evolution of vertebrates, after divergence from amphioxus, consistent with the 2R hypothesis. When complete genome sequences became available for vertebrates, Ciona intestinalis and amphioxus, it was found that much of the human genome was arranged in paralogy regions that could be traced to large-scale duplications, and that these duplications occurred after vertebrates had diverged from tunicates  and amphioxus. This would date the two genome duplications to between 550 and 450 million years ago.

text: Controversy about the 2R hypothesis hinged on the nature of

text: paralogy regions

text: . It is not disputed that human

text: chromosomes

text: bear sets of genes related to sets of genes on other

text: chromosomes

text: ; the controversy centres on whether they were generated by large-scale duplications that doubled all the genes at the same time, or whether a series of individual

text: gene duplications

text: occurred followed by

text: chromosomal rearrangement

text: to shuffle sets of genes together. Hughes and colleagues found that

text: phylogenetic trees

text: built from different

text: gene families

text: within

text: paralogy regions

text: had different shapes, suggesting that the gene families had different evolutionary histories. This was suggested to be inconsistent with the 2R hypothesis. However, other researchers have argued that such 'topology tests' do not test 2R rigorously, because

text: recombination

text: could have occurred between the closely related chromosomes generated by

text: polyploidy

text: , because inappropriate genes had been compared and because different predictions are made if

text: genome duplication

text: occurred through

text: hybrid

text: isation between species. In addition, several researchers were able to date duplications of gene families within

text: paralogy regions

text: consistently to the early evolution of vertebrates, after divergence from amphioxus, consistent with the 2R hypothesis. When complete

text: genome sequences

text: became available for

text: vertebrates

text: Ciona intestinalis

text: and

text: amphioxus

text: , it was found that much of the

text: human genome

text: was arranged in

text: paralogy regions

text: that could be traced to large-scale duplications, and that these duplications occurred after

text: vertebrates

text: had diverged from

text: tunicates

text: and

text: amphioxus

text: . This would date the two

text: genome duplications

text: to between 550 and 450 million years ago.

text: Surgical treatmentIn some cases, surgery is the only way to eliminate or reduce pain. There are several types of surgery for treatment of hallux rigidus. The type of surgery is based on the stage of hallux rigidus.  Stage 1 hallux rigidus involves some loss of range of motion of the big toe joint or first MTP joint and is often treated conservatively with prescription foot orthotics.  Stage 2 hallux rigidus involves greater loss of range of motion and cartilage and may be treated via cheilectomy in which the metatarsal head is reshaped and bone spurs reduced.  Stage 3 hallux rigidus often involves significant cartilage loss and may be treated by an osteotomy in which cartilage on the first metatarsal head is repositioned, possibly coupled with a hemi-implant in which the base of the proximal phalanx (base of the big toe) is resurfaced.  Stage 4 hallux rigidus, also known as end stage hallux rigidus involves severe loss of range of motion of the big toe joint and cartilage loss.  Stage 4 hallux rigidus may be treated via fusion of the joint (arthrodesis) or implant arthroplasty in which both sides of the joint are resurfaced or a hinged implant is used.  Fusion of the joint is often viewed as more definitive but may lead to significant alteration of gait causing postural symptomatology. The implants termed "two part unconstrained" implants in which a "ball" type device is placed on the first metatarsal head and "socket" portion on the base of the big toe do not have a good long term track record.  The hinged implants have been in existence since the 1970s, have been continually improved and have the best record of improving long term function.

text: Surgical treatmentIn some cases, surgery is the only way to eliminate or reduce pain. There are several types of surgery for treatment of hallux rigidus. The type of surgery is based on the stage of hallux rigidus.  Stage 1 hallux rigidus involves some loss of range of motion of the big toe joint or first MTP joint and is often treated conservatively with prescription foot orthotics.  Stage 2 hallux rigidus involves greater loss of range of motion and cartilage and may be treated via

text: cheilectomy

text: in which the metatarsal head is reshaped and bone spurs reduced.  Stage 3 hallux rigidus often involves significant cartilage loss and may be treated by an osteotomy in which cartilage on the first metatarsal head is repositioned, possibly coupled with a hemi-implant in which the base of the proximal phalanx (base of the big toe) is resurfaced.  Stage 4 hallux rigidus, also known as end stage hallux rigidus involves severe loss of range of motion of the big toe joint and cartilage loss.  Stage 4 hallux rigidus may be treated via fusion of the joint (

text: arthrodesis

text: ) or implant

text: arthroplasty

text: in which both sides of the joint are resurfaced or a hinged implant is used.  Fusion of the joint is often viewed as more definitive but may lead to significant alteration of gait causing postural symptomatology. The implants termed "two part unconstrained" implants in which a "ball" type device is placed on the first metatarsal head and "socket" portion on the base of the big toe do not have a good long term track record.  The hinged implants have been in existence since the 1970s, have been continually improved and have the best record of improving long term function.

text: It is a common misconception that common snapping turtles may be safely picked up by the tail with no harm to the animal; in fact, this has a high chance of injuring the turtle, especially the tail itself and the vertebral column. Lifting the turtle with the hands is difficult and dangerous. Snappers can stretch their necks back across their own carapace and to their hind feet on either side to bite. When they feel stressed, they release a musky odor from behind their legs.

text: It is a common misconception that common snapping turtles may be safely picked up by the tail with no harm to the animal; in fact, this has a high chance of injuring the turtle, especially the tail itself and the

text: vertebra

text: l column. Lifting the turtle with the hands is difficult and dangerous. Snappers can stretch their necks back across their own carapace and to their hind feet on either side to bite. When they feel stressed, they release a musky odor from behind their legs.

text: Intramembranous ossification is one of the two essential processes during fetal development of the gnathostome (excluding chondrichthyans such as sharks) skeletal system by which rudimentary bone tissue is created. Intramembranous ossification is also an essential process during the natural healing of bone fractures and the rudimentary formation of bones of the head. Unlike endochondral ossification, which is the other process by which bone tissue is created during fetal development, cartilage is not present during intramembranous ossification.

text: Intramembranous ossification is one of the two essential processes during

text: fetal

text: development of the

text: gnathostome

text: (excluding

text: chondrichthyans

text: such as

text: shark

text: s)

text: skeletal system

text: by which rudimentary

text: bone tissue

text: is created. Intramembranous ossification is also an essential process during the natural healing of

text: bone fractures

text: and the rudimentary formation of

text: bone

text: s of the

text: head

text: . Unlike

text: endochondral ossification

text: , which is the other process by which bone tissue is created during fetal development,

text: cartilage

text: is not present during intramembranous ossification.

text: Oikopleura dioica is used as a model organism, a role for which it has several features to recommend it. It has the typical chordate body plan, it is simple to keep and breed in the laboratory, it produces large numbers of eggs and the generation time is only four days at . In the Sars International Centre for Marine Molecular Biology, inbred lines have been developed using repeated matings of closely related individuals. The molecular base of a number of aspects of vertebrate development is identical in these simple chordates to those in higher vertebrates. As an example, the brachyury gene and the homolog of the PAX2 gene both play a similar role in the development of tunicates as they do in vertebrates. Complex aspects of vertebral development such as the differentiation of the central nervous system can thus be studied in the laboratory. The genome has been sequenced and contains about 15,000 genes, approximately half the number occurring in vertebrates. Comparison of the genome with that of other chordates will help identify the genes which appeared early in the vertebrate lineage.

text: Oikopleura dioica is used as a

text: model organism

text: , a role for which it has several features to recommend it. It has the typical chordate body plan, it is simple to keep and breed in the laboratory, it produces large numbers of eggs and the generation time is only four days at . In the

entity_name: Sars International Centre for Marine Molecular Biology

text: Sars International Centre for Marine Molecular Biology

text: , inbred lines have been developed using repeated matings of closely related individuals. The molecular base of a number of aspects of vertebrate development is identical in these simple chordates to those in higher vertebrates. As an example, the

text: brachyury

text: gene and the

text: homolog

text: of the

text: gene both play a similar role in the development of tunicates as they do in vertebrates. Complex aspects of vertebral development such as the differentiation of the

text: central nervous system

text: can thus be studied in the laboratory. The genome has been sequenced and contains about 15,000 genes, approximately half the number occurring in vertebrates. Comparison of the genome with that of other chordates will help identify the genes which appeared early in the vertebrate lineage.

text: Like all Plasmodium species P. lutzi has both vertebrate and insect hosts. The vertebrate hosts for this parasite are birds.

text: Like all Plasmodium species P. lutzi has both

text: vertebrate

text: and

text: insect

text: bird

text: s.

text: In the species that have cartilage in the sublingua or lytta, that cartilage is not derived from the hyoid bone or hyoid arch (the bone and cartilage that supports the tongue). Instead, the cartilage of the sublingua is a separately developed structure specifically adapted to support the sublingua.

text: In the species that have cartilage in the sublingua or lytta, that cartilage is not derived from the

text: hyoid bone

text: or

text: hyoid arch

text: (the bone and cartilage that supports the tongue). Instead, the cartilage of the sublingua is a separately developed structure specifically adapted to support the sublingua.

text: In many vertebrates, the sclera is reinforced with plates of cartilage or bone, together forming a circular structure called the sclerotic ring. In primitive fish, this ring consists of four plates, but the number is lower in many living ray-finned fishes, and much higher in lobe-finned fishes, various reptiles, and birds. The ring has disappeared in many groups, including living amphibians, some reptiles and fish, and all mammals.

text: In many

text: vertebrate

text: s, the sclera is reinforced with plates of

text: cartilage

text: or

text: bone

text: , together forming a circular structure called the

text: sclerotic ring

text: . In primitive fish, this ring consists of four plates, but the number is lower in many living

text: ray-finned fish

text: es, and much higher in

text: lobe-finned fish

text: es, various

text: reptile

text: s, and

text: bird

text: s. The ring has disappeared in many groups, including living

text: amphibian

text: s, some reptiles and fish, and all

text: mammal

text: s.

text: The sequestration of oxygen-carrying proteins inside specialized cells (as opposed to oxygen carriers being dissolved in body fluid) was an important step in the evolution of vertebrates as it allows for less viscous blood, higher concentrations of oxygen, and better diffusion of oxygen from the blood to the tissues. The size of erythrocytes varies widely among vertebrate species; erythrocyte width is on average about 25% larger than capillary diameter, and it has been hypothesized that this improves the oxygen transfer from erythrocytes to tissues.

text: The sequestration of oxygen-carrying proteins inside specialized cells (as opposed to oxygen carriers being dissolved in body fluid) was an important step in the evolution of

text: vertebrates

text: as it allows for less

text: viscous

text: blood, higher concentrations of oxygen, and better diffusion of oxygen from the blood to the tissues. The size of erythrocytes varies widely among vertebrate species; erythrocyte width is on average about 25% larger than

text: capillary

text: diameter, and it has been hypothesized that this improves the oxygen transfer from erythrocytes to tissues.

text: Landscape can have an influence on how communities and societies evolve and vice verse. Communities can shape how the landscape is used based on the needs of the community. We can see an example of this in Canada's landscape and the role the railroads had in shaping the community. With the introduction of the railroad, Canada's wild lands were more susceptible to exploitation. On the contrary to that, the railroad system also allowed the community to experience Canada's array of National Parks.(2)

text: The general structure of human vertebrae is fairly typical of that found in mammals, reptiles, and birds. The shape of the vertebral body does, however, vary somewhat between different groups. In mammals, such as humans, it typically has flat upper and lower surfaces, while in reptiles the anterior surface commonly has a concave socket into which the expanded convex face of the next vertebral body fits. Even these patterns are only generalisations, however, and there may be variation in form of the vertebrae along the length of the spine even within a single species. Some unusual variations include the saddle-shaped sockets between the cervical vertebrae of birds and the presence of a narrow hollow canal running down the centre of the vertebral bodies of geckos and tuataras, containing a remnant of the notochord.

text: The general structure of human vertebrae is fairly typical of that found in

text: mammal

text: s,

text: reptile

text: s, and

text: bird

text: s. The shape of the vertebral body does, however, vary somewhat between different groups. In mammals, such as humans, it typically has flat upper and lower surfaces, while in reptiles the anterior surface commonly has a concave socket into which the expanded convex face of the next vertebral body fits. Even these patterns are only generalisations, however, and there may be variation in form of the vertebrae along the length of the spine even within a single species. Some unusual variations include the saddle-shaped sockets between the cervical vertebrae of birds and the presence of a narrow hollow canal running down the centre of the vertebral bodies of

text: gecko

text: s and

text: tuatara

text: s, containing a remnant of the notochord.

text: In vertebrates a rachis can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the rachis usually forms the supporting axis of the body and is then called the spine or vertebral column.  Rachis can also mean the central shaft of pennaceous feathers.

text: In

text: vertebrate

text: s a rachis can refer to the series of articulated

text: vertebrae

text: , which encase the

text: spinal cord

text: . In this case the rachis usually forms the supporting axis of the body and is then called the

text: spine

text: or

text: vertebral column

text: .  Rachis can also mean the central shaft of

text: pennaceous feather

text: s.

text: The redescription of 2012 established two autapomorphies, unique derived traits: the presence of chevrons at the tail base that were four times as long as the vertebral centra; and the possession at the tail base vertebrae of front joint processes, prezygapophyses, the inner bases of which formed a bowl-shaped depression that extended upwards into a deep trough on the front surface of the spine.

text: The redescription of 2012 established two

text: autapomorphies

text: , unique derived traits: the presence of chevrons at the tail base that were four times as long as the vertebral centra; and the possession at the tail base vertebrae of front joint processes,

text: prezygapophyses

text: , the inner bases of which formed a bowl-shaped depression that extended upwards into a deep trough on the front surface of the spine.

text: The museum became a center of authority for the study of vertebrate biology and evolution on the West Coast, comparable to other major natural history museums in the United States.

text: The museum became a center of authority for the study of

text: vertebrate

text: biology

text: and

text: evolution

text: on the West Coast, comparable to other major natural history museums in the United States.

text: The spiracle is a small hole behind each eye that opens to the mouth in some fish. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar to the other gill opening.  With the evolution of the jaw in the early jawed vertebrates, this gill slit was "caught" between the forward gill-rod (now functioning as the jaw) and the next rod, the hyomandibular bone, supporting the jaw hinge and anchoring the jaw to the skull proper. The gill opening was closed off from below, the remaining opening was small and hole-like, and is termed a "spiracle". The spiracle is still found in all cartilaginous fish except requiem sharks, hammerhead sharks, and chimaeras, and is found in some primitive bony fishes, the (coelacanth, sturgeon, paddlefish and bichirs). It is also seen as an otic notch in the skull of the extinct  labyrinthodonts, and is thought to be associated with the ear opening in amniotes and frogs.

text: The spiracle is a small hole behind each eye that opens to the mouth in some

text: fish

text: . In the primitive

text: jawless fish

text: the first gill opening immediately behind the mouth is essentially similar to the other gill opening.  With the

text: evolution

text: of the

text: jaw

text: in the early

text: jawed vertebrates

text: , this gill slit was "caught" between the forward gill-rod (now functioning as the jaw) and the next rod, the

text: hyomandibular bone

text: , supporting the jaw hinge and anchoring the jaw to the

text: skull

text: proper. The gill opening was closed off from below, the remaining opening was small and hole-like, and is termed a "spiracle". The spiracle is still found in all

text: cartilaginous fish

text: except

text: requiem shark

text: s,

text: hammerhead shark

text: s, and

text: chimaera

text: s, and is found in some primitive

text: bony fishes

text: , the (

text: coelacanth

text: sturgeon

text: paddlefish

text: and

text: bichir

text: s). It is also seen as an

text: otic notch

text: in the skull of the extinct

text: labyrinthodonts

text: , and is thought to be associated with the

text: ear

text: opening in

text: amniote

text: s and

text: frog

text: s.

text: Comprehensive sequence searches across multiple taxonomic groups have failed to identify MHC and TCRs outside of the jawed vertebrates. Allorecognition in these animals rely on molecular mechanisms distinct from those of the jawed vertebrates. In sponges, various receptors (sponge adhesion molecules, receptor tyrosine kinase) with domains similar to those found in immunoglobulins have been identified. Interestingly, sequence variability in "hot spots" have been identified in these receptors. It would appear that molecules which, later in evolution, were exploited in the adaptive immune response, had an earlier role in innate recognition. Lampreys and hagfish appear to have evolved, by convergent evolution, an adaptive immune response that is independent and distinct from the adaptive immune systems of higher vertebrates. Lymphocyte-like cells in these fish express highly variable lymphocyte receptor genes, which undergo somatic rearrangements reminiscent of the manner in which mammalian immunoglobulin genes are rearranged during development.

text: Comprehensive sequence searches across multiple taxonomic groups have failed to identify MHC and TCRs outside of the jawed vertebrates. Allorecognition in these animals rely on molecular mechanisms distinct from those of the jawed vertebrates. In sponges, various receptors (sponge adhesion molecules, receptor tyrosine kinase) with domains similar to those found in

text: immunoglobulins

text: have been identified. Interestingly, sequence variability in "hot spots" have been identified in these receptors. It would appear that molecules which, later in evolution, were exploited in the adaptive immune response, had an earlier role in innate recognition. Lampreys and hagfish appear to have evolved, by

text: convergent evolution

text: , an adaptive immune response that is independent and distinct from the adaptive immune systems of higher vertebrates.

text: Lymphocyte

text: -like cells in these fish express highly variable lymphocyte receptor genes, which undergo somatic rearrangements reminiscent of the manner in which mammalian immunoglobulin genes are rearranged during development.

text: However, a few vertebrates have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon and Latimeria. Jawed vertebrates are typified by paired appendages (fins or legs, which may be secondarily lost), but this is not part of the definition of vertebrates as a whole.

text: However, a few vertebrates have secondarily lost this anatomy, retaining the notochord into adulthood, such as the

text: sturgeon

text: and

text: Latimeria

text: Jawed vertebrates

text: are typified by paired appendages (fins or legs, which may be secondarily lost), but this is not part of the definition of vertebrates as a whole.

text: Chondrichthyes (; from Greek χονδρ- chondr- 'cartilage', ἰχθύς ichthys 'fish') is a class that contains the cartilaginous fishes: they are jawed vertebrates with paired fins, paired nares, scales, a heart with its chambers in series, and skeletons made of cartilage rather than bone. The class is divided into two subclasses: Elasmobranchii (sharks, rays, skates, and sawfish) and Holocephali (chimaeras, sometimes called ghost sharks, which are sometimes separated into their own class).

text: Chondrichthyes (; from Greek χονδρ- chondr- 'cartilage', ἰχθύς ichthys 'fish') is a

text: class

text: that contains the cartilaginous fishes: they are jawed

text: vertebrates

text: with paired fins, paired

text: nare

text: s, scales, a heart with its chambers in series, and skeletons made of

text: cartilage

text: rather than

text: bone

text: . The class is divided into two subclasses:

text: Elasmobranchii

text: shark

text: s,

text: ray

text: s,

text: skate

text: s, and

text: sawfish

text: ) and

text: Holocephali

text: chimaera

text: s, sometimes called ghost sharks, which are sometimes separated into their own class).

text: Examples in animals are more common in non-vertebrates such as flatworms, leeches, and brine shrimp. Within vertebrates, examples of stable polyploidy include the salmonids and many cyprinids (i.e. carp). Some fish have as many as 400 chromosomes. Polyploidy also occurs commonly in amphibians; for example the biomedically-important Xenopus genus contains many different species with as many as 12 sets of chromosomes (dodecaploid). Polyploid lizards are also quite common, but are sterile and must reproduce by parthenogenesis. Polyploid mole salamanders (mostly triploids) are all female and reproduce by kleptogenesis, "stealing" spermatophores from diploid males of related species to trigger egg development but not incorporating the males' DNA into the offspring. While mammalian liver cells are polyploid, rare instances of polyploid mammals are known, but most often result in prenatal death.

text: Examples in animals are more common in non-vertebrates such as

text: flatworm

text: s,

text: leech

text: es, and

text: brine shrimp

text: . Within vertebrates, examples of stable polyploidy include the

text: salmonids

text: and many

text: cyprinids

text: (i.e.

text: carp

text: ). Some fish have as many as 400 chromosomes. Polyploidy also occurs commonly in amphibians; for example the biomedically-important

text: Xenopus

text: genus contains many different species with as many as 12 sets of chromosomes (dodecaploid). Polyploid lizards are also quite common, but are sterile and must reproduce by

text: parthenogenesis

text: . Polyploid

text: mole salamanders

text: (mostly triploids) are all female and reproduce by

text: kleptogenesis

text: , "stealing"

text: spermatophore

text: s from diploid males of related species to trigger egg development but not incorporating the males' DNA into the offspring. While mammalian liver cells are polyploid, rare instances of polyploid

text: mammals

text: are known, but most often result in

text: prenatal

text: death.

text: Animals also engage in kleptothermy in which they share or even steal each other's body warmth. In endotherms such as bats and birds (such as the mousebird and emperor penguin) it allows the sharing of body heat (particularly amongst juveniles). This allows the individuals to increase their thermal inertia (as with gigantothermy) and so reduce heat loss. Some ectotherms share burrows of ectotherms. Other animals exploit termite mounds.

text: Animals also engage in

text: kleptothermy

text: in which they share or even steal each other's body warmth. In endotherms such as

text: bat

text: s and birds (such as the

text: mousebird

text: and

text: emperor penguin

text: ) it allows the sharing of body heat (particularly amongst juveniles). This allows the individuals to increase their

text: thermal inertia

text: (as with

text: gigantothermy

text: ) and so reduce

text: heat

text: loss. Some ectotherms share burrows of ectotherms. Other animals exploit

text: termite

text: mounds.

text: Dr. Stallsmith consistently teaches Introduction Biology, Organismal Biology, Vertebrate Zoology, and Vertebrate Reproduction at UAH, where he is very popular with his students.

text: In the study of conditioned reflexes by the method of free movements, Beritashvili was confronted with actions that could not be explained by or described as conditioned reflexes. For instance, if the animal only once found food at a given place, on that and following days it ran to the same place. Beritashvili concluded that in higher vertebrates an image of the food and its location arose during the animal’s perception of the food. This image was reproduced when the animal was in the same situation; moreover the animal later behaved in the same manner by sniffing, etc., if it returned to the place where it had first found the food. This orientating, or investigatory image-guided behavior, supposed the projection of the image of the object the animal recognized onto the outer environment where it had first perceived the food. Such image-regulated behavior was termed by Beritashvili psychoneural, or later image-driven behavior. He assumed this behavior to be a complex of voluntary movements peculiar to higher vertebrates and mammals as well as to little children. He supposed that whenever a feeding behavior is learned that is directed towards a particular food box, it originally conforms to the reproduced food image. The image of the food box’s location is also reproduced and can play an accessory role. Thus, Beritashvili straightforwardly called the total feeding behavior of an animal “image-driven”, in case its movements during the task were unrestrained. While such descriptive terminology carries some prejudice from the days of behaviorism as being hopelessly anthropomorphic, denying the validity of the term is equally suspect. Given the manifold similarities not only in the anatomy, but also in the psychophysics of many lower primates and man, it is strange to deny that equivalent anatomy and physiology generate similar percepts. Human “image-driven” behavior is itself a sufficiently general experience so that a diminished form thereof seems defensibly lucid in describing the equivalent phenomenon among mammals.

text: The Meckelian Cartilage, also known as "Meckel's Cartilage", is a piece of cartilage from which the mandibles (lower jaws) of vertebrates evolved. Originally it was the lower of two cartilages which supported the first branchial arch in early fish. Then it grew longer and stronger, and acquired muscles capable of closing the developing jaw.

text: The Meckelian Cartilage, also known as "Meckel's Cartilage", is a piece of

text: cartilage

text: from which the mandibles (lower jaws) of

text: vertebrates

text: evolved. Originally it was the lower of two cartilages which supported the first

text: branchial arch

text: in early

text: fish

text: . Then it grew longer and stronger, and acquired muscles capable of closing the developing jaw.

text: Like all Plasmodium species P. papernai has both vertebrate and insect hosts. The vertebrate hosts for this parasite are birds.

text: Like all Plasmodium species P. papernai has both

text: vertebrate

text: and

text: insect

text: bird

text: s.

text: Disagreement on whether the evolution of the camera eye within cephalopods and within vertebrates is a parallel evolution or a convergent evolution still exists, although is mostly resolved. The current standing is that of a convergent evolution for their analogous camera-type eye.

text: Disagreement on whether the evolution of the camera eye within cephalopods and within vertebrates is a

text: parallel evolution

text: or a

text: convergent evolution

text: still exists, although is mostly resolved. The current standing is that of a convergent evolution for their analogous camera-type eye.

text: The vertebral column consists of an atlas (composed of two vertebrae) without ribs; numerous precaudal vertebrae, all of which, except the first or first three, bear long, movable, curved ribs with a small posterior tubercle at the base, the last of these ribs sometimes forked; two to ten so-called lumbar vertebrae without ribs, but with bifurcate transverse processes (lymphapophyses) enclosing the lymphatic vessels; and a number of ribless caudal vertebrae with simple transverse processes. When bifid, the ribs or transverse processes have the branches regularly superposed.

text: The

text: vertebral column

text: consists of an

text: atlas

text: (composed of two vertebrae) without

text: rib

text: s; numerous

text: precaudal vertebrae

text: , all of which, except the first or first three, bear long, movable, curved ribs with a small posterior

text: tubercle

text: at the base, the last of these ribs sometimes forked; two to ten so-called

text: lumbar vertebrae

text: without ribs, but with bifurcate

text: transverse processes

text: (lymphapophyses) enclosing the

text: lymphatic vessel

text: s; and a number of ribless

text: caudal vertebrae

text: with simple transverse processes. When

text: bifid

text: , the ribs or transverse processes have the branches regularly superposed.

text: The skeleton of the lungfish is partly bone, and partly cartilage. The vertebrae are pure cartilage, while the ribs are hollow tubes filled with a cartilaginous substance. The body of the lungfish is covered with large, bony scales. Ten rows occur on each side, grading to small scales on the fins. The scales are each embedded in their own pockets, and overlap extensively, such that vulnerable areas of the body are covered by a thickness of at least four scales. Two unusually large and thick interlocking scales cover the back of the head where the bony skull is thin. They have powerful diphycercal tails that are long and paddle-shaped. The pectoral fins are large, fleshy, and flipper-like. The pelvic fins are also fleshy and flipper-like and situated well back on the body. The dorsal fin commences in the middle of the back and is confluent with the caudal and anal fins.

text: The skeleton of the lungfish is partly bone, and partly

text: cartilage

text: . The vertebrae are pure cartilage, while the ribs are hollow tubes filled with a cartilaginous substance. The body of the lungfish is covered with large, bony scales. Ten rows occur on each side, grading to small scales on the fins. The scales are each embedded in their own pockets, and overlap extensively, such that vulnerable areas of the body are covered by a thickness of at least four scales. Two unusually large and thick interlocking scales cover the back of the head where the bony skull is thin. They have powerful

text: diphycercal

text: tails that are long and paddle-shaped. The

text: pectoral fin

text: s are large, fleshy, and flipper-like. The

text: pelvic fin

text: s are also fleshy and flipper-like and situated well back on the body. The

text: dorsal fin

text: commences in the middle of the back and is confluent with the

text: caudal

text: and

text: anal fin

text: s.

text: The describing authors determined some distinguishing characteristics. The last dorsal vertebra has a pleurocoel, or pneumatic cavity, that is bounded by an enlarged posterior ridge between the diapophysis and the vertebral body, by the posterior ridge between the parapophysis and the vertebral body; and by the vertebral body itself. The rear dorsal vertebra has a well-developed horizontal ridge between the prezygapophysis and the parapophysis. The last dorsal vertebra has a parapophysis that protrudes more laterally than the diapophysis. The groove in the underside of the rear blade of the ilium, serving as an attachment to the musculus caudofemoralis brevis, is shallow and the "brevis shelf", the inner surface of the medial blade wall uncovered by it, is short and shaped like a ridge. The pubic peduncle of the ilium, to which the pubic bone is attached, at the rear side transversely expands to below.

text: The describing authors determined some distinguishing characteristics. The last dorsal vertebra has a pleurocoel, or pneumatic cavity, that is bounded by an enlarged posterior ridge between the

text: diapophysis

text: and the vertebral body, by the posterior ridge between the

text: parapophysis

text: and the vertebral body; and by the vertebral body itself. The rear dorsal vertebra has a well-developed horizontal ridge between the

text: prezygapophysis

text: and the parapophysis. The last dorsal vertebra has a parapophysis that protrudes more laterally than the diapophysis. The groove in the underside of the rear blade of the ilium, serving as an attachment to the

text: musculus caudofemoralis brevis

text: , is shallow and the "brevis shelf", the inner surface of the medial blade wall uncovered by it, is short and shaped like a ridge. The pubic peduncle of the ilium, to which the pubic bone is attached, at the rear side transversely expands to below.

text: with cartilaginous discs between each vertebral body. The spinal cord sits within the cervical part of the vertebral column. The spinal column carries nerves that carry sensory and motor information from the brain down to the rest of the body. From top to bottom the cervical spine is gently curved in convex-forward fashion.

text: with

text: cartilaginous discs

text: between each vertebral body. The spinal cord sits within the cervical part of the vertebral column. The spinal column carries nerves that carry sensory and motor information from the

text: brain

text: down to the rest of the body. From top to bottom the cervical spine is gently curved in convex-forward fashion.

text: Placement of this group among the jawless vertebrates is a matter of dispute. While today enough fossil diversity is known to make a close relationship among the "ostracoderms" unlikely, this has muddied the issue of the Hyperoartia's closest relatives. Traditionally the group was placed in a superclass Cyclostomata together with the Myxini (hagfishes). More recently, it has been proposed that the Myxini are more basal among the skull-bearing chordates, while the Hyperoartia are retained among vertebrates. But even though this may be correct, the lampreys represent one of the oldest divergences of the vertebrate lineage, and whether they are better united with some "ostracoderms" in the Cephalaspidomorphi, or not closer to these than to e.g. to other "ostracoderms" of the Pteraspidomorphi, or even the long-extinct conodonts, is still to be resolved. Even the very existence of the class Hyperoartia is disputed, with some analyses favoring a treatment of the "basal Hyperoartia" as a monophyletic lineage Jamoytiiformes that may in fact be very close to the ancestral jawed vertebrates.

text: Placement of this group among the

text: jawless vertebrates

text: is a matter of dispute. While today enough fossil diversity is known to make a close relationship among the "ostracoderms" unlikely, this has muddied the issue of the Hyperoartia's closest relatives. Traditionally the group was placed in a superclass

text: Cyclostomata

text: together with the

text: Myxini

text: (hagfishes). More recently, it has been proposed that the Myxini are more

text: basal

text: among the

text: skull-bearing chordates

text: , while the Hyperoartia are retained among vertebrates. But even though this may be correct, the lampreys represent one of the oldest divergences of the vertebrate lineage, and whether they are better united with some "ostracoderms" in the

text: Cephalaspidomorphi

text: , or not closer to these than to e.g. to other "ostracoderms" of the

text: Pteraspidomorphi

text: , or even the long-extinct

text: conodont

text: s, is still to be resolved. Even the very existence of the class Hyperoartia is disputed, with some analyses favoring a treatment of the "basal Hyperoartia" as a

text: monophyletic

text: lineage

text: Jamoytiiformes

text: that may in fact be very close to the ancestral

text: jawed vertebrates

text: On the vertebral column, from at least the middle of the back to over the middle of the tail, a tall crest of almost continuous height was present formed by spines that were about four times as high as the vertebral centra.

text: The New World leaf-nosed bats (Phyllostomidae) are found throughout Central and South America, from Mexico to northern Argentina. They are ecologically the most varied and diverse family within the order Chiroptera. Most species are insectivorous, but the phyllostomid bats include within their number true predatory species as well as frugivores (subfamily Stenodermatinae and Carolliinae). For example, the false vampire (Vampyrum spectrum), the largest bat in the Americas, eats vertebrate prey including small dove-sized birds.  Members of this family have evolved to use food groups such as fruit, nectar, pollen, insects, frogs, other bats, and small vertebrates, and, in the case of the vampire bats, even blood.

text: The New World leaf-nosed bats (Phyllostomidae) are found throughout

text: Central

text: and

text: South America

text: , from

text: Mexico

text: to northern

text: Argentina

text: . They are ecologically the most varied and diverse

text: family

text: within the

text: order

text: Chiroptera

text: . Most species are

text: insectivorous

text: , but the phyllostomid bats include within their number true predatory species as well as

text: frugivore

text: s (subfamily Stenodermatinae and Carolliinae). For example, the

text: false vampire

text: (Vampyrum spectrum), the largest bat in the

text: Americas

text: , eats vertebrate prey including small

text: dove

text: -sized birds.  Members of this family have evolved to use food groups such as fruit, nectar, pollen, insects, frogs, other bats, and small vertebrates, and, in the case of the

text: vampire bat

text: s, even

text: blood

text: Olson’s Extinction, in the Early Guadalupian (Roadian, Wordian), led to an extended period of low diversity when worldwide two-thirds of terrestrial vertebrate life was lost. Global diversity rose dramatically in the Capitanian, probably the result of disaster taxa filling empty guilds, only to fall again when the end-Guadalupian event caused a diversity drop in the Wuchiapingian.

text: Olson’s Extinction

text: , in the

text: Early Guadalupian

text: Roadian

text: Wordian

text: ), led to an extended period of low diversity when worldwide two-thirds of terrestrial vertebrate life was lost. Global diversity rose dramatically in the Capitanian, probably the result of disaster taxa filling empty guilds, only to fall again when the end-Guadalupian event caused a diversity drop in the

text: Wuchiapingian

text: The females of this species are capable of reproducing using parthenogenesis (that is, without males).

text: The females of this species are capable of reproducing using

text: parthenogenesis

text: (that is, without males).

text: Most are vertebrates, in which the notochord is replaced by the spinal column, which consists of a series of bony or cartilaginous cylindrical vertebrae, generally with neural arches that protect the spinal cord and with projections that link the vertebrae. Hagfish have incomplete braincases and no vertebrae, and are therefore not regarded as vertebrates,but as members of the craniates, the group from which vertebrates are thought to have evolved. The position of lampreys is ambiguous. They have complete braincases and rudimentary vertebrae, and therefore may be regarded as vertebrates and true fish. However, molecular phylogenetics, which uses biochemical features to classify organisms, has produced both results that group them with vertebrates and others that group them with hagfish.

text: Most are

text: vertebrate

text: s, in which the

text: notochord

text: is replaced by the

text: spinal column

text: , which consists of a series of bony or cartilaginous

text: cylindrical

text: vertebrae, generally with

text: neural arch

text: es that protect the

text: spinal cord

text: and with projections that link the vertebrae.

text: Hagfish

text: have incomplete

text: braincase

text: s and no vertebrae, and are therefore not regarded as vertebrates,but as members of the craniates, the group from which vertebrates are thought to have

text: evolved

text: . The position of

text: lamprey

text: s is ambiguous. They have complete braincases and rudimentary vertebrae, and therefore may be regarded as vertebrates and true

text: fish

text: . However,

text: molecular phylogenetics

text: , which uses

text: biochemical

text: features to classify organisms, has produced both results that group them with vertebrates and others that group them with hagfish.

text: "But it is harder to see how to resolve some of Gould's other claims about the large-scale history of life. Despite the plausibility of the distinction between disparity and diversity, we are not close to constructing a good account of disparity and its measurement". (p. 174) Further, convergent evolution belies the unpredictability that Gould supposes. However, "most examples of convergence are not independent of evolutionary experiments. For they concern lineages with an enormous amount of shared history, and hence shared developmental potential", as in "the standard example of streamlining in marine reptiles, sharks, pelagic bony fish like the tuna, and dolphins". (p. 175) Further, "the scale is not large enough. The fact that eyes have often evolved does not show that had, say, the earliest chordates succumbed to a bit of bad luck (and become extinct), then vertebrate-like organisms would have evolved again." (p. 175) Moreover, Gould's main concern is not with adaptive complexes, which are the source of the above, oft-cited examples, "but with body plans—basic ways of assembling organisms." Sterelny thinks that "we have to score Gould's contingency claims as: 'Don't know; and at this stage don't know how to find out'". (p. 175)

text: Electroreception occurred early in evolutionary history with the evolution of an ampullary sensory system that included receptors able to detect weak electric signals in the environment (less than 1ųV/cm or 50 Hz). Sense organs specialized for electroreception have only been found among vertebrates, and around 8.600 species are known to be electroreceptive. The majority of teleosts and amniotes do not have an electroreceptive system, but the distribution of electroreception in terms of evolution involves different classes of fish.  First, there is an origin of a common ancestor of current existent vertebrates (close to lampreys and gnathostomes). This ancestor evolved a lateral line that is important in processing sensory information and present in today’s hagfishes. Ampullary receptors are ancestral to jawed fish, for lampreys and agnathans were found to have ampullary receptors 400 million years earlier. Second, there is a loss of electroreception in amniotes. This could be due to the fact that air is a poor medium to effectively conduct the electric fields, unlike water. Third, there is also a loss of electroreception in gars, bowfin, and teleosts (neopterygian fishes). Ampullary receptors are present in all surviving cartilaginous fishes and bony fishes except a few species present in Neopterygii (which include gars, bowfins, and teleosts) Fourth, monotremes and a least three groups of fresh-water teleosts re-evolved electroreception. Fifth, a group of teleosts, Xenomystinae, acquired passive electrolocation with low frequency sensitive ampullary receptors. Sixth, another group of teleosts, Mormyroids, evolved passive electrolocation and active location, as well as a pulse type EOD in active electrolocation. Seventh, Silurifiormes and Gymnoformes evolved passive electrolocation, and Gymnoformes also evolved active electrolocation with a pulse type or wave type EODs.

text: Electroreception

text: occurred early in evolutionary history with the evolution of an ampullary sensory system that included receptors able to detect weak electric signals in the environment (less than 1ųV/cm or 50 Hz). Sense organs specialized for electroreception have only been found among vertebrates, and around 8.600 species are known to be electroreceptive. The majority of teleosts and amniotes do not have an electroreceptive system, but the distribution of electroreception in terms of evolution involves different classes of fish.  First, there is an origin of a common ancestor of current existent vertebrates (close to lampreys and gnathostomes). This ancestor evolved a lateral line that is important in processing sensory information and present in today’s hagfishes. Ampullary receptors are ancestral to jawed fish, for lampreys and agnathans were found to have ampullary receptors 400 million years earlier. Second, there is a loss of electroreception in amniotes. This could be due to the fact that air is a poor medium to effectively conduct the electric fields, unlike water. Third, there is also a loss of electroreception in gars, bowfin, and teleosts (

text: neopterygian

text: fishes). Ampullary receptors are present in all surviving cartilaginous fishes and bony fishes except a few species present in Neopterygii (which include gars, bowfins, and teleosts) Fourth, monotremes and a least three groups of fresh-water teleosts re-evolved electroreception. Fifth, a group of teleosts, Xenomystinae, acquired passive electrolocation with low frequency sensitive ampullary receptors. Sixth, another group of teleosts, Mormyroids, evolved passive electrolocation and active location, as well as a pulse type EOD in active electrolocation. Seventh, Silurifiormes and Gymnoformes evolved passive electrolocation, and Gymnoformes also evolved active electrolocation with a pulse type or wave type EODs.

text: The vertebral foramen is the large opening posterior to the vertebral body also known as the spinal canal. It contains and protects the spinal cord at the thoracic level.

text: The

text: vertebral foramen

text: is the large opening posterior to the vertebral body also known as the spinal canal. It contains and protects the spinal cord at the thoracic level.

text: This primary stage resolves completely within six months. The secondary stage occurs months to years later, with typically widespread skin lesions that vary in appearance, including "crab yaws" on the palms of the hands and soles of the feet with desquamation. These secondary lesions frequently ulcerate and are then highly infectious, but heal after six months or more. About 10% of people then go on to develop tertiary disease within five to ten years (during which further secondary lesions may come and go), with widespread bone, joint and soft tissue destruction, which may include extensive destruction of the bone and cartilage of the nose (Rhinopharyngitis mutilans or "gangosa").

text: This primary stage resolves completely within six months. The secondary stage occurs months to years later, with typically widespread skin lesions that vary in appearance, including "crab yaws" on the palms of the hands and soles of the feet with

text: desquamation

text: . These secondary lesions frequently ulcerate and are then highly infectious, but heal after six months or more. About 10% of people then go on to develop tertiary disease within five to ten years (during which further secondary lesions may come and go), with widespread bone, joint and

text: soft tissue

text: destruction, which may include extensive destruction of the bone and cartilage of the nose (

text: Rhinopharyngitis mutilans

text: or "

text: gangosa

text: When endothermy first appeared in the evolution of mammals is uncertain, though it is generally agreed to have first evolved in non-mammalian therapsids. Modern monotremes have lower body temperatures and more variable metabolic rates than marsupials and placentals, but there is evidence that some of their ancestors, perhaps including ancestors of the therians, may have had body temperatures like those of modern therians. Likewise, some modern therians like afrotheres and xenarthrans have secondarily developed lower body temperatures.

text: When

text: endothermy

text: first appeared in the evolution of mammals is uncertain, though it is generally agreed to have first evolved in non-mammalian

text: therapsids

text: . Modern monotremes have lower body temperatures and more variable metabolic rates than marsupials and placentals, but there is evidence that some of their ancestors, perhaps including ancestors of the therians, may have had body temperatures like those of modern therians. Likewise, some modern therians like afrotheres and xenarthrans have secondarily developed lower body temperatures.

text: Lampreys have vertebral arches, but nothing resembling the vertebral bodies found in all higher vertebrates. Even the arches are discontinuous, consisting of separate pieces of arch-shaped cartilage around the spinal cord in most parts of the body, changing to long strips of cartilage above and below in the tail region. Hagfishes lack a true vertebral column, and are therefore not properly considered vertebrates, but a few tiny neural arches are present in the tail. Hagfishes do, however, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as "Craniata" when discussing morphology. Molecular analysis since 1992 has suggested that the hagfishes are most closely related to lampreys, and so also are vertebrates in a monophyletic sense. Others consider them a sister group of vertebrates in the common taxon of Craniata.

text: Lamprey

text: s have vertebral arches, but nothing resembling the vertebral bodies found in all

text: higher vertebrates

text: . Even the arches are discontinuous, consisting of separate pieces of arch-shaped cartilage around the spinal cord in most parts of the body, changing to long strips of cartilage above and below in the tail region.

text: Hagfish

text: es lack a true vertebral column, and are therefore not properly considered vertebrates, but a few tiny neural arches are present in the tail. Hagfishes do, however, possess a

text: cranium

text: . For this reason, the vertebrate subphylum is sometimes referred to as "

text: Craniata

text: " when discussing morphology. Molecular analysis since 1992 has suggested that the hagfishes are most closely related to lampreys, and so also are vertebrates in a

text: monophyletic

text: sense. Others consider them a sister group of vertebrates in the common taxon of Craniata.

text: Recent studies in the ontogeny and evolution of paired appendages have compared finless vertebrates – such as lampreys – with chondricthyes, the most basal living vertebrate with paired fins. In 2006, researchers found that the same genetic programming involved in the segmentation and development of median fins was found in the development of paired appendages in catsharks.  Although these findings do not directly support the lateral fin-fold hypothesis, the original concept of a shared median-paired fin evolutionary developmental mechanism remains relevant.

text: Recent studies in the ontogeny and evolution of paired appendages have compared finless vertebrates – such as

text: lamprey

text: s – with

text: chondricthyes

text: , the most basal living vertebrate with paired fins. In 2006, researchers found that the same genetic programming involved in the segmentation and development of median fins was found in the development of paired appendages in

text: catshark

text: s.  Although these findings do not directly support the lateral fin-fold hypothesis, the original concept of a shared median-paired fin evolutionary developmental mechanism remains relevant.

text: 1942 Walls published The Vertebrate Eye and its Adaptive Radiation a classic on eye physiology and evolution. In this book Walls described a diversity of rod cells and cone cells in the animal world. He detected the communalities of photoreceptor cells in the vertebrate eye and was first in describing the cone cell as a specialized cell, obviously evolved from an early rod cell. 1958 Walls wrote a chapter in The eye in evolution, the first volume (780 pages) of Stewart Duke-Elder's work System of Ophthalmology, a monumental multivolume contribution to medical literature. In all, he published more than sixty journal papers and monographs, one book, and chapters to three other books.

text: 1942 Walls published The Vertebrate Eye and its Adaptive Radiation a classic on eye physiology and evolution. In this book Walls described a diversity of

text: rod cell

text: s and

text: cone cell

text: s in the animal world. He detected the communalities of

text: photoreceptor cell

text: s in the vertebrate eye and was first in describing the cone cell as a specialized cell, obviously evolved from an early rod cell. 1958 Walls wrote a chapter in The eye in evolution, the first volume (780 pages) of

text: Stewart Duke-Elder

text: 's work System of Ophthalmology, a monumental multivolume contribution to medical literature. In all, he published more than sixty journal papers and monographs, one book, and chapters to three other books.

text: The holotype specimen consists of the remains of a small individual. Because most of the vertebral column is absent, its body length cannot be directly determined, but a comparison can be made with the previously smallest known ornithomimosaur, the 1.6 metres long Shenzhousaurus, which has a thighbone length of 191 millimetres, while the femur length of Hexing is 135 millimetres. Such a small body size was among ornithomimosaurs up till now only known from juveniles but the holotype is not a young animal as is shown by the complete fusion of the skull bones, the neck ribs, the scapulocoracoid and the ankle bones.

text: The holotype specimen consists of the remains of a small individual. Because most of the vertebral column is absent, its body length cannot be directly determined, but a comparison can be made with the previously smallest known ornithomimosaur, the 1.6 metres long

text: Shenzhousaurus

text: , which has a thighbone length of 191 millimetres, while the femur length of Hexing is 135 millimetres. Such a small body size was among ornithomimosaurs up till now only known from juveniles but the holotype is not a young animal as is shown by the complete fusion of the skull bones, the neck ribs, the

text: scapulocoracoid

text: and the ankle bones.

text: A common theory on the evolution of pinealocytes is that they evolved from photoreceptor cells. It is speculated that in ancestral vertebrates, the pinealocytes served the same function as photoreceptor cells, such as retinal cells. Structural, functional, and genetic similarities exist between the two cell types. Structurally, both develop from the area of the brain designated the diencephalon, also the area containing the thalamus and hypothalamus, during embryological development. Both types of cells have similar features, including cilia, folded membranes, and polarity. Functional evidence for this theory of evolution can be seen in lower vertebrates. The retention of photosensitivity of the pinealocytes of lampreys, fish, amphibians, reptiles, and birds and the secretion of melatonin by some of these lower vertebrates suggests that pinealocytes may have once served as photoreceptor cells. Researchers have also indicated the presence of several proteins found in the retina in the pinealocytes in chicken and fish. Genetic evidence demonstrates that phototransduction genes present in the DNA of the retina are also present in the DNA of pinealocytes.

text: A common theory on the

text: evolution

text: of pinealocytes is that they evolved from

text: photoreceptor cell

text: s. It is speculated that in ancestral

text: vertebrate

text: s, the pinealocytes served the same function as photoreceptor cells, such as retinal cells. Structural, functional, and genetic similarities exist between the two cell types. Structurally, both develop from the area of the

text: brain

text: designated the

text: diencephalon

text: , also the area containing the

text: thalamus

text: and

text: hypothalamus

text: , during embryological development. Both types of cells have similar features, including

text: cilia

text: , folded membranes, and

text: polarity

text: . Functional evidence for this theory of evolution can be seen in lower vertebrates. The retention of photosensitivity of the pinealocytes of lampreys, fish, amphibians, reptiles, and birds and the secretion of

text: melatonin

text: by some of these lower vertebrates suggests that pinealocytes may have once served as photoreceptor cells. Researchers have also indicated the presence of several proteins found in the

text: retina

text: in the pinealocytes in chicken and fish. Genetic evidence demonstrates that

text: phototransduction

text: genes present in the

text: DNA

text: of the retina are also present in the DNA of pinealocytes.

text: Glanosuchus may have been one of the first therapsids to achieve endothermy, or warm-bloodedness. Endothermy is seen today in mammals, the only living group of therapsids. Reptiles, the closest living relatives of mammals, are cold-blooded ectotherms with lower metabolic rates. Endothermic animals likely evolved from more primitive ectothermic synapsids sometime in the Permian or Triassic.

text: Glanosuchus may have been one of the first therapsids to achieve endothermy, or warm-bloodedness. Endothermy is seen today in mammals, the only living group of therapsids.

text: Reptile

text: s, the closest living relatives of mammals, are cold-blooded

text: ectotherm

text: s with lower metabolic rates. Endothermic animals likely evolved from more primitive ectothermic

text: synapsid

text: s sometime in the Permian or

text: Triassic

text: As of 2014, it is not clear if Tyrannosaurus was endothermic (warm-blooded). Tyrannosaurus, like most dinosaurs, was long thought to have an ectothermic ("cold-blooded") reptilian metabolism. The idea of dinosaur ectothermy was challenged by scientists like Robert T. Bakker and John Ostrom in the early years of the "Dinosaur Renaissance", beginning in the late 1960s. Tyrannosaurus rex itself was claimed to have been endothermic ("warm-blooded"), implying a very active lifestyle. Since then, several paleontologists have sought to determine the ability of Tyrannosaurus to regulate its body temperature. Histological evidence of high growth rates in young Tyrannosaurus rex, comparable to those of mammals and birds, may support the hypothesis of a high metabolism. Growth curves indicate that, as in mammals and birds, Tyrannosaurus rex growth was limited mostly to immature animals, rather than the indeterminate growth seen in most other vertebrates.

text: As of 2014, it is not clear if Tyrannosaurus was

text: endothermic

text: (warm-blooded). Tyrannosaurus, like most dinosaurs, was long thought to have an

text: ectotherm

text: ic ("cold-blooded") reptilian

text: metabolism

text: . The idea of dinosaur ectothermy was challenged by scientists like

text: Robert T. Bakker

text: and

text: John Ostrom

text: in the early years of the "

text: Dinosaur Renaissance

text: ", beginning in the late 1960s. Tyrannosaurus rex itself was claimed to have been

text: endothermic

text: ("warm-blooded"), implying a very active lifestyle. Since then, several paleontologists have sought to determine the ability of Tyrannosaurus to

text: regulate

text: its body temperature. Histological evidence of high growth rates in young Tyrannosaurus rex, comparable to those of mammals and birds, may support the hypothesis of a high metabolism. Growth curves indicate that, as in mammals and birds, Tyrannosaurus rex growth was limited mostly to immature animals, rather than the

text: indeterminate growth

text: seen in most other

text: vertebrate

text: s.

text: The Hangenberg event affected both marine and freshwater communities. This mass extinction affected ammonites and trilobites, as well as jawed vertebrates, including tetrapod ancestors. The Hangenberg is linked to the extinction of 44% of high-level vertebrate clades, including all placoderms and most sarcopterygians, and the complete turnover of the vertebrate biota. 97 per cent of vertebrate species disappeared, with only smaller forms surviving. After the event only sharks less than a meter and most fishes and tetrapods less than 10 centimeters remained, and it would take 40 million years before they started to increase in size again. This led to the establishment of the modern vertebrate fauna, consisting mostly of actinopterygians, chondrichthyans, and tetrapods, in the Carboniferous. Romer's gap, a 15 million-year hiatus in the early Carboniferous tetrapod record, has been linked to this event. Also, some of the losses attributed to the Kellwasser event likely actually occurred during the Hangenberg extinction, due to the poor Famennian record for marine invertebrates.

text: The Hangenberg event affected both marine and freshwater communities. This mass extinction affected

text: ammonite

text: s and

text: trilobite

text: s, as well as jawed vertebrates, including

text: tetrapod

text: ancestors. The Hangenberg is linked to the extinction of 44% of high-level vertebrate

text: clade

text: s, including all placoderms and most

text: sarcopterygian

text: s, and the complete turnover of the vertebrate biota. 97 per cent of vertebrate species disappeared, with only smaller forms surviving. After the event only sharks less than a meter and most fishes and tetrapods less than 10 centimeters remained, and it would take 40 million years before they started to increase in size again. This led to the establishment of the modern vertebrate fauna, consisting mostly of actinopterygians, chondrichthyans, and tetrapods, in the

text: Carboniferous

text: Romer's gap

text: , a 15 million-year hiatus in the early Carboniferous tetrapod record, has been linked to this event. Also, some of the losses attributed to the Kellwasser event likely actually occurred during the Hangenberg extinction, due to the poor Famennian record for marine invertebrates.

text: Like all Plasmodium species P. parahexamerium has both vertebrate and insect hosts. The vertebrate hosts for this parasite are birds.

text: Like all Plasmodium species P. parahexamerium has both

text: vertebrate

text: and

text: insect

text: bird

text: s.

text: Sea levels in the Devonian were generally high. Marine faunas continued to be dominated by bryozoa, diverse and abundant brachiopods, the enigmatic hederelloids, microconchids and corals. Lily-like crinoids (animals, their resemblance to flowers notwithstanding) were abundant, and trilobites were still fairly common. Among vertebrates, jaw-less armored fish (ostracoderms) declined in diversity, while the jawed fish (gnathostomes) simultaneously increased in both the sea and fresh water. Armored placoderms were numerous during the lower stages of the Devonian Period and became extinct in the Late Devonian, perhaps because of competition for food against the other fish species. Early cartilaginous (Chondrichthyes) and bony fishes (Osteichthyes) also become diverse and played a large role within the Devonian seas. The first abundant genus of shark,  Cladoselache, appeared in the oceans during the Devonian Period. The great diversity of fish around at the time, have led to the Devonian being given the name "The Age of Fish" in popular culture.

text: Sea levels in the Devonian were generally high. Marine faunas continued to be dominated by

text: bryozoa

text: , diverse and abundant

text: brachiopods

text: , the enigmatic

text: hederelloids

text: microconchids

text: and

text: coral

text: s. Lily-like

text: crinoids

text: (animals, their resemblance to flowers notwithstanding) were abundant, and

text: trilobite

text: s were still fairly common. Among vertebrates, jaw-less armored fish (

text: ostracoderms

text: ) declined in diversity, while the jawed fish (gnathostomes) simultaneously increased in both the sea and

text: fresh water

text: . Armored

text: placoderms

text: were numerous during the lower stages of the Devonian Period and became extinct in the Late Devonian, perhaps because of competition for food against the other fish species. Early cartilaginous (

text: Chondrichthyes

text: ) and bony fishes (

text: Osteichthyes

text: ) also become diverse and played a large role within the Devonian seas. The first abundant genus of shark,

text: Cladoselache

text: , appeared in the oceans during the Devonian Period. The great diversity of fish around at the time, have led to the Devonian being given the name "The Age of Fish" in popular culture.

text: The intention of a chiropractic adjustment is to affect or correct the alignment, motion and/or function of a vertebral joint. Specifically, they are intended to correct "vertebral subluxations", the term given to the signs and symptoms that are said by chiropractors to result from abnormal alignment of vertebrae. (p. 218) This intention forms the legal and philosophical foundation of the profession, and US Medicare law formulates it in this manner:

text: The intention of a chiropractic adjustment is to affect or correct the alignment, motion and/or function of a vertebral joint. Specifically, they are intended to correct "

text: vertebral subluxation

text: s", the term given to the signs and symptoms that are said by chiropractors to result from abnormal alignment of vertebrae. (p. 218) This intention forms the legal and philosophical foundation of the profession, and

text: US Medicare

text: law formulates it in this manner:

text: In vertebrates, epithelium and mesenchyme are the basic tissue phenotypes. During embryonic development, migratory neural crest cells are generated by EMT involving the epithelial cells of the neuroectoderm. As a result, these cells dissociate from neural folds, gain motility, and disseminate to various parts of the embryo, where they differentiate to many other cell types. Also, craniofacial crest mesenchyme that forms the connective tissue forming the head and face, is formed by neural tube epithelium by EMT. EMT takes place during the construction of the vertebral column out of the extracellular matrix, which is to be synthesized by fibroblasts and osteoblasts that encircle the neural tube. The major source of these cells are sclerotome and somite mesenchyme as well as primitive streak. Mesenchymal morphology allows the cells to travel to specific targets in the embryo, where they differentiate and/or induce differentiation of other cells.

text: In vertebrates,

text: epithelium

text: and

text: mesenchyme

text: are the basic tissue phenotypes. During embryonic development, migratory

text: neural crest

text: cells are generated by EMT involving the epithelial cells of the neuroectoderm. As a result, these cells dissociate from neural folds, gain motility, and disseminate to various parts of the embryo, where they differentiate to many other cell types. Also, craniofacial crest mesenchyme that forms the connective tissue forming the head and face, is formed by

text: neural tube

text: epithelium by EMT. EMT takes place during the construction of the vertebral column out of the

text: extracellular matrix

text: , which is to be synthesized by

text: fibroblast

text: s and

text: osteoblast

text: s that encircle the neural tube. The major source of these cells are

text: sclerotome

text: and

text: somite

text: mesenchyme as well as

text: primitive streak

text: . Mesenchymal morphology allows the cells to travel to specific targets in the embryo, where they differentiate and/or induce differentiation of other cells.

text: Kenichthys is a genus of sarcopterygian fish from the Devonian period, and a member of the clade tetrapodomorpha.  The only known species of the genus is Kenichthys campbelli (named for the Australian palaeontologist K.S.W. Campbell), the first remains of which were found in China in 1993.  The genus is important to the study of the evolution of tetrapods due to the unique nature of its nostrils, which provide vital evidence regarding the evolutionary transition of fish-like nostrils to the vertebrate choanae.

text: Kenichthys is a genus of

text: sarcopterygian

text: fish from the

text: Devonian

text: period, and a member of the

text: clade

text: tetrapodomorpha

text: .  The only known

text: species

text: of the

text: genus

text: is Kenichthys campbelli (named for the

text: Australian

text: palaeontologist

text: K.S.W. Campbell), the first remains of which were found in

text: China

text: in 1993.  The genus is important to the study of the

text: evolution

text: of

text: tetrapod

text: s due to the unique nature of its

text: nostril

text: s, which provide vital evidence regarding the evolutionary transition of fish-like nostrils to the

text: vertebrate

text: choanae

text: By invertebrates are meant the non-vertebrate creatures of the kingdom Animalia (or Metazoa) in the biotic domain of Eukaryota.  By phyletic definition, these many-celled, sub-vertebrate animals lack a vertebral column, spinal column, vertebrae, backbone, or long, full-length notochord -- in contrast, of course, to the vertebrates in the one phylum of Chordata.

text: By invertebrates are meant the non-vertebrate creatures of the

text: kingdom

text: Animalia

text: (or

text: Metazoa

text: ) in the

text: biotic

text: domain

text: of

text: Eukaryota

text: .  By

text: phyletic

text: definition, these

text: many-celled

text: , sub-vertebrate animals lack a

text: vertebral column

text: spinal column

text: vertebrae

text: backbone

text: , or long, full-length

text: notochord

text: -- in contrast, of course, to the

text: vertebrate

text: s in the one phylum of

text: Chordata

text: If a non-vertebrate animal is mentioned below using its common, or vernacular name, the creature is usually a living, present-day invertebrate. But if  a non-vertebrate is cited below by its scientific, taxonomic genus (in italics), then it is typically an extinct invertebrate, known only from the fossil record.

text: If a non-vertebrate animal is mentioned below using its common, or vernacular name, the creature is usually a living,

text: present-day

text: invertebrate. But if  a non-vertebrate is cited below by its scientific,

text: taxonomic

text: genus

text: (in

text: italics

text: ), then it is typically an

text: extinct

text: invertebrate, known only from the

text: fossil record

text: These animals have evolved to survive the extreme pressure of the sub-photic zones. The pressure increases by about one bar every ten meters. To cope with the pressure, many fish are rather small, usually not exceeding 25 cm in length. Also, scientists have discovered that the deeper these creatures live, the more gelatinous their flesh and more minimal their skeletal structure. These creatures have also eliminated all excess cavities that would collapse under the pressure, such as swim bladders.

text: These animals have

text: evolved

text: to survive the extreme pressure of the sub-

text: photic zone

text: s. The pressure increases by about one

text: bar

text: every ten meters. To cope with the pressure, many fish are rather small, usually not exceeding 25 cm in length. Also, scientists have discovered that the deeper these creatures live, the more gelatinous their flesh and more minimal their skeletal structure. These creatures have also eliminated all excess cavities that would collapse under the pressure, such as

text: swim bladders

text: Gazin was born in Colorado in 1904. He got an education at California Institute of Technology and earned  bacheror's degree there in 1927. He got his master's degree in 1928 and a PhD in 1930, and during the same year he began working for the United States Geological Survey. He was named Assistant Curator in the Division of Vertebrate Paleontology at the Smithsonian Institution in 1932. Ten years later, in 1942 he became Associate Curator and in 1946, a Curator of the Division. He was named Senior Paleobiologist in 1967, and when his retirement came in 1970, he got a Paleobiologist Emeritus position. Twelve years later in 1982 he became a Curator Emeritus. He wrote ninety-nine works on vertebrate paleontology, most of which were focused on mammalian paleontology. Gazin served as President of the Society of Vertebrate Paleontology and was a Director of the American Geological Institute.

text: Gazin was born in

text: Colorado

text: in 1904. He got an education at

text: California Institute of Technology

text: and earned  bacheror's degree there in 1927. He got his master's degree in 1928 and a PhD in 1930, and during the same year he began working for the

text: United States Geological Survey

text: . He was named Assistant Curator in the

text: Division of Vertebrate Paleontology

text: at the

text: Smithsonian Institution

text: in 1932. Ten years later, in 1942 he became Associate Curator and in 1946, a Curator of the Division. He was named Senior Paleobiologist in 1967, and when his retirement came in 1970, he got a Paleobiologist Emeritus position. Twelve years later in 1982 he became a Curator Emeritus. He wrote ninety-nine works on vertebrate

text: paleontology

text: , most of which were focused on

text: mammal

text: ian paleontology. Gazin served as

text: President

text: of the

text: Society of Vertebrate Paleontology

text: and was a Director of the

text: American Geological Institute

text: The Sleeping Beauty transposon system is a synthetic DNA transposon designed to introduce precisely defined DNA sequences into the chromosomes of vertebrate animals for the purposes of introducing new traits and to discover new genes and their functions.

text: The Sleeping Beauty transposon system is a synthetic DNA

text: transposon

text: designed to introduce precisely defined

text: DNA

text: sequences into the

text: chromosomes

text: of

text: vertebrate

text: animals for the purposes of introducing new

text: traits

text: and to discover new

text: genes

text: and their functions.

text: The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. The brain and spinal cord together make up the central nervous system (CNS). The spinal cord begins at the occipital bone and extends down to the space between the first and second lumbar vertebrae; it does not extend the entire length of the vertebral column. It is around  in men and around  long in women.  Also, the spinal cord has a varying width, ranging from  thick in the cervical and lumbar regions to  thick in the thoracic area. The enclosing bony vertebral column protects the relatively shorter spinal cord. The spinal cord functions primarily in the transmission of neural signals between the brain and the rest of the body but also contains neural circuits that can independently control numerous reflexes and central pattern generators.The spinal cord has three major functions:as a conduit for motor information, which travels down the spinal cord, as a conduit for sensory information in the reverse direction, and finally as a center for coordinating certain reflexes.

text: The spinal cord is a long, thin, tubular bundle of

text: nervous tissue

text: and

text: support cells

text: that extends from the

text: medulla oblongata

text: in the

text: brainstem

text: to the

text: lumbar

text: region of the

text: vertebral column

text: . The brain and spinal cord together make up the

text: central nervous system

text: (CNS). The spinal cord begins at the

text: occipital bone

text: and extends down to the space between the first and second

text: lumbar vertebrae

text: ; it does not extend the entire length of the

text: vertebral column

text: . It is around  in men and around  long in women.  Also, the spinal cord has a varying width, ranging from  thick in the cervical and lumbar regions to  thick in the thoracic area. The enclosing bony

text: vertebral column

text: protects the relatively shorter spinal cord. The spinal cord functions primarily in the transmission of neural signals between the

text: brain

text: and the rest of the body but also contains

text: neural circuit

text: s that can independently control numerous

text: reflex

text: es and

text: central pattern generator

text: s.The spinal cord has three major functions:as a conduit for motor information, which travels down the spinal cord, as a conduit for sensory information in the reverse direction, and finally as a center for coordinating certain reflexes.

text: Other animals reproduce sexually with external fertilization, including many basal vertebrates. Vertebrates (such as reptiles, some fish, and most birds) reproduce with internal fertilization through cloacal copulation (see also hemipenis), while mammals copulate vaginally.

text: Other animals reproduce sexually with external fertilization, including many

text: basal

text: vertebrate

text: s. Vertebrates (such as

text: reptile

text: s, some

text: fish

text: , and most

text: bird

text: s) reproduce with internal fertilization through

text: cloaca

text: l copulation (see also

text: hemipenis

text: ), while

text: mammals copulate vagina

text: lly.

text: The holotype came from a single immature individual, based on the incomplete fusion of neural arches to their centra in the vertebral column. Siats is characterized by seven diagnostic, including four autapomorphic (i.e. unique), traits. Its autapomorphies include the subtriangular cross section of the distal caudal vertebrae, elongated centrodiapophyseal laminae lacking noticeable infradiapophyseal fossae on the proximal caudals, a transversely concaved acetabular rim of iliac pubic peduncle, and the presence of a notch on the end of the truncated lateral brevis shelf. Other notable traits include the broad neural spines on the dorsal vertebrae.

text: The holotype came from a single immature individual, based on the incomplete fusion of neural arches to their centra in the vertebral column. Siats is characterized by seven diagnostic, including four

text: autapomorphic

text: (i.e. unique), traits. Its autapomorphies include the subtriangular

text: cross section

text: of the

text: distal

text: caudal vertebrae, elongated centrodiapophyseal laminae lacking noticeable infradiapophyseal

text: fossae

text: on the

text: proximal

text: caudals, a transversely concaved acetabular rim of iliac pubic peduncle, and the presence of a notch on the end of the truncated lateral brevis shelf. Other notable traits include the broad

text: neural spines

text: on the dorsal vertebrae.

text: There are three anterior spinal veins in total. These, along with three posterior spinal veins, are allowed to communicate with one another as they run interconnected throughout the entire length of the spinal cord. This is seen through both sets of veins combining to form a network of anastomoses around the conus medullaris. Together, these two sets of veins also collect blood from intramedullary radial veins as well as other veins. They are drained by the anterior and posterior radicular veins, respectably. Radicular veins appear blue to the naked eye. Next, both radicular veins travel to the epidural space by means of joining the internal vertebral venous plexuses. Ultimately, this plexus is able to send and receive information from the veins and sinuses inside the brain. The external vertebral venous plexuses is also available for the internal vertebral venous plexus to communicate with.

text: There are three anterior spinal veins in total. These, along with three

text: posterior spinal veins

text: , are allowed to communicate with one another as they run interconnected throughout the entire length of the

text: spinal cord

text: . This is seen through both sets of veins combining to form a network of

text: anastomoses

text: around the

text: conus medullaris

text: . Together, these two sets of veins also collect blood from intramedullary radial veins as well as other veins. They are drained by the anterior and posterior radicular veins, respectably. Radicular veins appear blue to the naked eye. Next, both radicular veins travel to the epidural space by means of joining the

text: internal vertebral venous plexuses

text: . Ultimately, this plexus is able to send and receive information from the veins and sinuses inside the brain. The

text: external vertebral venous plexuses

text: is also available for the internal vertebral venous plexus to communicate with.

text: Vertebrate olfaction was first derived in an aquatic ecosystem, where water was the primary medium for odorants. Lancelets, a class of fish-like marine chordates, are the most distantly related ancestors that share the same olfactory receptors (OR) with humans. They diverged from our own ancestors approximately 700 million years ago, shortly before the development of the eyes and brain. Although they lack an identifiable olfactory organ, lancelets possess 40 olfactory receptor genes that are studded along their flanks to detect odor molecules from their surrounding aquatic environment. Furthermore, many vertebrate-type olfactory receptor genes were found in their genome.

text: Vertebrate olfaction was first derived in an aquatic

text: ecosystem

text: , where water was the primary medium for

text: odorants

text: Lancelet

text: s, a class of fish-like marine

text: chordate

text: s, are the most distantly related ancestors that share the same olfactory receptors (OR) with humans. They diverged from our own ancestors approximately 700 million years ago, shortly before the development of the eyes and brain. Although they lack an identifiable olfactory organ, lancelets possess 40 olfactory receptor genes that are studded along their flanks to detect odor molecules from their surrounding aquatic environment. Furthermore, many vertebrate-type olfactory receptor genes were found in their genome.

text: This technique/repair requires transplant sections of bone and cartilage. First, the damaged section of bone and cartilage is removed from the joint. Then a new healthy dowel of bone with its cartilage covering is punched out of the same joint and replanted into the hole left from removing the old damaged bone and cartilage. The healthy bone and cartilage are taken from areas of low stress in the joint so as to prevent weakening the joint. Depending on the severity and overall size of the damage multiple plugs or dowels may be required to adequately repair the joint, which becomes difficult for Osteochondral Autografts. The clinical results may deteriorate over time.

text: This technique/repair requires

text: transplant

text: sections of bone and

text: cartilage

text: . First, the damaged section of bone and cartilage is removed from the joint. Then a new healthy dowel of bone with its cartilage covering is punched out of the same joint and replanted into the hole left from removing the old damaged bone and cartilage. The healthy bone and cartilage are taken from areas of low stress in the joint so as to prevent weakening the joint. Depending on the severity and overall size of the damage multiple plugs or dowels may be required to adequately repair the joint, which becomes difficult for Osteochondral Autografts. The clinical results may deteriorate over time.

text: Wild-caught and hatchery-reared forms of this species have been transplanted and introduced for food or sport in at least 45 countries and every continent except Antarctica. Introductions to locations outside their native range in the United States (U.S.), Southern Europe, Australia, New Zealand and South America have damaged native fish species. Introduced populations may affect native species by preying on them, out-competing them, transmitting contagious diseases (such as whirling disease), or hybridizing with closely related species and subspecies, thus reducing genetic purity. Other introductions into waters previously devoid of any fish species or with severely depleted stocks of native fish have created world-class sport fisheries such as the Great Lakes and Wyoming's Firehole River.

text: Wild-caught and

text: hatchery

text: -reared forms of this species have been transplanted and introduced for food or sport in at least 45 countries and every continent except Antarctica. Introductions to locations outside their native range in the United States (U.S.),

text: Southern Europe

text: , Australia, New Zealand and South America have damaged native fish species. Introduced populations may affect native species by preying on them, out-competing them, transmitting contagious diseases (such as

text: whirling disease

text: ), or

text: hybridizing

text: with closely related species and subspecies, thus reducing genetic purity. Other introductions into waters previously devoid of any fish species or with severely depleted stocks of native fish have created world-class

text: sport fisheries

text: such as the Great Lakes and

text: Wyoming

text: 's

text: Firehole River

text: The evolution of the gene family in primitive vertebrates is not well understood. For example, it has been shown that the gene coding for the ancestral relaxin peptide existed independently from the other genes of the insulin superfamily, i.e. INS and IGF genes, in the early chordate ancestor. It is known that the genes coding for RLN3 and INSL5 arose from one ancestral gene, and INSL3 shares origin with RLN2 and its multiple duplicates. However the exact origins of the family still remain to be elucidated. Other studies attempted to show the existence of relaxin family peptide genes in the tunicate Ciona, but it has not been shown that any of these are in the same linkage group as modern relaxin genes. Multiple relaxin genes have also been identified in Amphioxus, but again syntenic relationship of these genes to modern relaxin genes is unclear and experimental work is lacking. A relaxin-like peptide, previously referred to as “Gonad Stimulating Substance” was also characterized in the echinoderm Patiria pectinifera (starfish). There is evidence that the starfish peptide is involved in reproductive processes and functions via a G-protein coupled receptor, which supports its relatedness to vertebrate relaxins.

text: The evolution of the gene family in primitive vertebrates is not well understood. For example, it has been shown that the gene coding for the ancestral relaxin peptide existed independently from the other genes of the insulin superfamily, i.e. INS and IGF genes, in the early chordate ancestor. It is known that the genes coding for RLN3 and INSL5 arose from one ancestral gene, and INSL3 shares origin with RLN2 and its multiple duplicates. However the exact origins of the family still remain to be elucidated. Other studies attempted to show the existence of relaxin family peptide genes in the tunicate Ciona, but it has not been shown that any of these are in the same linkage group as modern relaxin genes. Multiple relaxin genes have also been identified in Amphioxus, but again syntenic relationship of these genes to modern relaxin genes is unclear and experimental work is lacking. A relaxin-like peptide, previously referred to as “Gonad Stimulating Substance” was also characterized in the echinoderm

text: Patiria pectinifera

text: (starfish). There is evidence that the starfish peptide is involved in reproductive processes and functions via a G-protein coupled receptor, which supports its relatedness to vertebrate relaxins.

text: In other echinoderms, the endoskeleton is associated with a layer of muscle that allows the animal to move its arms or other body parts. This is entirely absent in sea urchins, which are unable to move in this way.

text: As with other vertebrae, each lumbar vertebra consists of a vertebral body and a vertebral arch.  The vertebral arch, consisting of a pair of pedicles and a pair of laminae, encloses the vertebral foramen (opening) and supports seven processes.

text: As with other vertebrae, each lumbar vertebra consists of a vertebral body and a vertebral arch.  The vertebral arch, consisting of a pair of pedicles and a pair of laminae, encloses the vertebral foramen (opening) and supports seven

text: processes

text: The pedicles are very strong, directed backward from the upper part of the vertebral body; consequently, the inferior vertebral notches are of considerable depth. The pedicles change in morphology from the upper lumbar to the lower lumbar. They increase in sagittal width from 9 mm to up to 18 mm at L5. They increase in angulation in the axial plane from 10 degrees to 20 degrees by L5. The pedicle is sometimes used as a portal of entrance into the vertebral body for fixation with pedicle screws or for placement of bone cement as with kyphoplasty or vertebroplasty.

text: The

text: pedicle

text: s are very strong, directed backward from the upper part of the vertebral body; consequently, the inferior vertebral notches are of considerable depth. The pedicles change in morphology from the upper lumbar to the lower lumbar. They increase in

text: sagittal

text: width from 9 mm to up to 18 mm at L5. They increase in angulation in the axial plane from 10 degrees to 20 degrees by L5. The pedicle is sometimes used as a portal of entrance into the vertebral body for fixation with pedicle screws or for placement of

text: bone cement

text: as with

text: kyphoplasty

text: or vertebroplasty.

text: Lifespan: For sexually reproducing planaria: "the life span of individual planarian can be as long as 3 years, likely due to the ability of neoblasts to constantly replace aging cells." Whereas for asexually reproducing planaria: "individual animals in clonal lines of some planarian species replicating by fission have been maintained for over 15 years."

text: Elfin forests occur at high elevations which are generally associated with low vertebrate biodiversity. Hummingbirds and bats make up large proportion of vertebrates in this area, usually as altitudinal migrants during seasonal shifts, such as for reproduction, or in response to food abundance. Other vertebrate species mostly include small rodents.

text: Elfin forests occur at high elevations which are generally associated with low vertebrate biodiversity. Hummingbirds and bats make up large proportion of vertebrates in this area, usually as

text: altitudinal migrants

text: during seasonal shifts, such as for reproduction, or in response to food abundance. Other vertebrate species mostly include small

text: rodent

text: s.

text: Since scientists cannot know much about the internal mechanisms of extinct creatures, most discussion focuses on homeothermy and tachymetabolism. However, it is generally agreed that endothermy first evolved in non-mammalian synapsids such as dicynodonts, which possess body proportions associated with heat retention, high vascularised bones with Haversian canals, and possibly hair.

text: Since scientists cannot know much about the internal mechanisms of extinct creatures, most discussion focuses on homeothermy and tachymetabolism. However, it is generally agreed that endothermy first evolved in non-mammalian synapsids such as

text: dicynodont

text: s, which possess body proportions associated with heat retention, high vascularised bones with

text: Haversian canal

text: s, and possibly hair.

text: D.E. Nilsson has independently put forth four theorized general stages in the evolution of a vertebrate eye from a patch of photoreceptors. Nilsson and S. Pelger published a classical paper theorizing how many generations are needed to evolve a complex eye in vertebrates. Another researcher, G.C. Young, has used fossil evidence to infer evolutionary conclusions, based on the structure of eye orbits and openings in fossilized skulls for blood vessels and nerves to go through. All this evidence adds to the growing amount of evidence that supports Darwin's theory.

text: Vertebrate Paleontology is an advanced textbook on vertebrate paleontology by Alfred Sherwood Romer, published by the University of Chicago Press. It went through three editions (1933, 1945, 1966) and for many years constituted a very authoritative work and the definitive coverage of the subject. A condensed version centering on comparative anatomy, coauthored by T.S. Parson came in 1977, remaining in print until 1985. The 1987 book Vertebrate Paleontology and Evolution by Robert L. Carroll is largely based on Romer's book.

text: Vertebrate Paleontology is an advanced textbook on

text: vertebrate paleontology

text: by

text: Alfred Sherwood Romer

text: , published by the

text: University of Chicago Press

text: . It went through three editions (1933, 1945, 1966) and for many years constituted a very authoritative work and the definitive coverage of the subject. A condensed version centering on

text: comparative anatomy

text: , coauthored by T.S. Parson came in 1977, remaining in print until 1985. The 1987 book

text: Vertebrate Paleontology and Evolution

text: by

text: Robert L. Carroll

text: is largely based on Romer's book.

text: The kype grows rapidly from bony needles proliferating from the tip of the dentary (the anterior and largest of the bones making up the lower jaw). The needles form a mesh, but do not interfere with the connective tissues used by bone marrow. At the snout, the needles strengthen into Sharpey's fibres. The speed at which the kype skeleton develops results in many osteoblasts and proteoglycans appearing along the growth zone. The dentary itself is made of compact bone, but the kype tissue contains chondrocytes and cartilage.  The kype formation process has been described as "making bone as fast as possible and with as little material as possible".

text: The kype grows rapidly from bony needles proliferating from the tip of the

text: dentary

text: (the anterior and largest of the bones making up the lower jaw). The needles form a mesh, but do not interfere with the connective tissues used by

text: bone marrow

text: . At the snout, the needles strengthen into

text: Sharpey's fibres

text: . The speed at which the kype skeleton develops results in many

text: osteoblasts

text: and

text: proteoglycan

text: s appearing along the growth zone. The dentary itself is made of

text: compact bone

text: , but the kype tissue contains

text: chondrocyte

text: s and

text: cartilage

text: .  The kype formation process has been described as "making bone as fast as possible and with as little material as possible".

text: Z. robustus is known from about 80% of the skull. However, no complete articulated skull is known, and most of the bones do not overlap and are found in isolation. Weishampel et al. found that these likely represented one individual, as the bones were from the same formation and are the same colour.  Four individuals were identified by Nopcsa for Z. robustus, and from these it can be seen that there is skeletal variation in the species. Like with the cranial material, vertebrae of Z. robustus are often found isolated. All regions of the vertebral column are represented in the fossil record, although no sternal plates have been found yet. The sacrum includes three vertebrae, with two sacrodorsals (dorsal vertebrae in the sacrum) and three sacrocaudals (caudal vertebrae in the sacrum). The limb and girdle bones are also well represented, with only the hands (manus) and feet (pes) mostly lacking.

text: Z. robustus is known from about 80% of the

text: skull

text: . However, no complete

text: articulated

text: skull is known, and most of the bones do not overlap and are found in isolation. Weishampel et al. found that these likely represented one individual, as the bones were from the same

text: formation

text: and are the same colour.  Four individuals were identified by Nopcsa for Z. robustus, and from these it can be seen that there is skeletal variation in the species. Like with the cranial material, vertebrae of Z. robustus are often found isolated. All regions of the

text: vertebral column

text: are represented in the fossil record, although no

text: sternal plates

text: have been found yet. The

text: sacrum

text: includes three vertebrae, with two sacrodorsals (dorsal vertebrae in the sacrum) and three sacrocaudals (caudal vertebrae in the sacrum). The limb and girdle bones are also well represented, with only the hands (

text: manus

text: ) and feet (

text: pes

text: ) mostly lacking.

text: The teleosts were first recognised as a distinct group by the German ichthyologist Johannes Peter Müller in 1844. The name is from Greek teleios, "complete" + osteon, "bone".  Müller based this classification on certain soft tissue characteristics which would prove to be problematic as it did not take into account the distinguishing features of fossil teleosts. In 1966, Greenwood et al. provided a more solid classification. The oldest teleost fossils date back to the late Triassic, evolving from fish related to the bowfins in the clade Holostei. During the Mesozoic and Cenozoic they diversified, and as a result, 96 percent of all known fish species are teleosts. The cladogram shows the relationship of the teleosts to other bony fish, and to the terrestrial vertebrates (tetrapods) that evolved from a related group of fish. Approximate dates are from Near et al., 2012.

text: The teleosts were first recognised as a distinct group by the German ichthyologist

text: Johannes Peter Müller

text: in 1844. The name is from

text: Greek

text: teleios, "complete" + osteon, "bone".  Müller based this classification on certain soft tissue characteristics which would prove to be problematic as it did not take into account the distinguishing features of fossil teleosts. In 1966, Greenwood et al. provided a more solid classification. The oldest teleost fossils date back to the late

text: Triassic

text: , evolving from fish related to the

text: bowfin

text: s in the

text: clade

text: Holostei. During the

text: Mesozoic

text: and

text: Cenozoic

text: they diversified, and as a result, 96 percent of all known fish species are teleosts. The

text: cladogram

text: shows the relationship of the teleosts to other bony fish, and to the terrestrial vertebrates (tetrapods) that evolved from a related group of fish. Approximate dates are from Near et al., 2012.

text: Some species of ectotherms including lizards and snakes, such as boa constrictors and tiger snakes,  increase their effective mass by clustering tightly together. It is also widespread amongst gregarious endotherms such as bats and birds (such as the mousebird and emperor penguin) where  it allows the sharing of body heat (particularly among juveniles).

text: Some species of ectotherms including

text: lizard

text: s and

text: snake

text: s, such as

text: boa constrictor

text: s and

text: tiger snake

text: s,  increase their effective mass by clustering tightly together. It is also widespread amongst gregarious endotherms such as

text: bat

text: s and birds (such as the

text: mousebird

text: and

text: emperor penguin

text: ) where  it allows the sharing of body heat (particularly among juveniles).

text: Whether one considers the eye to have evolved once or multiple times depends somewhat on the definition of an eye.  Much of the genetic machinery employed in eye development is common to all eyed organisms, which may suggest that their ancestor utilized some form of light-sensitive machinery – even if it lacked a dedicated optical organ.  However, even photoreceptor cells may have evolved more than once from molecularly similar chemoreceptors, and photosensitive cells probably existed long before the Cambrian explosion.  Higher-level similarities – such as the use of the protein crystallin in the independently derived cephalopod and vertebrate lenses – reflect the co-option of a protein from a more fundamental role to a new function within the eye.

text: Whether one considers the eye to have evolved once or multiple times depends somewhat on the definition of an eye.  Much of the genetic machinery employed in eye development is common to all eyed organisms, which may suggest that their ancestor utilized some form of light-sensitive machinery – even if it lacked a dedicated optical organ.  However, even photoreceptor cells may have evolved more than once from molecularly similar chemoreceptors, and photosensitive cells probably existed long before the Cambrian explosion.  Higher-level similarities – such as the use of the protein

text: crystallin

text: in the independently derived cephalopod and vertebrate lenses – reflect the

text: co-option

text: of a protein from a more fundamental role to a new function within the eye.

text: This insertion into the vertebral column is, however, not accepted by all observers.

text: Similar to all non-avian dinosaurs studied to date, Plateosaurus grew in a pattern that is unlike that of both extant mammals and birds. In the closely related sauropods with their typical dinosaurian physiology, growth was initially rapid, continuing somewhat more slowly well beyond sexual maturity, but was determinate, i.e. the animals stopped growing at a maximum size. Mammals grow rapidly, but sexual maturity falls typically at the end of the rapid growth phase. In both groups, the final size is relatively constant, with humans atypically variable. Extant reptiles show a sauropod-like growth pattern, initially rapid, then slowing after sexual maturity, and almost, but not fully, stopping in old age. However, their initial growth rate is much lower than in mammals, birds and dinosaurs. The reptilian growth rate is also very variable, so that individuals of the same age may have very different sizes, and final size also varies significantly. In extant animals, this growth pattern is linked to behavioural thermoregulation and a low metabolic rate (i.e. ectothermy), and is called "developmental plasticity". (Note that is not the same as neural developmental plasticity).

text: Similar to all non-avian dinosaurs studied to date, Plateosaurus grew in a pattern that is unlike that of both

text: extant

text: mammals and birds. In the closely related sauropods with their typical

text: dinosaurian physiology

text: , growth was initially rapid, continuing somewhat more slowly well beyond sexual maturity, but was determinate, i.e. the animals stopped growing at a maximum size. Mammals grow rapidly, but sexual maturity falls typically at the end of the rapid growth phase. In both groups, the final size is relatively constant, with humans atypically variable. Extant reptiles show a sauropod-like growth pattern, initially rapid, then slowing after sexual maturity, and almost, but not fully, stopping in old age. However, their initial growth rate is much lower than in mammals, birds and dinosaurs. The reptilian growth rate is also very variable, so that individuals of the same age may have very different sizes, and final size also varies significantly. In extant animals, this growth pattern is linked to

text: behavioural thermoregulation

text: and a low

text: metabolic

text: rate (i.e.

text: ectotherm

text: y), and is called "developmental plasticity". (Note that is not the same as neural

text: developmental plasticity

text: Gigantothermy allows animals to maintain body temperature, but is most likely detrimental to endurance and muscle power as compared with endotherms due to decreased anaerobic efficiency.  Mammals' bodies have roughly four times as much surface area occupied by mitochondria as reptiles.  Increased mitochondria, necessitating larger energy demands, and consequently producing more heat to thermoregulate.  An ectotherm the same size of an endotherm would not be able to remain as active as the endotherm, as heat is modulated behaviorally rather than biochemically.  More time is dedicated to basking than eating.  A large ectotherm, like a crocodile or alligator feeds by ambushing its prey whereas large mammals usually hunt.

text: A dermal bone or membrane bone is a bony structure derived from intramembranous ossification forming components of the vertebrate skeleton including much of the skull, jaws, gill covers, shoulder girdle and fin spines rays (lepidotrichia), and the shell (of tortoises and turtles).  In contrast to endochondral bone, dermal bone does not form from cartilage that then calcifies, and it is often ornamented. Dermal bone is formed within the dermis and grows by accretion only – the outer portion of the bone is deposited by osteoblasts.

text: A dermal bone or membrane bone is a bony structure derived from

text: intramembranous ossification

text: forming components of the

text: vertebrate

text: skeleton

text: including much of the

text: skull

text: jaw

text: s,

text: gill

text: covers, shoulder girdle and

text: fin

text: spines rays (

text: lepidotrichia

text: ), and the

text: shell

text: (of

text: tortoise

text: s and

text: turtle

text: s).  In contrast to

text: endochondral

text: bone, dermal bone does not form from cartilage that then calcifies, and it is often ornamented. Dermal bone is formed within the

text: dermis

text: and grows by accretion only – the outer portion of the bone is deposited by

text: osteoblast

text: s.

text: Langston worked on a number of different reptiles and amphibians in his long career, beginning with the 1950 description (with J. Willis Stovall) of the theropod dinosaur Acrocanthosaurus.  Langston was hired by the National Museum of Canada in 1954 to replace Charles M. Sternberg, and worked in western Canada and on Prince Edward Island until 1962.  One of his major finds, with Loris Russell, was the rediscovery of Sternberg's Scabby Butte Pachyrhinosaurus bonebed.  Langston, along with a small team of fieldworkers, excavated the Scabby Butte bonebed in 1957, securing several skulls and several hundred bones there. He then went on in 1969 to the University of Texas, becoming the second director of the Vertebrate Paleontology Laboratory, where he worked on many projects, including work on Cretaceous vertebrates from Big Bend National Park.  Finds that he and his students worked on include the giant pterosaur Quetzalcoatlus and a variety of Permian and Mesozoic reptiles.  He retired in 1986, but continued to be active in the field. In 2007, Langston was the twentieth recipient of the Society of Vertebrate Paleontology's A. S. Romer-G. G. Simpson Medal, the highest honor of the society.

text: Langston worked on a number of different reptiles and amphibians in his long career, beginning with the 1950 description (with

text: J. Willis Stovall

text: ) of the

text: theropod

text: dinosaur

text: Acrocanthosaurus

text: .  Langston was hired by the

text: National Museum of Canada

text: in 1954 to replace

text: Charles M. Sternberg

text: , and worked in western

text: Canada

text: and on

text: Prince Edward Island

text: until 1962.  One of his major finds, with Loris Russell, was the rediscovery of Sternberg's Scabby Butte

text: Pachyrhinosaurus

text: bonebed.  Langston, along with a small team of fieldworkers, excavated the Scabby Butte bonebed in 1957, securing several skulls and several hundred bones there. He then went on in 1969 to the University of Texas, becoming the second director of the Vertebrate Paleontology Laboratory, where he worked on many projects, including work on

text: Cretaceous

text: vertebrate

text: s from

text: Big Bend National Park

text: .  Finds that he and his students worked on include the giant

text: pterosaur

text: Quetzalcoatlus

text: and a variety of

text: Permian

text: and

text: Mesozoic

text: reptiles.  He retired in 1986, but continued to be active in the field. In 2007, Langston was the twentieth recipient of the

text: Society of Vertebrate Paleontology

text: 's

text: A. S. Romer

text: G. G. Simpson

text: Medal, the highest honor of the society.

text: The vertebral column consists of anywhere between 200 and 400 (or more) vertebrae. Tail vertebrae are comparatively few in number (often less than 20% of the total) and lack ribs, while body vertebrae each have two ribs articulating with them. The vertebrae have projections that allow for strong muscle attachment enabling locomotion without limbs.

text: Most other vertebrate animals have generally similar reproductive systems consisting of gonads, ducts, and openings. However, there is a great diversity of physical adaptations as well as reproductive strategies in every group of vertebrates.

text: Most other

text: vertebrate

text: animals have generally similar reproductive systems consisting of gonads, ducts, and openings. However, there is a great diversity of physical

text: adaptation

text: s as well as

text: reproductive strategies

text: in every group of vertebrates.

text: The cervical, thoracic and lumbar spine is composed of a total of 24 presacral vertebrae and their main functions are to protect the spinal cord, provide an attachment site for many muscles of the body. They also function by distributing one's bodyweight when standing upright.<ref>"Vertebral column". Encyclopedia Britannica. Encyclopedia Britannica Online. Encyclopedia Britannica Inc., 2015. Web. 16 Feb. 2015

text: The

text: cervical

text: thoracic

text: and

text: lumbar

text: spine is composed of a total of 24

text: presacral

text: vertebrae

text: and their main functions are to protect the spinal cord, provide an attachment site for many muscles of the body. They also function by distributing one's bodyweight when standing upright.<ref>"Vertebral column". Encyclopedia Britannica. Encyclopedia Britannica Online. Encyclopedia Britannica Inc., 2015. Web. 16 Feb. 2015

text: miR-199 has been shown to be a vertebrate specific miR family that emerge at the origin of the vertebrate lineage  Three paralogs of miR-199 can usually be found in non-teleost vertebrate species and 4 to 5 copies in the teleost species. All miR-199 genes are located on opposite strand of orthologous intron of Dynamin genes. Within Dynamin3 gene (Dnm3), miR-199 is associated with miR-214 and both miRs are transcribed together as a common primary transcript, demonstrated in mouse, human and zebrafish.

text: miR-199 has been shown to be a vertebrate specific miR family that emerge at the origin of the vertebrate lineage  Three paralogs of miR-199 can usually be found in non-teleost vertebrate species and 4 to 5 copies in the teleost species. All miR-199 genes are located on opposite strand of orthologous intron of

text: Dynamin

text: genes. Within

text: gene (Dnm3), miR-199 is associated with

text: and both miRs are transcribed together as a common primary transcript, demonstrated in mouse, human and zebrafish.

text: The long bones are those that are longer than they are wide. They are one of five types of bones: long, short, flat, irregular and sesamoid. Long bones, especially the femur and tibia, are subjected to most of the load during daily activities and they are crucial for skeletal mobility. They grow primarily by elongation of the diaphysis, with an epiphysis at each end of the growing bone. The ends of epiphyses are covered with hyaline cartilage ("articular cartilage").  The longitudinal growth of long bones is a result of endochondral ossification at the epiphyseal plate. Bone growth in length is stimulated by the production of growth hormone (GH), a secretion of the anterior lobe of the pituitary gland.

text: The long bones are those that are longer than they are wide. They are one of five types of

text: bone

text: s: long,

text: short

text: flat

text: irregular

text: and

text: sesamoid

text: . Long bones, especially the

text: femur

text: and

text: tibia

text: , are subjected to most of the load during daily activities and they are crucial for skeletal mobility. They grow primarily by elongation of the

text: diaphysis

text: , with an

text: epiphysis

text: at each end of the growing

text: bone

text: . The ends of epiphyses are covered with

text: hyaline cartilage

text: ("articular cartilage").  The longitudinal growth of long bones is a result of

text: endochondral ossification

text: at the

text: epiphyseal plate

text: . Bone growth in length is stimulated by the production of

text: growth hormone

text: (GH), a secretion of the

text: anterior lobe of the pituitary gland

text: The Romer-Simpson Medal is the highest award issued by the Society of Vertebrate Paleontology for "sustained and outstanding scholarly excellence and service to the discipline of vertebrate paleontology". The award in named in honor of Alfred S. Romer and George G. Simpson.

text: The Romer-Simpson Medal is the highest award issued by the

text: Society of Vertebrate Paleontology

text: for "sustained and outstanding scholarly excellence and service to the discipline of

text: vertebrate paleontology

text: ". The award in named in honor of

text: Alfred S. Romer

text: and

text: George G. Simpson

text: The human back is the large posterior area of the human body, rising from the top of the buttocks to the back of the neck and the shoulders. It is the surface of the body opposite from the chest. The vertebral column runs the length of the back and creates a central area of recession. The breadth of the back is created by the shoulders at the top and the pelvis at the bottom.

text: The human back is the large

text: posterior

text: area of the

text: human body

text: , rising from the top of the

text: buttock

text: s to the back of the

text: neck

text: and the shoulders. It is the

text: surface

text: of the body opposite from the

text: chest

text: . The

text: vertebral column

text: runs the length of the back and creates a central area of recession. The breadth of the back is created by the

text: shoulder

text: s at the top and the

text: pelvis

text: at the bottom.

text: Vertebrate Paleontology and Evolution is an advanced textbook on vertebrate paleontology by Robert L. Carroll, published in 1988 by WH Freeman.  It provides a very detailed technical account of various groups of living and fossil vertebrates.

text: Vertebrate Paleontology and Evolution is an advanced textbook on

text: vertebrate paleontology

text: by

text: Robert L. Carroll

text: , published in 1988 by

text: WH Freeman

text: .  It provides a very detailed technical account of various groups of living and fossil vertebrates.

text: Vertebrates originated about 525 million years ago during the Cambrian explosion, which saw the rise in organism diversity. The earliest known vertebrate is believed to be the Myllokunmingia. Another early vertebrate is Haikouichthys ercaicunensis. Unlike the other fauna that dominated the Cambrian, these groups had the basic vertebrate body plan: a notochord, rudimentary vertebrae, and a well-defined head and tail. All of these early vertebrates lacked jaws in the common sense and relied on filter feeding close to the seabed. A vertebrate group of uncertain phylogeny, small-eel-like conodonts, are known from microfossils of their paired tooth segments from the late Cambrian to the end of the Triassic.

text: Vertebrates originated about 525 million years ago during the

text: Cambrian explosion

text: , which saw the rise in organism diversity. The earliest known vertebrate is believed to be the

text: Myllokunmingia

text: . Another early vertebrate is

text: Haikouichthys ercaicunensis

text: . Unlike the other fauna that dominated the Cambrian, these groups had the basic vertebrate body plan: a notochord, rudimentary vertebrae, and a well-defined head and tail. All of these early vertebrates lacked

text: jaw

text: s in the common sense and relied on filter feeding close to the seabed. A vertebrate group of uncertain phylogeny, small-eel-like

text: conodont

text: s, are known from microfossils of their paired tooth segments from the late Cambrian to the end of the Triassic.

text: The structure of the dentine of eriptychiids is in many respects closer to that of heterostracans that to that of astraspids. This is the only argument to place them as the closest relatives to heterostracans, among the Ordovician vertebrates. However, eriptychiids differ from all other pteraspidomorphs in having a massively calcified endoskeleton, pervaded by canals for blood vessels.

text: The structure of the dentine of eriptychiids is in many respects closer to that of

text: heterostraca

text: ns that to that of

text: astraspids

text: . This is the only argument to place them as the closest relatives to heterostracans, among the Ordovician vertebrates. However, eriptychiids differ from all other pteraspidomorphs in having a massively calcified endoskeleton, pervaded by canals for blood vessels.

text: Although clearly not the normal procedure, a bare T-888 endoskeleton was able to grow itself a new flesh covering using 2007 technology (with the assistance of a geneticist and its own knowledge of future formula) by submerging itself in a blood-like bath. This improvised process resulted in a deformed covering that had the appearance of a burn victim and lacked its own biological eyes, requiring it to steal those of the geneticist and subsequently undergo cosmetic surgery to produce a more normal appearance.

text: Although clearly not the normal procedure, a bare

entity_name: List of Terminator: The Sarah Connor Chronicles characters

text: endoskeleton was able to grow itself a new flesh covering using 2007 technology (with the assistance of a geneticist and its own knowledge of future formula) by submerging itself in a blood-like

text: bath

text: . This improvised process resulted in a deformed covering that had the appearance of a burn victim and lacked its own biological

text: eye

text: s, requiring it to steal those of the

text: geneticist

text: and subsequently undergo

text: cosmetic surgery

text: to produce a more normal appearance.

text: Lobe-finned fishes, fish belonging to the class Sarcopterygii, are mostly extinct bony fishes, basally characterised by robust and stubby lobe fins containing a robust internal skeleton, cosmoid scales and internal nostrils. Their fins are fleshy, lobed, paired fins, joined to the body by a single bone. The fins of lobe-finned fish differ from those of all other fish in that each is borne on a fleshy, lobelike, scaly stalk extending from the body. The pectoral and pelvic fins are articulated in ways resembling the tetrapod limbs they were the precursors to. The fins evolved into the legs of the first tetrapod land vertebrates, amphibians. They also possess two dorsal fins with separate bases, as opposed to the single dorsal fin of ray-finned fish. The braincase of lobe-finned fishes primitively has a hinge line, but this is lost in tetrapods and lungfish. Many early lobe-finned fishes have a symmetrical tail. All lobe-finned fishes possess teeth covered with true enamel.

text: Lobe-finned fish

text: es, fish belonging to the class Sarcopterygii, are mostly extinct bony fishes, basally characterised by robust and stubby lobe fins containing a robust internal skeleton,

text: cosmoid scale

text: s and internal nostrils. Their fins are fleshy,

text: lobed

text: , paired fins, joined to the body by a single bone. The fins of lobe-finned fish differ from those of all other fish in that each is borne on a fleshy, lobelike, scaly stalk extending from the body. The

text: pectoral

text: and

text: pelvic fin

text: s are articulated in ways resembling the tetrapod limbs they were the precursors to. The fins evolved into the legs of the first tetrapod land vertebrates,

text: amphibian

text: s. They also possess two dorsal fins with separate bases, as opposed to the single dorsal fin of

text: ray-finned fish

text: . The braincase of lobe-finned fishes primitively has a hinge line, but this is lost in tetrapods and lungfish. Many early lobe-finned fishes have a symmetrical tail. All lobe-finned fishes possess teeth covered with true

text: enamel

text: Fairbank's disease or multiple epiphyseal dysplasia (MED) is a rare genetic disorder (dominant form: 1 in 10,000 births) that affects the growing ends of bones. Bones usually elongate by a process that involves the depositing of cartilage at the ends of the bones, called ossification. This cartilage then mineralizes and hardens to become bone. In MED, this process is defective.

text: Fairbank's disease or multiple epiphyseal dysplasia (MED) is a rare

text: genetic disorder

text: (dominant form: 1 in 10,000 births) that affects the

text: growing ends of bones

text: . Bones usually elongate by a process that involves the depositing of

text: cartilage

text: at the ends of the bones, called

text: ossification

text: . This cartilage then

text: mineralize

text: s and hardens to become bone. In MED, this process is defective.

text: Let's assume that there is another commodity that Crusoe can produce apart from coconuts, for example, fish. Now, Robinson has to decide how much time to spare for both activities, i.e. how many coconuts to gather and how many fish to hunt. The locus of the various combinations of fish and coconuts that he can produce from devoting different amounts of time to each activity is known as the production possibilities set. This is depicted in the figure 6:

text: The Xenopus model organism is responsible for large amounts of new knowledge on embryonic development and cell biology.  Xenopus has a number of unique experimental advantages as a vertebrate model. Paramount among these is the robustness of early embryos and their amenability to microinjection and microsurgery. This makes them a particularly attractive system for testing the ectopic activity of gene products and loss-of-function experiments using antagonizing reagents such as morpholinos, dominant-negatives and neomorphic proteins. Morpholinos are synthetic oligonucleotides that can be used to inhibit nuclear RNA splicing or mRNA translation and are the common gene inhibition reagent in Xenopus as neither siRNA or miRNA have yet been shown to reproducibly function in frog embryos. Xenopus embryos develop very quickly and form a full set of differentiated tissues within days of fertilization, allowing rapid analysis of the effects of manipulating embryonic gene expression. The large size of embryos and amenability to microinjection also makes them extremely well suited to microarray approaches. Furthermore, these same characteristics make Xenopus, one of the few vertebrate model organisms suited for chemical screens. Xenbase provides a large database of images illustrating the full genome, movies detailing embryogenesis, and multiple online tools useful for designing and conducting experiments using Xenopus.

text: The Xenopus

text: model organism

text: is responsible for large amounts of new knowledge on embryonic development and cell biology.

text: Xenopus

text: has a number of unique experimental advantages as a vertebrate model. Paramount among these is the robustness of early embryos and their amenability to microinjection and microsurgery. This makes them a particularly attractive system for testing the ectopic activity of gene products and loss-of-function experiments using antagonizing reagents such as morpholinos, dominant-negatives and neomorphic proteins.

text: Morpholino

text: s are synthetic

text: oligonucleotides

text: that can be used to inhibit nuclear RNA splicing or mRNA translation and are the common gene inhibition reagent in Xenopus as neither

text: siRNA

text: or

text: miRNA

text: have yet been shown to reproducibly function in frog embryos. Xenopus embryos develop very quickly and form a full set of differentiated tissues within days of fertilization, allowing rapid analysis of the effects of manipulating embryonic

text: gene expression

text: . The large size of embryos and amenability to microinjection also makes them extremely well suited to

text: microarray

text: approaches. Furthermore, these same characteristics make Xenopus, one of the few vertebrate model organisms suited for chemical screens. Xenbase provides a large database of images illustrating the full genome, movies detailing

text: embryogenesis

text: , and multiple online tools useful for designing and conducting experiments using Xenopus.

text: Beginning in 2000, Pilobolus published an annual wall calendar featuring original photography created to further explore and celebrate the company’s artistic sensibility. An introductory text to the 2008 calendar noted that the company had been “experimenting with still photography since the 1980s” to address the question “How can one select individual moments from a continuum and have them retain meaning?” The introduction also noted that the group’s “choreographic inquiry is driven by a fascination with images” that are, or become, “the fundamental units of our physical vocabulary.” Rather than attempting to document their live performances, the calendar photo shoots represented "a sort of annual gallery of our evolving understanding of the relationship between choreographic and photographic expression."

text: The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always externally visible. The skeleton, which forms the support structure inside the fish, is either made of cartilage, in cartilaginous fish, or bone in bony fish. The main skeletal element is the vertebral column, composed of articulating vertebrae which are lightweight yet strong. The ribs attach to the spine and there are no limbs or limb girdles. The main external features of the fish, the fins, are composed of either bony or soft spines called rays, which with the exception of the caudal fins, have no direct connection with the spine. They are supported by the muscles which compose the main part of the trunk. The heart has two chambers and pumps the blood through the respiratory surfaces of the gills and on round the body in a single circulatory loop. The eyes are adapted for seeing underwater and have only local vision. There is an inner ear but no external or middle ear. Low frequency vibrations are detected by the lateral line system of sense organs that run along the length of the sides of fish, and these respond to nearby movements and to changes in water pressure.

text: The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always externally visible. The skeleton, which forms the support structure inside the fish, is either made of cartilage, in

text: cartilaginous fish

text: , or bone in

text: bony fish

text: . The main skeletal element is the vertebral column, composed of articulating

text: vertebra

text: e which are lightweight yet strong. The ribs attach to the spine and there are no

text: limbs

text: or limb girdles. The main external features of the fish, the

text: fins

text: , are composed of either bony or soft spines called rays, which with the exception of the

text: caudal fin

text: s, have no direct connection with the spine. They are supported by the muscles which compose the main part of the trunk. The heart has two chambers and pumps the blood through the respiratory surfaces of the

text: gill

text: s and on round the body in a single circulatory loop. The eyes are adapted for seeing underwater and have only local vision. There is an inner ear but no external or

text: middle ear

text: . Low frequency vibrations are detected by the

text: lateral line

text: system of sense organs that run along the length of the sides of fish, and these respond to nearby movements and to changes in water pressure.

text: Bone is a rigid organ that constitutes part of the vertebral skeleton. Bones support and protect the various organs of the body, produce red and white blood cells, store minerals and also enable mobility.  Bone tissue is a type of dense connective tissue. Bones come in a variety of shapes and sizes and have a complex internal and external structure. They are lightweight yet strong and hard, and serve multiple functions. Mineralized osseous tissue or bone tissue, is of two types – cortical and cancellous and gives it rigidity and a coral-like three-dimensional internal structure. Other types of tissue found in bones include marrow, endosteum, periosteum, nerves, blood vessels and cartilage.

text: Bone is a

text: rigid

text: organ

text: that constitutes part of the

text: vertebral

text: skeleton

text: . Bones support and protect the various organs of the body, produce

text: red

text: and

text: white blood cell

text: s, store

text: mineral

text: s and also enable mobility.

text: Bone tissue

text: is a type of dense

text: connective tissue

text: . Bones come in a variety of shapes and sizes and have a complex internal and external

text: structure

text: . They are lightweight yet strong and hard, and serve multiple

text: functions

text: Mineralized

text: osseous tissue

text: or bone tissue, is of two types –

text: cortical

text: and

text: cancellous

text: and gives it rigidity and a

text: coral

text: -like three-dimensional internal structure. Other types of tissue found in bones include

text: marrow

text: endosteum

text: periosteum

text: nerve

text: s,

text: blood vessel

text: s and

text: cartilage

text: His more famous books include the widely praised Dinosaurs (1963) and  The Evidence of Evolution (1968). A major paper on the physiology of dinosaurs was "An Alternative to Dinosaur Endothermy: The Happy Wanderers" in A Cold Look at the Warm Blooded Dinosaurs (D.K. Thomas and E.C. Olson. eds., 1980), in which he countered Bob Bakker's theory of endothermic, or "warm-blooded" dinosaurs with a theory that migration helped large cold-blooded dinosaurs maintain a constant body temperature.

text: His more famous books include the widely praised Dinosaurs (1963) and  The Evidence of Evolution (1968). A major paper on the

text: physiology of dinosaurs

text: was "An Alternative to Dinosaur Endothermy: The Happy Wanderers" in A Cold Look at the Warm Blooded Dinosaurs (D.K. Thomas and E.C. Olson. eds., 1980), in which he countered

text: Bob Bakker

text: 's theory of

text: endothermic, or "warm-blooded"

text: dinosaurs with a theory that migration helped large cold-blooded dinosaurs maintain a constant body temperature.

text: Parthenogenesis is seen to occur naturally in aphids, Daphnia, rotifers, nematodes and some other invertebrates, as well as in many plants. Among vertebrates, strict parthenogenesis is only known to occur in lizards, snakes, birds and sharks, with fish, amphibians and reptiles exhibiting various forms of gynogenesis and hybridogenesis (an incomplete form of parthenogenesis). The first all-female (unisexual) reproduction in vertebrates was described in the fish Poecilia formosa in 1932. Since then at least 50 species of unisexual vertebrate have been described, including at least 20 fish, 25 lizards, a single snake species, frogs, and salamanders. Other, usually sexual, species may occasionally reproduce parthenogenetically and Komodo dragons; the hammerhead and blacktip sharks are recent additions to the known list of spontaneous parthenogenetic vertebrates. As with all types of asexual reproduction, there are both costs (low genetic diversity and therefore susceptibility to adverse mutations that might occur) and benefits (reproduction without the need for a male) associated with parthenogenesis.

text: Parthenogenesis is seen to occur naturally in

text: aphid

text: s,

text: Daphnia

text: rotifer

text: s,

text: nematode

text: s and some other invertebrates, as well as in many plants. Among

text: vertebrates

text: , strict parthenogenesis is only known to occur in lizards, snakes, birds and sharks, with fish, amphibians and reptiles exhibiting various forms of gynogenesis and hybridogenesis (an incomplete form of parthenogenesis). The first all-female (unisexual) reproduction in

text: vertebrates

text: was described in the fish

text: Poecilia formosa

text: in 1932. Since then at least 50 species of unisexual vertebrate have been described, including at least 20 fish, 25 lizards, a single snake species, frogs, and salamanders. Other, usually sexual, species may occasionally reproduce parthenogenetically and

text: Komodo dragon

text: s; the

text: hammerhead

text: and

text: blacktip shark

text: s are recent additions to the known list of spontaneous parthenogenetic vertebrates. As with all types of

text: asexual reproduction

text: , there are both costs (low genetic diversity and therefore susceptibility to adverse mutations that might occur) and benefits (reproduction without the need for a male) associated with parthenogenesis.

text: Cartilage differentiates from the condensations, giving rise to the skeletal primordia.  In most tetrapod limb skeletons (though not in some amphibians), the cartilage skeleton is replaced by bone later in development.

text: Cartilage

text: differentiates from the condensations, giving rise to the skeletal primordia.  In most tetrapod limb skeletons (though not in some amphibians), the cartilage skeleton is replaced by bone later in development.

text: Boa constrictors are ovoviviparous, giving birth to live young. They generally breed in the dry season—between April and August—and are polygynous, thus males may mate with multiple females. Half of all females breed in a given year, and a larger percentage of males actively attempt to locate a mate. Due to their polygynous nature, many of these males will be unsuccessful. As such, female boas in inadequate physical condition are unlikely to attempt to mate, or to produce viable young if they do mate. Reproduction in boas is almost exclusively sexual. Males ordinarily have a ZZ pair of sex determining chromosomes, and females a ZW pair. In 2010, a boa constrictor was shown to have reproduced asexually via parthenogenesis. The Colombian Rainbow boa, Epicrates maurus was found to reproduce by facultative parthenogenesis resulting in production of WW female progeny. The WW females were likely produced by terminal automixis (see Figure), a type of parthenogenesis in which two terminal haploid products of meiosis fuse to form a zygote, which then develops into a daughter progeny. This is only the third genetically confirmed case of consecutive virgin births of viable offspring from a single female within any vertebrate lineage.

text: Boa constrictors are

text: ovoviviparous

text: , giving birth to live young. They generally breed in the dry season—between April and August—and are

text: polygynous

text: , thus males may mate with multiple females. Half of all females breed in a given year, and a larger percentage of males actively attempt to locate a mate. Due to their polygynous nature, many of these males will be unsuccessful. As such, female boas in inadequate physical condition are unlikely to attempt to mate, or to produce viable young if they do mate. Reproduction in boas is almost exclusively sexual. Males ordinarily have a ZZ pair of sex determining chromosomes, and females a ZW pair. In 2010, a boa constrictor was shown to have reproduced asexually via

text: parthenogenesis

text: . The Colombian Rainbow boa, Epicrates maurus was found to reproduce by facultative

text: parthenogenesis

text: resulting in production of WW female progeny. The WW females were likely produced by terminal

text: automixis

text: (see Figure), a type of parthenogenesis in which two terminal haploid products of meiosis fuse to form a

text: zygote

text: , which then develops into a daughter progeny. This is only the third genetically confirmed case of consecutive virgin births of viable offspring from a single female within any

text: vertebrate

text: lineage.

text: The brachiocephalic artery or trunk is the first and largest artery that branches to form the right common carotid artery and the right subclavian artery. This artery provides blood to the right upper chest, right arm, neck, and head, through a branch called right vertebral artery. The right and left vertebral artery feed into the basilar artery and upward to the Posterior cerebral artery, which provides most of the brain with oxygenated blood.The posterior cerebral artery and the posterior communicating artery are within the circle of Willis.

text: The brachiocephalic artery or trunk is the first and largest

text: artery

text: that branches to form the

text: right common carotid

text: artery and the

text: right subclavian artery

text: . This artery provides blood to the right upper chest, right arm, neck, and head, through a branch called right

text: vertebral artery

text: . The right and left vertebral artery feed into the

text: basilar artery

text: and upward to the

text: Posterior cerebral artery

text: , which provides most of the brain with oxygenated blood.The

text: posterior cerebral artery

text: and the

text: posterior communicating artery

text: are within the circle of Willis.

text: In 2008, a 50-million-year-old fossil, Amphistium, was identified as an early relative of the flatfish and transitional fossil. In a typical modern flatfish, the head is asymmetric, with both eyes on one side of the head. In Amphistium, the transition from the typical symmetric head of a vertebrate is incomplete, with one eye placed near the top of the head. The researchers concluded,  "the change happened gradually, in a way consistent with evolution via natural selection—not suddenly, as researchers once had little choice but to believe."

text: In 2008, a 50-million-year-old fossil,

text: Amphistium

text: , was identified as an early relative of the flatfish and

text: transitional fossil

text: . In a typical modern flatfish, the head is asymmetric, with both eyes on one side of the head. In Amphistium, the transition from the typical symmetric head of a vertebrate is incomplete, with one eye placed near the top of the head. The researchers concluded,  "the change happened gradually, in a way consistent with evolution via

text: natural selection

text: —not suddenly, as researchers once had little choice but to believe."

text: Human OR genes have homologues in other mammals, such as mice, that demonstrate the evolution of Olfactory Receptor genes. One particular family that is involved in the initial event of odor perception has been found to be highly conserved throughout all of vertebrate evolution.

text: He has authored or co-authored over 100 articles and book chapters on vertebrate paleontology and paleoecology. Sues has edited Evolution of Herbivory in Terrestrial Vertebrates (Cambridge Univ. Press, 2000) and co-edited Terrestrial Ecosystems through Time (with A. K. Behrensmeyer et al.; Univ. of Chicago Press, 1992), In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods (with N. C. Fraser; Cambridge Univ. Press, 1994), and Major Transitions in Vertebrate Evolution (with J. S. Anderson; Indiana Univ. Press, 2007). He is also active in promoting the value of natural history collections for addressing major questions in current science.

text: He has authored or co-authored over 100 articles and book chapters on

text: vertebrate paleontology

text: and

text: paleoecology

text: . Sues has edited Evolution of Herbivory in Terrestrial Vertebrates (Cambridge Univ. Press, 2000) and co-edited Terrestrial Ecosystems through Time (with A. K. Behrensmeyer et al.; Univ. of Chicago Press, 1992), In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods (with N. C. Fraser; Cambridge Univ. Press, 1994), and Major Transitions in Vertebrate Evolution (with J. S. Anderson; Indiana Univ. Press, 2007). He is also active in promoting the value of natural history collections for addressing major questions in current science.

text: The cartilage of Gogoselachus was very different from those of other cartilaginous fish and acanthodians. While the cartilage itself closely resembled modern shark cartilage, the matrix holding the cartilage cells together contained remnant bone cells. This means that in contrast to the previous idea that cartilaginous fish were jawed vertebrates that evolved before the advent of a bony skeleton, cartilaginous fish in fact evolved from bony ancestors. Cartilaginous fish most likely lost these bony skeletons in order to evade predators and catch prey faster.

text: The cartilage of Gogoselachus was very different from those of other cartilaginous fish and acanthodians. While the cartilage itself closely resembled modern shark cartilage, the matrix holding the cartilage cells together contained remnant

text: bone cell

text: s. This means that in contrast to the previous idea that cartilaginous fish were

text: jawed vertebrates

text: that evolved before the advent of a bony skeleton, cartilaginous fish in fact evolved from bony ancestors. Cartilaginous fish most likely lost these bony skeletons in order to evade predators and catch prey faster.

text: The little tunny has some anatomical variations when compared to other species of Euthynnus.  E. alletteratus lacks a swim bladder, like most other tuna, so it must constantly keep moving to stay afloat.  The pectoral fins are crucial to the little tunny in maintaining its position in the water column.  Its liver is very disproportionate, with the right lobe much longer than the left or middle lobes. The stomach of the little tunny is a long sac that stretches almost the entire length of its body.  The intestinal tract is fairly short, coming from the left and right sides of the stomach, and extending without looping down the length of its body.  The different sections are characterized by their diameter and color. The ventral vertebral column of the little tunny has unique trelliswork, which is important to its family (Scombridae). Divided haemapophyses, or parts of the vertebrate forming a long canal, enclose the large ventral blood vessel.

text: For humans, one type of vertebrate, anatomical terms may differ from other forms of vertebrates. For one reason, this is because humans have a different neuraxis and, unlike animals that rest on four limbs, humans are considered when describing anatomy as being in the standard anatomical position. Thus what is on "top" of a human is the head, whereas the "top" of a dog may be its back, and the "top" of a flounder could refer to either its left or its right side.

text: For humans, one type of vertebrate, anatomical terms may differ from other forms of vertebrates. For one reason, this is because humans have a different

text: neuraxis

text: and, unlike animals that rest on four limbs, humans are considered when describing anatomy as being in the

text: standard anatomical position

text: . Thus what is on "top" of a human is the

text: head

text: , whereas the "top" of a dog may be its back, and the "top" of a

text: flounder

text: could refer to either its left or its right side.

text: These animals have evolved to survive the extreme pressure of the sub-photic zones. The pressure increases by about one atmosphere every ten meters. To cope with the pressure, many fish are rather small, usually not exceeding 25 cm in length. Also, scientists have discovered that the deeper these creatures live, the more gelatinous their flesh and more minimal their skeletal structure. These creatures have also eliminated all excess cavities that would collapse under the pressure, such as swim bladders.

text: These animals have

text: evolved

text: photic zone

text: s. The pressure increases by about one

text: atmosphere

text: every ten meters. To cope with the pressure, many fish are rather small, usually not exceeding 25 cm in length. Also, scientists have discovered that the deeper these creatures live, the more gelatinous their flesh and more minimal their skeletal structure. These creatures have also eliminated all excess cavities that would collapse under the pressure, such as swim bladders.

text: Indirect evidence for endothermy is provided by the body shape of derived ichthyosaurs, which with its short tail and vertical tail fin seems optimised for a high cruising speed that can only be sustained by a high metabolism: all extant animals swimming this way are either fully warm-blooded or, like sharks and tuna, maintain a high temperature in their body core. This argument does not cover basal forms with a more eel-like body and undulating swimming movement. In 1996, Richard Cowen, while accepting endothermy for the group, presumed that ichthyosaurs would have been subject to Carrier's constraint, a limitation to reptilian respiration pointed out in 1987 by David Carrier: their undulated locomotion forces the air out of the lungs and thus prevents them from taking breath while moving. Cowen hypothesised that ichthyosaurs would have overcome this problem by porpoising: constantly jumping out of the water would have allowed them to take a gulp of fresh air during each jump. Other researchers have tended to assume that for at least derived ichthyosaurs Carrier's constraint did not apply, because of their stiff bodies, which seems to be confirmed by their good diving capacity, implying an effective respiration and oxygen storage system. For these species porpoising was not a necessity. Nevertheless, ichthyosaurs would have often surfaced to breathe, probably tilting their heads slightly to take in air, because of the lower position of the nostrils compared to that of dolphins.

text: Indirect evidence for endothermy is provided by the body shape of derived ichthyosaurs, which with its short tail and vertical tail fin seems optimised for a high cruising speed that can only be sustained by a high metabolism: all extant animals swimming this way are either fully warm-blooded or, like sharks and tuna, maintain a high temperature in their body core. This argument does not cover basal forms with a more eel-like body and undulating swimming movement. In 1996,

text: Richard Cowen

text: , while accepting endothermy for the group, presumed that ichthyosaurs would have been subject to

text: Carrier's constraint

text: , a limitation to reptilian

text: respiration

text: pointed out in 1987 by

text: David Carrier

text: : their undulated locomotion forces the air out of the lungs and thus prevents them from taking breath while moving. Cowen hypothesised that ichthyosaurs would have overcome this problem by porpoising: constantly jumping out of the water would have allowed them to take a gulp of fresh air during each jump. Other researchers have tended to assume that for at least derived ichthyosaurs Carrier's constraint did not apply, because of their stiff bodies, which seems to be confirmed by their good diving capacity, implying an effective respiration and oxygen storage system. For these species porpoising was not a necessity. Nevertheless, ichthyosaurs would have often surfaced to breathe, probably tilting their heads slightly to take in air, because of the lower position of the nostrils compared to that of dolphins.

text: The Permian–Triassic extinction event wiped out almost all land vertebrates, as well as the great majority of other life. During the slow recovery from this catastrophe, estimated to have taken 30 million years, a previously obscure sauropsid group became the most abundant and diverse terrestrial vertebrates: a few fossils of archosauriformes ("ruling lizard forms") have been found in Late Permian rocks, but, by the Middle Triassic, archosaurs were the dominant land vertebrates. Dinosaurs distinguished themselves from other archosaurs in the Late Triassic, and became the dominant land vertebrates of the Jurassic and Cretaceous periods ().

text: The Permian–Triassic extinction event wiped out almost all land vertebrates, as well as the great majority of other life. During the slow recovery from this catastrophe, estimated to have taken 30 million years, a previously obscure sauropsid group became the most abundant and diverse terrestrial vertebrates: a few fossils of

text: archosauriformes

text: ("ruling lizard forms") have been found in Late Permian rocks, but, by the

text: Middle Triassic

text: , archosaurs were the dominant land vertebrates. Dinosaurs distinguished themselves from other archosaurs in the Late Triassic, and became the dominant land vertebrates of the Jurassic and Cretaceous periods ().

text: The vertebral column consists of a centrum (the central body or spine of the vertebra), vertebral arches which protrude from the top and bottom of the centrum, and various processes which project from the centrum or arches. An arch extending from the top of the centrum is called a neural arch, while the hemal arch or chevron is found underneath the centrum in the caudal (tail) vertebrae of fish. The centrum of a fish is usually concave at each end (amphicoelous), which limits the motion of the fish. This can be contrasted with the centrum of a mammal, which is flat at each end (acoelous), shaped in a manner that can support and distribute compressive forces.

text: The

text: vertebral column

text: consists of a

text: centrum

text: (the central body or spine of the vertebra),

text: vertebral arch

text: es which protrude from the top and bottom of the centrum, and various processes which project from the centrum or arches. An arch extending from the top of the centrum is called a neural arch, while the

text: hemal arch

text: or

text: chevron

text: is found underneath the centrum in the

text: caudal

text: (tail) vertebrae of fish. The centrum of a fish is usually concave at each end (amphicoelous), which limits the motion of the fish. This can be contrasted with the centrum of a mammal, which is flat at each end (acoelous), shaped in a manner that can support and distribute compressive forces.

text: These are protrusions of disc material into the surface of the vertebral body, which may contact the marrow of the vertebra and lead to inflammation. The protrusions are also associated with necrosis of the vertebral bone and the question of whether these protrusions and inflammation cause the necrosis, or whether the cartilage migrates into areas that have become necrotic due to other conditions, is under investigation.

text: These are protrusions of disc material into the surface of the vertebral body, which may contact the

text: marrow

text: of the vertebra and lead to

text: inflammation

text: . The protrusions are also associated with

text: necrosis

text: of the vertebral bone and the question of whether these protrusions and inflammation cause the necrosis, or whether the cartilage migrates into areas that have become necrotic due to other conditions, is under investigation.

text: Cladogram modified after Laurin, How Vertebrates Left the Water (2010).

text: Cladogram

text: modified after Laurin, How Vertebrates Left the Water (2010).

text: This technique contrasts with vertebral laminectomy in the amount of bone and muscle tissue that has to be removed, displaced, or dissected in the procedure.

text: This technique contrasts with vertebral

text: laminectomy

text: in the amount of bone and muscle tissue that has to be removed, displaced, or dissected in the procedure.

text: The most derived cynodonts are found within the clade Eucynodontia, which also contains the members of Mammalia. Representative genera of nonmammalian cynodonts include the large carnivorous cynognathids, the equally large herbivorous traversodonts, and the small mammal-like tritylodontids and ictidosaurs. The presence of respiratory turbinates suggests a rapid metabolism and possibly endothermy.

text: The most derived cynodonts are found within the

text: clade

text: Eucynodontia

text: , which also contains the members of

text: Mammal

text: ia. Representative genera of nonmammalian cynodonts include the large

text: carnivorous

text: cynognathids

text: , the equally large herbivorous

text: traversodont

text: s, and the small mammal-like

text: tritylodontid

text: s and

text: ictidosaur

text: s. The presence of

text: respiratory turbinates

text: suggests a rapid metabolism and possibly

text: endotherm

text: y.

text: Nearly all vertebrate species possess a pineal gland.  The most important exception is the hagfish, which is often thought of as the most primitive extant vertebrate.  Even in the hagfish, however, there may be a "pineal equivalent" structure in the dorsal diencephalon.  The lancelet Branchiostoma lanceolatum, the nearest existing relative to vertebrates, also lacks a recognizable pineal gland.  The lamprey (considered almost as primitive as the hagfish), however, does possess one.  A few more developed vertebrates lost pineal glands over the course of their evolution.

text: Nearly all vertebrate species possess a pineal gland.  The most important exception is the

text: hagfish

text: , which is often thought of as the most primitive extant vertebrate.  Even in the hagfish, however, there may be a "pineal equivalent" structure in the dorsal

text: diencephalon

text: .  The

text: lancelet

text: Branchiostoma lanceolatum

text: , the nearest existing relative to vertebrates, also lacks a recognizable pineal gland.  The

text: lamprey

text: (considered almost as primitive as the hagfish), however, does possess one.  A few more developed vertebrates lost pineal glands over the course of their evolution.

text: The defining characteristic of a vertebrate is the vertebral column, in which the notochord (a stiff rod of uniform composition) found in all chordates has been replaced by a segmented series of stiffer elements (vertebrae) separated by mobile joints (intervertebral discs, derived embryonically and evolutionarily from the notochord).

text: The defining characteristic of a vertebrate is the

text: vertebral column

text: , in which the

text: notochord

text: (a stiff rod of uniform composition) found in all

text: chordates

text: has been replaced by a segmented series of stiffer elements (vertebrae) separated by mobile joints (intervertebral discs, derived embryonically and evolutionarily from the notochord).

text: There are two regions where the spinal cord enlarges:Cervical enlargement - corresponds roughly to the brachial plexus nerves, which innervate the upper limb. It includes spinal cord segments from about C4 to T1. The vertebral levels of the enlargement are roughly the same (C4 to T1).Lumbosacral enlargement - corresponds to the lumbosacral plexus nerves, which innervate the lower limb. It comprises the spinal cord segments from L2 to S3 and is found about the vertebral levels of T9 to T12.

text: The vertebral column consisted of nine cervical vertebrae, fifteen or sixteen dorsal vertebrae, six of five sacral vertebrae and about forty-eight vertebrae of the tail. Much of the back and the tail was stiffened by long ossified tendons connecting the spines on top of the vertebrae. The processes on the underside of the tail vertebrae, the chevrons, were also connected by ossified tendons, which however were of a different form: they were shorter and split and frayed at one end, with the point of the sharp other end laying within the diverging end of the subsequent tendon. Furthermore, there were several counterdirectional rows of these, resulting in a herring-bone pattern completely immobilising the tail end.

text: The

text: vertebral column

text: consisted of nine cervical vertebrae, fifteen or sixteen dorsal vertebrae, six of five sacral vertebrae and about forty-eight vertebrae of the tail. Much of the back and the tail was stiffened by long ossified tendons connecting the spines on top of the vertebrae. The processes on the underside of the tail vertebrae, the chevrons, were also connected by ossified tendons, which however were of a different form: they were shorter and split and frayed at one end, with the point of the sharp other end laying within the diverging end of the subsequent tendon. Furthermore, there were several counterdirectional rows of these, resulting in a herring-bone pattern completely immobilising the tail end.

text: Janusiscus schultzei was a Gnathostomata (jawed vertebrate) dating from the Early Devonian period in Siberia, approximately 415 million years ago. It may be a common ancestor of either Chondrichthyes (cartilaginous fish) or Osteichthyes (bony fish) or both. If it is an ancestor to both types of fish, then J. schultzei would also be a common ancestor to all living jawed vertebrates. The species name is in honor of Hans-Peter Schultze.

text: Janusiscus schultzei was a

text: Gnathostomata

text: (jawed vertebrate) dating from the

text: Early Devonian

text: period in

text: Siberia

text: , approximately 415 million years ago. It may be a common ancestor of either

text: Chondrichthyes

text: (cartilaginous fish) or

text: Osteichthyes

text: (bony fish) or both. If it is an ancestor to both types of fish, then J. schultzei would also be a common ancestor to all living jawed vertebrates. The species name is in honor of

text: Hans-Peter Schultze

text: In January 2014, Nature reported research into the Australian ghostshark genome that showed they lack a single gene family that regulates the process of turning cartilage into bone, and indicates a gene duplication event gave rise to the transformation in bony vertebrates.

text: In January 2014,

text: Nature

text: reported research into the Australian ghostshark

text: genome

text: that showed they lack a single gene family that regulates the process of turning cartilage into bone, and indicates a

text: gene duplication

text: event gave rise to the transformation in bony

text: vertebrate

text: s.

text: The skeletal system serves many important functions; it provides the shape and form for the body, support and protection, allows bodily movement, produces blood for the body, and stores minerals. The number of bones in the human skeletal system is a controversial topic. Humans are born with over 300 bones; however, many bones fuse together between birth and maturity. As a result, an average adult skeleton consists of 206 bones. The number of bones varies according to the method used to derive the count. While some consider certain structures to be a single bone with multiple parts, others may see it as a single part with multiple bones. There are five general classifications of bones. These are long bones, short bones, flat bones, irregular bones, and sesamoid bones. The human skeleton is composed of both fused and individual bones supported by ligaments, tendons, muscles and cartilage. It is a complex structure with two distinct divisions; the axial skeleton, which includes the vertebral column, and the appendicular skeleton.

text: The skeletal system serves many important functions; it provides the shape and form for the body, support and protection, allows bodily movement, produces

text: blood

text: for the body, and stores minerals. The number of bones in the human skeletal system is a controversial topic. Humans are born with over 300 bones; however, many bones fuse together between birth and maturity. As a result, an average adult

text: skeleton

text: consists of 206 bones. The number of bones varies according to the method used to derive the count. While some consider certain structures to be a single bone with multiple parts, others may see it as a single part with multiple bones. There are five general classifications of bones. These are

text: long bones

text: short bones

text: flat bones

text: irregular bones

text: , and

text: sesamoid bones

text: . The human skeleton is composed of both fused and individual bones supported by

text: ligaments

text: tendons

text: muscles

text: and

text: cartilage

text: . It is a complex structure with two distinct divisions; the

text: axial skeleton

text: , which includes the

text: vertebral column

text: , and the

text: appendicular skeleton

text: The lungs of today's terrestrial vertebrates and the gas bladders of today's fish are believed to have evolved from simple sacs, as outpocketings of the esophagus, that allowed early fish to gulp air under oxygen-poor conditions. These outpocketings first arose in the  bony fish. In most of the ray-finned fish the sacs evolved into closed off gas bladders, while a number of carps, trouts, herrings, catfish, and eels have retained the physostome condition with the sack being open to the esophagus. In more basal bony fish, such as the gar, bichir, bowfin and the lobe-finned fish, the bladders have evolved to primarily function as lungs. The lobe-finned fish gave rise to the land-based tetrapods. Thus, the lungs of vertebrates are homologous to the gas bladders of fish (but not to their gills).

text: The lungs of today's terrestrial

text: vertebrate

text: s and the

text: gas bladder

text: s of today's

text: fish

text: are believed to have evolved from simple sacs, as outpocketings of the

text: esophagus

text: , that allowed early fish to gulp air under oxygen-poor conditions. These outpocketings first arose in the

text: bony fish

text: . In most of the

text: ray-finned fish

text: the sacs evolved into closed off gas bladders, while a number of

text: carp

text: s,

text: trout

text: s,

text: herring

text: s,

text: catfish

text: , and

text: eel

text: s have retained the

text: physostome

text: condition with the sack being open to the esophagus. In more basal bony fish, such as the

text: gar

text: bichir

text: bowfin

text: and the

text: lobe-finned fish

text: , the bladders have evolved to primarily function as lungs. The lobe-finned fish gave rise to the land-based

text: tetrapod

text: s. Thus, the lungs of vertebrates are

text: homologous

text: to the gas bladders of fish (but not to their

text: gill

text: s).

text: Acorn worms are considered more highly specialised and advanced than other similarly shaped worm-like creatures. They have a circulatory system with a heart that also functions as a kidney. Acorn worms have  gill-like structures that they use for breathing, similar to the gills of primitive fish. Therefore, acorn worms are sometimes said to be a link between classical invertebrates and vertebrates. Some also have a postanal tail which may be homologous to the post-anal tail of vertebrates. An interesting trait is that its three-section body plan is no longer present in the vertebrates, except for the anatomy of the frontal neural tube, later developed into a brain which is divided into three main parts. This means some of the original anatomy of the early chordate ancestors is still present even if it is not always visible.

text: Acorn worms are considered more highly specialised and advanced than other similarly shaped worm-like creatures. They have a circulatory system with a heart that also functions as a kidney. Acorn worms have  gill-like structures that they use for breathing, similar to the gills of primitive fish. Therefore, acorn worms are sometimes said to be a link between classical invertebrates and

text: vertebrate

text: s. Some also have a postanal tail which may be homologous to the post-anal tail of vertebrates. An interesting trait is that its three-section body plan is no longer present in the vertebrates, except for the anatomy of the frontal neural tube, later developed into a brain which is divided into three main parts. This means some of the original anatomy of the early chordate ancestors is still present even if it is not always visible.

text: These small vaguely eel- or snake-like animals are close relatives of vertebrates. The scientific name means "gill-mouth", referring to their anatomy – unlike vertebrates, they do not have a true head (with a skull capsule, eyes, nose, a well-developed brain etc.), but merely a mouth adjacent to the gill-slits, with the slightly enlarged anterior end of the dorsal nerve cord above and in front of them.

text: These small vaguely eel- or snake-like animals are close relatives of

text: vertebrate

text: s. The

text: scientific name

text: means "gill-mouth", referring to their

text: anatomy

text: – unlike vertebrates, they do not have a true

text: head

text: (with a

text: skull

text: capsule,

text: eye

text: s,

text: nose

text: , a well-developed

text: brain

text: etc.), but merely a mouth adjacent to the

text: gill

text: -slits, with the slightly enlarged

text: anterior

text: end of the

text: dorsal nerve cord

text: above and in front of them.

text: Antarctica's cold deserts have some of the least diverse fauna in the world. Terrestrial vertebrates are limited to sub-antarctic islands, and even then they are limited in number. Antarctica, including the subantarctic islands, has no natural fully terrestrial mammals, reptiles, or amphibians. Human activity has however led to the introduction in some areas of foreign species, such as rats, mice, chickens, rabbits, cats, pigs, sheep, cattle, reindeer, and various fish. Invertebrates, such as beetle species, have also been introduced.

text: Antarctica's cold deserts have some of the least diverse fauna in the world.

text: Terrestrial

text: vertebrates are limited to sub-antarctic islands, and even then they are limited in number. Antarctica, including the subantarctic islands, has no natural fully terrestrial mammals, reptiles, or amphibians. Human activity has however led to the introduction in some areas of

text: foreign species

text: , such as rats, mice, chickens, rabbits, cats, pigs, sheep, cattle,

text: reindeer

text: , and various fish. Invertebrates, such as beetle species, have also been introduced.

text: Sun bear scats collected in a forest reserve in Sabah contained mainly invertebrates such as beetles and their larvae, termites, and ants, followed by fruits and vertebrates. They break open decayed wood in search of termites, beetle larvae, and earthworms, and use their claws and teeth to break the standing termite mound into a few pieces. They quickly lick and suck the contents from the exposed mound, and also hold pieces of the broken mound with their front paws, while licking the termites from the surface of the mound. They consume figs in large amounts and eat them whole. Vertebrates consumed comprise birds, eggs, reptiles, turtles, deer and several unidentified small vertebrates. Hair or bone remains are rarely found in sun bear scat.

text: Sun bear scats collected in a forest reserve in

text: Sabah

text: contained mainly

text: invertebrate

text: s such as beetles and their larvae, termites, and ants, followed by fruits and

text: vertebrate

text: s. They break open decayed wood in search of termites, beetle larvae, and

text: earthworm

text: s, and use their claws and teeth to break the standing termite mound into a few pieces. They quickly lick and suck the contents from the exposed mound, and also hold pieces of the broken mound with their front paws, while licking the termites from the surface of the mound. They consume figs in large amounts and eat them whole. Vertebrates consumed comprise

text: bird

text: s,

text: eggs

text: reptiles

text: turtle

text: s,

text: deer

text: and several unidentified small vertebrates. Hair or bone remains are rarely found in sun bear scat.

text: Thermoregulation in organisms runs along a spectrum from endothermy to ectothermy. Endotherms create most of their heat via metabolic processes, and are colloquially referred to as warm-blooded. Ectotherms use external sources of temperature to regulate their body temperatures. They are colloquially referred to as cold-blooded despite the fact that body temperatures often stay within the same temperature ranges as warm-blooded animals.

text: Thermoregulation in organisms runs along a spectrum from

text: endotherm

text: y to

text: ectotherm

text: y.

text: Endotherm

text: s create most of their heat via metabolic processes, and are colloquially referred to as

text: warm-blooded

text: Ectotherm

text: s use external sources of temperature to regulate their body temperatures. They are colloquially referred to as

text: cold-blooded

text: despite the fact that body temperatures often stay within the same temperature ranges as warm-blooded animals.

text: In most vertebrates, the main skeletal component is referred to as bone. Another important component is cartilage which in mammals is found mainly in the joint areas. In other animals, such as the cartilaginous fishes, which include the sharks, the skeleton is composed entirely of cartilage. The segmental pattern of the skeleton is present in all vertebrates (mammals, birds, fish, reptiles and amphibians) with basic units being repeated. This segmental pattern is particularly evident in the vertebral column and the ribcage.

text: In most

text: vertebrate

text: s, the main skeletal component is referred to as

text: bone

text: . Another important component is

text: cartilage

text: which in mammals is found mainly in the joint areas. In other animals, such as the cartilaginous fishes, which include the

text: shark

text: s, the skeleton is composed entirely of cartilage. The

text: segmental

text: pattern of the skeleton is present in all

text: vertebrate

text: s (mammals, birds, fish, reptiles and amphibians) with basic units being repeated. This segmental pattern is particularly evident in the vertebral column and the ribcage.

text: Providing they receive approval from the U.S. Food and Drug Administration (FDA), another new type of fish may be arriving soon. The "AquAdvantage salmon", engineered to reach maturity within roughly 18 months (as opposed to three years in the wild), could help meet growing global demand. There are health and environmental concerns associated with the introduction any new GMO, but more importantly this scenario highlights the potential economic impact a new product may have. The FDA does perform an economic impact analysis to weigh, for example, the consequences these new genetically modified fish may have on the traditional salmon fishing industry against the long term gain of a cheaper, more plentiful source of salmon. These technoethical assessments, which regulatory organizations like the FDA are increasingly faced with worldwide, are vitally important in determining how GMOs—with all of their potential beneficial and harmful effects—will be handled moving forward.

text: Providing they receive approval from the U.S.

text: Food and Drug Administration

text: (FDA), another new type of fish may be arriving soon. The "

text: AquAdvantage salmon

text: ", engineered to reach maturity within roughly 18 months (as opposed to three years in the wild), could help meet growing global demand. There are health and environmental concerns associated with the introduction any new GMO, but more importantly this scenario highlights the potential economic impact a new product may have. The FDA does perform an

text: economic impact analysis

text: to weigh, for example, the consequences these new

text: genetically modified fish

text: may have on the traditional salmon fishing industry against the long term gain of a cheaper, more plentiful source of salmon. These technoethical assessments, which regulatory organizations like the FDA are increasingly faced with worldwide, are vitally important in determining how GMOs—with all of their potential beneficial and harmful effects—will be handled moving forward.

text: The taxonomy of the vertebrates presented by John Zachary Young in The Life of Vertebrates (1962) is a system of classification with emphasis on this group of animals.

text: The taxonomy of the vertebrates presented by

text: John Zachary Young

text: in

text: The Life of Vertebrates

text: (1962) is a system of classification with emphasis on this group of animals.

text: While clinicians almost unanimously refer to the syndrome as "Jarcho-Levin", reports have variously labelled or referred to the condition as all of the following: Hereditary malformations of the vertebral bodies, hereditary multiple hemivertebrae, syndrome of bizarre vertebral anomalies, spondylocostal dysplasia, spondylothoracic dysplasia, costovertebral anomalies, costovertebral dysplasia, spondylothoracic dysplasia, occipito-facial-cervico-thoracic-abdomino-digital dysplasia (deemed "ridiculously long" and "unwarranted" by OMIM), and spondylocostal dysostosis.

text: While

text: clinicians

text: almost unanimously refer to the syndrome as "Jarcho-Levin", reports have variously labelled or referred to the condition as all of the following: Hereditary malformations of the vertebral bodies, hereditary multiple hemivertebrae, syndrome of bizarre vertebral anomalies, spondylocostal dysplasia, spondylothoracic dysplasia, costovertebral anomalies, costovertebral dysplasia, spondylothoracic dysplasia, occipito-facial-cervico-thoracic-abdomino-digital dysplasia (deemed "ridiculously long" and "unwarranted" by OMIM), and spondylocostal dysostosis.

text: Like all Plasmodium species P. hermani has both vertebrate and insect hosts. The vertebrate hosts for this parasite are birds.

text: Like all Plasmodium species P. hermani has both

text: vertebrate

text: and

text: insect

text: bird

text: s.

text: The caudal fin is homocercal, meaning the upper and lower lobes are about equal in size. The spine ends at the caudal peduncle, the base of the caudal fin, distinguishing this group from those in which the spine extends into the upper lobe of the caudal fin, such as most fish from the Paleozoic (541 to 252 million years ago). The neural arches are elongated to form uroneurals which provide support for this upper lobe. In addition, the hypurals, bones that form a flattened plate at the posterior end of the vertebral column, are enlarged providing further support for the caudal fin. In general, teleosts tend to be quicker and more flexible than more basal bony fishes. Their skeletal structure has evolved towards greater lightness. While teleost bones are well calcified, they are constructed from a scaffolding of struts, rather than the dense cancellous bones of holostean fish. In addition, the lower jaw of the teleost is reduced to just three bones; the dentary, the angular bone and the articular bone.

text: The

text: caudal fin

text: is

text: homocercal

text: , meaning the upper and lower lobes are about equal in size. The spine ends at the caudal peduncle, the base of the caudal fin, distinguishing this group from those in which the spine extends into the upper lobe of the caudal fin, such as most fish from the

text: Paleozoic

text: (541 to 252 million years ago). The neural arches are elongated to form uroneurals which provide support for this upper lobe. In addition, the

text: hypurals

text: , bones that form a flattened plate at the posterior end of the vertebral column, are enlarged providing further support for the caudal fin. In general, teleosts tend to be quicker and more flexible than more basal bony fishes. Their skeletal structure has evolved towards greater lightness. While teleost bones are well

text: calcified

text: , they are constructed from a scaffolding of struts, rather than the dense

text: cancellous bone

text: s of

text: holostean

text: fish. In addition, the lower jaw of the teleost is reduced to just three bones; the

text: dentary

text: , the

text: angular bone

text: and the

text: articular bone

text: The technical principles for the surgical reconstruction of a nose derive from the essential operative principles of plastic surgery: that the applied procedure and technique(s) yield the most satisfactory functional and aesthetic outcome. Hence, the rhinoplastic reconstruction of a new nasal subunit, of virtually normal appearance, can be done in a few procedural stages, using intranasal tissues to correct defects of the mucosa; cartilage battens to brace against tissue contraction and depression (topographic collapse); axial skin flaps designed from three-dimensional (3-D) templates derived from the topographic subunits of the nose; and the refinement of the resultant correction with the subcutaneous sculpting of bone, cartilage, and flesh. Nonetheless, the physician-surgeon and the rhinoplasty patient must abide the fact that the reconstructed nasal subunit is not a nose proper, but a collagen-glued collage—of forehead skin, cheek skin, mucosa, vestibular lining, nasal septum, and fragments of ear cartilage—which is perceived as a nose only because its contour, skin color, and skin texture are true to the original nose.

text: The technical principles for the

text: surgical

text: reconstruction of a

text: nose

text: derive from the essential operative principles of

text: plastic surgery

text: : that the applied procedure and technique(s) yield the most satisfactory functional and aesthetic outcome. Hence, the rhinoplastic reconstruction of a new nasal subunit, of virtually normal appearance, can be done in a few procedural stages, using intranasal tissues to correct defects of the

text: mucosa

text: cartilage

text: battens to brace against

text: tissue

text: contraction and depression (topographic collapse); axial

text: skin flaps

text: designed from three-dimensional (3-D) templates derived from the topographic subunits of the nose; and the refinement of the resultant correction with the subcutaneous sculpting of

text: bone

text: , cartilage, and flesh. Nonetheless, the physician-surgeon and the rhinoplasty patient must abide the fact that the reconstructed nasal subunit is not a nose proper, but a

text: collagen

text: -glued collage—of forehead skin, cheek skin, mucosa, vestibular lining, nasal septum, and fragments of

text: ear

text: cartilage—which is perceived as a nose only because its contour, skin color, and skin texture are true to the original nose.

text: The primary issue to be considered in off-Earth reproduction is the lack of gravitational acceleration.  Life on Earth, and thus the reproductive and ontogenetic processes of all extant species and their ancestors, evolved under the constant influence of the Earth's 1g gravitational field. It is imperative to study how space environment affects critical phases of mammalian reproduction and development as well as events surrounding fertilization, embryogenesis, pregnancy, birth, postnatal maturation, and parental care. Gravity affects all aspects of vertebrate development, including cell structure and function, organ system development, and even behavior. As gravity regulates mammalian gene expression, there are significant implications for successful procreation in an extraterrestrial environment.

text: The primary issue to be considered in off-Earth reproduction is the lack of gravitational acceleration.  Life on Earth, and thus the reproductive and ontogenetic processes of all extant species and their ancestors, evolved under the constant influence of the Earth's 1

text: g

text: gravitational field. It is imperative to study how space environment affects critical phases of mammalian reproduction and development as well as events surrounding fertilization, embryogenesis, pregnancy, birth, postnatal maturation, and parental care. Gravity affects all aspects of vertebrate development, including cell structure and function, organ system development, and even behavior. As gravity regulates mammalian gene expression, there are significant implications for successful procreation in an extraterrestrial environment.

text: Studies of vertebrates have shown support for the division of the Jehol into phases, and the diversity of fish in the Yixian was distinct from older and younger formations, with Lycoptera as the dominant species. The Yixian preserves the first Jehol dinosaurs and pterosaurs (which have not been found in the older Dabeigou Formation), and the first major radiation of birds (only one bird species is known from the Dabeigou). The Yixian also preserves the largest (and only) mammal radiation so far known from the Jehol group. Most vertebrates showed a tendency to climb trees or become arboreal, including many tree-dwelling birds, and climbing mammals and lizards.

text: Studies of

text: vertebrate

text: s have shown support for the division of the Jehol into phases, and the diversity of

text: fish

text: in the Yixian was distinct from older and younger formations, with

text: Lycoptera

text: as the dominant species. The Yixian preserves the first Jehol

text: dinosaur

text: s and

text: pterosaur

text: s (which have not been found in the older Dabeigou Formation), and the first major radiation of

text: bird

text: s (only one bird species is known from the Dabeigou). The Yixian also preserves the largest (and only)

text: mammal

text: radiation so far known from the Jehol group. Most vertebrates showed a tendency to climb trees or become

text: arboreal

text: , including many tree-dwelling birds, and climbing mammals and lizards.

text: In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical and lumbar vertebrae; they increase in size going towards the lumbar vertebrae, with the lower ones being a lot larger than the upper. They are distinguished by the presence of facets on the sides of the bodies for articulation with the heads of the ribs, and facets on the transverse processes of all, except the eleventh and twelfth, for articulation with the tubercles of the ribs. By convention, the human thoracic vertebrae are numbered T1–T12, with the first one (T1) located closest to the skull and the others going down the spine towards the lumbar region.

text: In

text: vertebrates

text: , thoracic vertebrae compose the middle segment of the

text: vertebral column

text: , between the

text: cervical vertebrae

text: and the

text: lumbar vertebrae

text: . In humans, there are twelve thoracic

text: vertebrae

text: and they are intermediate in size between the cervical and lumbar vertebrae; they increase in size going towards the lumbar vertebrae, with the lower ones being a lot larger than the upper. They are distinguished by the presence of

text: facets

text: on the sides of the bodies for

text: articulation

text: with the

text: heads of the ribs

text: , and facets on the

text: transverse process

text: es of all, except the eleventh and twelfth, for articulation with the

text: tubercles of the rib

text: s. By convention, the human thoracic vertebrae are numbered T1–T12, with the first one (T1) located closest to the skull and the others going down the spine towards the lumbar region.

text: Certain infections can also lead to the development of Kyphoscoliosis such as vertebral tuberculosis or general tuberculosis. Osteochondrodysplasia, a disorder related to the development of bone and cartilage, can also cause this disease.

text: During the Permian period synapsids, including the ancestors of mammals, may have dominated land environments, but the Permian–Triassic extinction event  came very close to wiping out complex life. The extinctions were apparently fairly sudden, at least among vertebrates. During the slow recovery from this catastrophe a previously obscure group, archosaurs, became the most abundant and diverse terrestrial vertebrates. One archosaur group, the dinosaurs, were the dominant land vertebrates for the rest of the Mesozoic, and birds evolved from one group of dinosaurs. During this time mammals' ancestors survived only as small, mainly nocturnal insectivores, but this apparent set-back may have accelerated the development of mammalian traits such as endothermy and hair. After the Cretaceous–Paleogene extinction event  killed off the non-avian dinosaurs – birds are the only surviving dinosaurs – mammals increased rapidly in size and diversity, and some took to the air and the sea.

text: During the

text: Permian

text: period

text: synapsid

text: s, including the ancestors of

text: mammal

text: s, may have dominated land environments, but the

text: Permian–Triassic extinction event

text: came very close to wiping out complex life. The extinctions were apparently fairly sudden, at least among vertebrates. During the slow recovery from this catastrophe a previously obscure group,

text: archosaur

text: s, became the most abundant and diverse terrestrial vertebrates. One archosaur group, the

text: dinosaur

text: s, were the dominant land vertebrates for the rest of the

text: Mesozoic

text: , and

text: bird

text: s evolved from one group of dinosaurs. During this time mammals' ancestors survived only as small, mainly nocturnal

text: insectivore

text: s, but this apparent set-back may have accelerated the development of mammalian traits such as

text: endothermy

text: and

text: hair

text: . After the

text: Cretaceous–Paleogene extinction event

text: killed off the non-avian dinosaurs – birds are the only surviving dinosaurs – mammals increased rapidly in size and diversity, and some took to the air and the sea.

text: Some of the terms commonly used to describe the condition include herniated disc, prolapsed disc, ruptured disc and slipped disc. Other phenomena that are closely related include disc protrusion, pinched nerves, sciatica, disc disease, disc degeneration, degenerative disc disease, and black disc. The popular term slipped disc is a misnomer, as the intervertebral discs are tightly sandwiched between two vertebrae to which they are attached, and cannot actually "slip", or even get out of place. The disc is actually grown together with the adjacent vertebrae and can be squeezed, stretched and twisted, all in small degrees. It can also be torn, ripped, herniated, and degenerated, but it cannot "slip". Some authors consider that the term "slipped disc" is harmful, as it leads to an incorrect idea of what has occurred and thus of the likely outcome. However, during growth, one vertebral body can slip relative to an adjacent vertebral body. This congenital deformity is called spondylolisthesis.

text: Some of the terms commonly used to describe the condition include herniated disc, prolapsed disc, ruptured disc and slipped disc. Other phenomena that are closely related include

text: disc protrusion

text: , pinched nerves,

text: sciatica

text: , disc disease, disc degeneration,

text: degenerative disc disease

text: , and black disc. The popular term slipped disc is a misnomer, as the intervertebral discs are tightly sandwiched between two

text: vertebrae

text: to which they are attached, and cannot actually "slip", or even get out of place. The disc is actually grown together with the adjacent vertebrae and can be squeezed, stretched and twisted, all in small degrees. It can also be torn, ripped, herniated, and degenerated, but it cannot "slip". Some authors consider that the term "slipped disc" is harmful, as it leads to an incorrect idea of what has occurred and thus of the likely outcome. However, during growth, one vertebral body can slip relative to an adjacent vertebral body. This congenital deformity is called

text: spondylolisthesis

text: Measuring diversity at one level in a group of organisms may not precisely correspond to diversity at other levels. However, tetrapod (terrestrial vertebrates) taxonomic and ecological diversity shows a very close correlation.

text: Measuring diversity at one level in a group of organisms may not precisely correspond to diversity at other levels. However,

text: tetrapod

text: (terrestrial

text: vertebrates

text: ) taxonomic and ecological diversity shows a very close correlation.

text: Fish reproduction

text: Fish reproduction

text: The amniotic egg represents a critical divergence within the vertebrates, one enabled to reproduce on dry land—free of the need to return to water for reproduction as required of the amphibians. From this point the amniotes spread around the globe, eventually to become the dominant land vertebrates. Very early in the evolutionary history of amniotes, basal amniotes diverged into two main lines, the synapsids and the sauropsids, both of which persist into the modern era. The oldest known fossil synapsid is Protoclepsydrops from about 312 million years ago, while the oldest known sauropsid is probably Paleothyris, in the order Captorhinida, from the Middle Pennsylvanian epoch (ca. 306–312 million years ago).

text: The amniotic egg represents a critical divergence within the vertebrates, one enabled to reproduce on dry land—free of the need to return to water for reproduction as required of the amphibians. From this point the amniotes spread around the globe, eventually to become the dominant land vertebrates. Very early in the evolutionary history of amniotes, basal amniotes

text: diverged into two main lines

text: , the

text: synapsid

text: s and the

text: sauropsid

text: s, both of which persist into the modern era. The oldest known fossil synapsid is

text: Protoclepsydrops

text: from about 312 million years ago, while the oldest known sauropsid is probably

text: Paleothyris

text: , in the order

text: Captorhinida

text: , from the

text: Middle Pennsylvanian

text: epoch (ca. 306–312 million years ago).

text: In fish, there are often two sets of ribs attached to the vertebral column. One set, the dorsal ribs, are found in the dividing septum between the upper and lower parts of the main muscle segments, projecting roughly sideways from the vertebral column. The second set, of ventral ribs arise from the vertebral column just below the dorsal ribs, and enclose the lower body, often joining at the tips. Not all species possess both types of rib, with the dorsal ribs being most commonly absent. Sharks, for example, have no dorsal ribs, and only very short ventral ribs, while lampreys have no ribs at all. In some teleosts, there may be additional rib-like bones within the muscle mass.

text: In

text: fish

text: , there are often two sets of ribs attached to the vertebral column. One set, the dorsal ribs, are found in the dividing septum between the upper and lower parts of the main muscle segments, projecting roughly sideways from the vertebral column. The second set, of ventral ribs arise from the vertebral column just below the dorsal ribs, and enclose the lower body, often joining at the tips. Not all species possess both types of rib, with the dorsal ribs being most commonly absent.

text: Shark

text: s, for example, have no dorsal ribs, and only very short ventral ribs, while

text: lamprey

text: s have no ribs at all. In some

text: teleost

text: s, there may be additional rib-like bones within the muscle mass.

text: Vertebral fractures, while having a smaller impact on mortality, can lead to a severe chronic pain of neurogenic origin, which can be hard to control, as well as deformity. Though rare, multiple vertebral fractures can lead to such severe hunch back (kyphosis), the resulting pressure on internal organs can impair one's ability to breathe.

text: Vertebral fractures, while having a smaller impact on mortality, can lead to a severe chronic pain of neurogenic origin, which can be hard to control, as well as deformity. Though rare, multiple vertebral fractures can lead to such severe hunch back (

text: kyphosis

text: ), the resulting pressure on internal organs can impair one's ability to breathe.

text: In adults, surgery to detether (free) the spinal cord can reduce the size and further development of cysts in the cord and may restore some function or alleviate other symptoms. Although detethering is the common surgical approach to TCS, another surgical option for adults is a spine-shortening vertebral osteotomy. A vertebral osteotomy aims to indirectly relieve the excess tension on the spinal cord by removing a portion of the spine, shortening it. This procedure offers a unique benefit in that the spinal cord remains fixated to the spine, preventing retethering and spinal cord injury as possible surgical complications. However, its complexity and limited “track record” presently keeps vertebral osteotomies reserved as an option for patients who have failed in preventing retethering after detethering procedure(s).

text: In adults, surgery to detether (free) the spinal cord can reduce the size and further development of cysts in the cord and may restore some function or alleviate other symptoms. Although detethering is the common surgical approach to TCS, another surgical option for adults is a spine-shortening vertebral

text: osteotomy

text: . A vertebral osteotomy aims to indirectly relieve the excess tension on the spinal cord by removing a portion of the spine, shortening it. This procedure offers a unique benefit in that the spinal cord remains fixated to the spine, preventing retethering and spinal cord injury as possible surgical complications. However, its complexity and limited “track record” presently keeps vertebral osteotomies reserved as an option for patients who have failed in preventing retethering after detethering procedure(s).

text: Vertebrate animals such as tropical fish and birds sometimes have more complex color vision systems than humans; thus the many subtle colors they exhibit generally serve as direct signals for other fish or birds, and not to signal mammals. In bird vision, tetrachromacy is achieved through up to four cone types, depending on species. Each single cone contains one of the four main types of vertebrate cone photopigment (LWS/ MWS, RH2, SWS2 and SWS1) and has a colored oil droplet in its inner segment. Brightly colored oil droplets inside the cones shift or narrow the spectral sensitivity of the cell. It has been suggested that it is likely that pigeons are pentachromats.

text: Vertebrate animals such as

text: tropical fish

text: and birds sometimes have more complex color vision systems than humans; thus the many subtle colors they exhibit generally serve as direct signals for other fish or birds, and not to signal mammals. In

text: bird vision

text: tetrachromacy

text: is achieved through up to four

text: cone

text: types, depending on species. Each single cone contains one of the four main types of vertebrate cone

text: photopigment

text: (LWS/ MWS, RH2, SWS2 and SWS1) and has a colored

text: oil droplet

text: in its inner segment. Brightly colored oil droplets inside the cones shift or narrow the spectral sensitivity of the cell. It has been suggested that it is likely that

text: pigeon

text: s are

text: pentachromat

text: s.

text: In 2015, three traits were added. The shoulder blade is robust and large, fused with the coracoid. The vertebral centra of the front tail vertebrae are shorter and especially taller. With the tail vertebrae, the base of the side process covers the top half of the centrum, seen from the front or from behind, instead of a quarter of the height.

text: Because ectotherms depend on environmental conditions for body temperature regulation, they typically are more sluggish at night and in the morning when they emerge from their shelters to heat up in the first sunlight. Foraging activity is therefore restricted to the day time (diurnal activity patterns) in most vertebrate ectotherms. In lizards, for instance, only a few species are known to be nocturnal (e.g. many geckos) and they mostly use 'sit and wait' foraging strategies that may not require body temperatures as high as those necessary for active foraging. Endothermic vertebrate species are therefore less dependent on the environmental conditions and have developed a high variability (both within and between species) in their diurnal activity patterns.

text: The choice of the sub-periosteum site is used because stimulation of the cambium layer using transforming growth factor–beta resulted in enhanced chondrogenesis, i.e., formation of cartilage. In development the formation of bone can either occur via a Cartilage template initially formed by the MSCs that then gets ossified through a process called endochondral ossification or directly from MSC differentiation to bone via a process termed intra-membranous ossification.  Upon exposure of the periosteal cells to calcium from the alginate gel, these cells become bone cells and start producing bone matrix through the intra-membranous ossification process, recapitulating all steps of bone matrix deposition.  The extension of the IVB paradigm to engineering autologous hyaline cartilage was also recently demonstrated.  In this case, agarose is injected and this triggers local hypoxia, which then results in the differentiation of the periosteal MSCs into articular chondrocytes, i.e. cells similar to those found in the joint cartilage. Since this processes occurs in a relative short period of less than two weeks and cartilage can remodel into bone, this approach might provide some advantages in treatment of both cartilage and bone loss. The IVB concept needs to be however realized in humans and this is currently being undertaken.

text: The choice of the sub-periosteum site is used because stimulation of the cambium layer using transforming growth factor–beta resulted in enhanced

text: chondrogenesis

text: , i.e., formation of

text: cartilage

text: . In development the formation of bone can either occur via a Cartilage template initially formed by the MSCs that then gets ossified through a process called

text: endochondral ossification

text: or directly from MSC

text: differentiation

text: to bone via a process termed

text: intra-membranous ossification

text: .  Upon exposure of the periosteal cells to calcium from the alginate gel, these cells become bone cells and start producing bone matrix through the intra-membranous ossification process, recapitulating all steps of bone matrix deposition.  The extension of the IVB paradigm to engineering autologous

text: hyaline

text: cartilage was also recently demonstrated.  In this case,

text: agarose

text: is injected and this triggers local

text: hypoxia

text: , which then results in the differentiation of the periosteal MSCs into articular chondrocytes, i.e. cells similar to those found in the joint cartilage. Since this processes occurs in a relative short period of less than two weeks and cartilage can remodel into bone, this approach might provide some advantages in treatment of both cartilage and bone loss. The IVB concept needs to be however realized in humans and this is currently being undertaken.

text: It took many millions of years for vertebrates to transition out of water onto land. During this time, both the competitive pressures that would push species out of the water and the  niche occupation incentives that would pull species onto land were slowly building. The culmination of these driving factors are what ultimately facilitated the vertebrate transition.

text: It took many millions of years for vertebrates to transition out of water onto land. During this time, both the competitive pressures that would push species out of the water and the

text: niche

text: occupation incentives that would pull species onto land were slowly building. The culmination of these driving factors are what ultimately facilitated the vertebrate transition.

text: The Tetrapodomorpha (also known as Choanata) are a clade of vertebrates consisting of tetrapods (four-limbed vertebrates) and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish. Advanced forms transitional between fish and the early labyrinthodonts, such as Tiktaalik, have been referred to as "fishapods" by their discoverers, being half-fish, half-tetrapods, in appearance and limb morphology. The Tetrapodomorpha contains the crown group tetrapods (the last common ancestor of living tetrapods and all of its descendants) and several groups of early stem tetrapods, and  several groups of related lobe-finned fishes, collectively known as the osteolepiforms. The Tetrapodamorpha minus the crown group Tetrapoda are the Stem Tetrapoda, a paraphyletic unit encompassing the fish to tetrapod transition.

text: The Tetrapodomorpha (also known as Choanata) are a

text: clade

text: of

text: vertebrate

text: s consisting of

text: tetrapod

text: s (four-limbed vertebrates) and their closest

text: sarcopterygian

text: relatives that are more closely related to living tetrapods than to living

text: lungfish

text: . Advanced forms transitional between fish and the early

text: labyrinthodont

text: s, such as

text: Tiktaalik

text: , have been referred to as "fishapods" by their discoverers, being half-fish, half-tetrapods, in appearance and limb morphology. The Tetrapodomorpha contains the

text: crown group

text: tetrapods (the last common ancestor of living tetrapods and all of its descendants) and several groups of early

text: stem tetrapod

text: s, and  several groups of related lobe-finned fishes, collectively known as the

text: osteolepiform

text: s. The Tetrapodamorpha minus the

text: crown group

text: Tetrapoda are the

text: Stem Tetrapoda

text: , a

text: paraphyletic

text: unit encompassing the fish to tetrapod transition.

text: The formation contains a diverse array of vertebrate and invertebrate fossils. About 70% of the macrofossils are osteichthyan fish.  Other vertebrates include chelonians, pterosaurs, lepidosaurs, and crocodiles.  Cyanobacteria, foraminifera, algae, gymnosperms, sponges, cnidarians, annelids, gastropods, ammonites, bivalves, arachnids, insects, isopods, anomurans, brachyurans, crinoids, echinoids, holothuroids, stelleroids, and ophiuroids,have also been recovered from the Tlayúa Formation.

text: The formation contains a diverse array of

text: vertebrate

text: and

text: invertebrate

text: fossil

text: s. About 70% of the

text: macrofossil

text: s are

text: osteichthyan

text: fish.  Other vertebrates include

text: chelonians

text: pterosaur

text: s,

text: lepidosaurs

text: , and

text: crocodile

text: s.

text: Cyanobacteria

text: foraminifera

text: algae

text: gymnosperm

text: s,

text: sponge

text: s,

text: cnidarians

text: annelid

text: s,

text: gastropod

text: s,

text: ammonite

text: s,

text: bivalves

text: arachnid

text: s,

text: insect

text: s,

text: isopods

text: anomuran

text: s,

text: brachyura

text: ns,

text: crinoid

text: s,

text: echinoid

text: s,

text: holothuroids

text: stelleroids

text: , and

text: ophiuroids

text: ,have also been recovered from the Tlayúa Formation.

text: Tiktaalik is a transitional fossil; it is to tetrapods what Aurornis is to birds, troodonts and dromaeosaurids. While it may be that neither is ancestor to any living animal, they serve as evidence that intermediates between very different types of vertebrates did once exist. The mixture of both fish and tetrapod characteristics found in Tiktaalik include these traits:

text: Tiktaalik is a

text: transitional fossil

text: ; it is to tetrapods what

text: Aurornis

text: is to

text: birds

text: troodonts

text: and

text: dromaeosaurids

text: . While it may be that neither is ancestor to any living animal, they serve as evidence that intermediates between very different types of vertebrates did once exist. The mixture of both fish and tetrapod characteristics found in Tiktaalik include these traits:

text: Finally, the cartilaginous fish, such as sharks, do not have any of the bones found in the lower jaw of other vertebrates. Instead, their lower jaw is composed of a cartilagenous structure homologous with the Meckel's cartilage of other groups. This also remains a significant element of the jaw in some primitive bony fish, such as sturgeons.

text: Finally, the

text: cartilaginous fish

text: , such as

text: shark

text: s, do not have any of the bones found in the lower jaw of other vertebrates. Instead, their lower jaw is composed of a

text: cartilage

text: nous structure homologous with the

text: Meckel's cartilage

text: of other groups. This also remains a significant element of the jaw in some primitive bony fish, such as

text: sturgeon

text: s.

text: The bodies in the middle of the thoracic region are heart-shaped, and as broad in the antero-posterior as in the transverse direction. At the ends of the thoracic region they resemble respectively those of the cervical and lumbar vertebrae. They are slightly thicker behind than in front, flat above and below, convex from side to side in front, deeply concave behind, and slightly constricted laterally and in front. They present, on either side, two costal demi-facets, one above, near the root of the pedicle, the other below, in front of the inferior vertebral notch; these are covered with cartilage in the fresh state, and, when the vertebrae are articulated with one another, form, with the intervening intervertebral fibrocartilages, oval surfaces for the reception of the heads of the ribs.

text: The

text: bodies

text: in the middle of the thoracic region are heart-shaped, and as broad in the antero-posterior as in the transverse direction. At the ends of the thoracic region they resemble respectively those of the cervical and lumbar vertebrae. They are slightly thicker behind than in front, flat above and below, convex from side to side in front, deeply concave behind, and slightly constricted laterally and in front. They present, on either side, two costal demi-facets, one above, near the root of the pedicle, the other below, in front of the inferior vertebral notch; these are covered with cartilage in the fresh state, and, when the vertebrae are articulated with one another, form, with the intervening intervertebral fibrocartilages, oval surfaces for the reception of the heads of the ribs.

text: The lumbosacral joint is a joint of the body, between the last lumbar vertebra and the first sacral segment of the vertebral column. In some ways, calling it a "joint" (singular) is a misnomer, since the lumbosacral junction includes a disc between the lower lumbar vertebral body and the uppermost sacral vertebral body, as well as two lumbosacral facet joints (right and left zygapophysial joints).

text: The lumbosacral joint is a joint of the body, between the last

text: lumbar vertebra

text: and the first

text: sacral segment

text: of the

text: vertebral column

text: . In some ways, calling it a "joint" (singular) is a misnomer, since the lumbosacral junction includes a disc between the lower lumbar vertebral body and the uppermost sacral vertebral body, as well as two lumbosacral facet joints (right and left

text: zygapophysial joint

text: s).

text: Hagfish form a class of about 20 species of eel-shaped, slime-producing marine fish. They are the only known living animals that have a skull but no vertebral column. Lampreys form a superclass containing 38 known extant species of jawless fish. The adult lamprey is be characterized by a toothed, funnel-like sucking mouth. Although they are well known for boring into the flesh of other fish to suck their blood, only 18 species of lampreys are actually parasitic. Together hagfish and lampreys are the sister group to vertebrates. Living hagfish remain similar to hagfish from around 300 million years ago. The lampreys are a very ancient lineage of vertebrates, though their exact relationship to hagfishes and jawed vertebrates is still a matter of dispute.

text: Hagfish

text: form a class of about 20 species of

text: eel

text: -shaped,

text: slime

text: -producing marine fish. They are the only known living animals that have a

text: skull

text: but no

text: vertebral column

text: Lamprey

text: s form a superclass containing 38 known extant species of

text: jawless fish

text: . The adult lamprey is be characterized by a toothed, funnel-like sucking mouth. Although they are well known for boring into the flesh of other fish to

text: suck their blood

text: , only 18 species of lampreys are actually parasitic. Together hagfish and lampreys are the sister group to vertebrates. Living hagfish remain similar to hagfish from around 300 million years ago. The lampreys are a very ancient lineage of vertebrates, though their exact relationship to

text: hagfish

text: es and

text: jawed vertebrate

text: s is still a matter of dispute.

text: Like all Plasmodium species P. guyannense has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. guyannense has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: The vertebral column, parts of which are among the only articulated elements of the skeleton, is nevertheless too incompletely preserved for an exact vertebrae number to be estimated. Its original describer, Florian Heller, counted seven cervicals and five presumably fused sacrals. The left scapula, while badly damaged proximally, is in good condition distally; the right scapula is partly articulated with the coracoid at an almost right angle. The furcula is relatively well preserved, sitting close to its natural position and showing typical boomerang shape. All three components of the pelvic girdle—illium, ischium and publs—are somewhat articulated in almost natural position.

text: The vertebral column usually contains 54 bones: 7 cervical vertebrae, including the atlas (C1) and axis (C2) which support and help move the skull, 18 (or rarely, 19) thoracic,  5-6 lumbar, 5 sacral (which fuse together to form the sacrum), and 15-25 caudal vertebrae with an average of 18. Differences in number may occur, particularly in certain breeds.  For example, some, though not all, Arabians, may have 5 lumbar vertebrae, opposed to the usual 6, 17 thoracic vertebrae (and ribs) instead of 18, and 16 or 17 caudal vertebrae instead of 18. The withers of the horse are made up by the dorsal spinal processes of the thoracic vertebrae numbers 5 to 9.

text: The vertebral column usually contains 54 bones: 7 cervical vertebrae, including the

text: atlas

text: (C1) and axis (C2) which support and help move the skull, 18 (or rarely, 19) thoracic,  5-6 lumbar, 5 sacral (which fuse together to form the sacrum), and 15-25 caudal vertebrae with an average of 18. Differences in number may occur, particularly in certain breeds.  For example, some, though not all,

text: Arabians

text: , may have 5 lumbar vertebrae, opposed to the usual 6, 17 thoracic vertebrae (and ribs) instead of 18, and 16 or 17 caudal vertebrae instead of 18. The

text: withers

text: of the horse are made up by the dorsal spinal processes of the thoracic vertebrae numbers 5 to 9.

text: The CNS of chordates differs from that of other animals in being placed dorsally in the body, above the gut and notochord/spine. The basic pattern of the CNS is highly conserved throughout the different species of vertebrates and during evolution. The major trend that can be observed is towards a progressive telencephalisation: the telencephalon of reptiles is only an appendix to the large olfactory bulb, while in mammals it makes up most of the volume of the CNS. In the human brain, the telencephalon covers most of the diencephalon and the mesencephalon. Indeed, the allometric study of brain size among different species shows a striking continuity from rats to whales, and allows us to complete the knowledge about the evolution of the CNS obtained through cranial endocasts.

text: The CNS of

text: chordate

text: s differs from that of other animals in being placed dorsally in the body, above the gut and

text: notochord

text: spine

text: . The basic pattern of the CNS is highly conserved throughout the different species of

text: vertebrate

text: s and during evolution. The major trend that can be observed is towards a progressive telencephalisation: the

text: telencephalon

text: of reptiles is only an appendix to the large

text: olfactory bulb

text: , while in mammals it makes up most of the volume of the CNS. In the human brain, the telencephalon covers most of the

text: diencephalon

text: and the

text: mesencephalon

text: . Indeed, the

text: allometric

text: study of brain size among different species shows a striking continuity from rats to whales, and allows us to complete the knowledge about the evolution of the CNS obtained through

text: cranial endocast

text: s.

text: They are internal parasites of molluscs and vertebrates. Most trematodes have a complex life cycle with at least two hosts. The primary host, where the flukes sexually reproduce, is a vertebrate. The intermediate host, in which asexual reproduction occurs, is usually a snail.

text: They are internal

text: parasites

text: of

text: molluscs

text: and

text: vertebrates

text: . Most trematodes have a complex

text: life cycle

text: with at least two hosts. The primary host, where the flukes sexually reproduce, is a vertebrate. The intermediate host, in which

text: asexual reproduction

text: occurs, is usually a

text: snail

text: Leatherbacks have been viewed as unique among extant reptiles for their ability to maintain high body temperatures using metabolically generated heat, or endothermy. Initial studies on their metabolic rates found leatherbacks had resting metabolisms around three times higher than expected for reptiles of their size. However, recent studies using reptile representatives encompassing all the size ranges leatherbacks pass through during ontogeny discovered the resting metabolic rate of a large D. coriacea is not significantly different from predicted results based on allometry.

text: Leatherbacks have been viewed as unique among extant reptiles for their ability to maintain high body temperatures using

text: metabolically

text: generated heat, or

text: endothermy

text: . Initial studies on their metabolic rates found leatherbacks had resting metabolisms around three times higher than expected for reptiles of their size. However, recent studies using reptile representatives encompassing all the size ranges leatherbacks pass through during

text: ontogeny

text: discovered the resting metabolic rate of a large D. coriacea is not significantly different from predicted results based on

text: allometry

text: The paleofauna of the Horseshoe Canyon Formation featured a number of vertebrates that lived at the same time as Montanoceratops.  This included dinosaurs such as the ankylosaurids Anodontosaurus lambei, Edmontonia longiceps, Euoplocephalus tutus, the maniraptorans Atrociraptor marshalli, Epichirostenotes curriei, Richardoestesia gilmorei, Richardoestesia isosceles, the troodontid Paronychodon lacustris and an unnamed species of Troodon, the alvarezsaurid theropod Albertonykus borealis, the ornithomimids Dromiceiomimus brevitertius, Ornithomimus edmontonicus, and an unnamed species of Struthiomimus, the bone-head pachycephalosaurid Stegoceras, and Sphaerotholus edmontonensis, the ornithopod Parksosaurus warreni, the hadrosaurids Edmontosaurus regalis, Hypacrosaurus altispinus, and Saurolophus osborni,  the ceratopsians Anchiceratops ornatus, Arrhinoceratops brachyops, Eotriceratops xerinsularis, Pachyrhinosaurus canadensis and Pachyrhinosaurus lakustai, the primitive tyrannosauroid Dryptosaurus, and the tyrannosaurids Albertosaurus and Daspletosaurus, which were the apex predators of this paleoenvironment.  Of these, the hadrosaurs dominated in terms of shear number and made up half of all dinosaurs who lived in this region.  Vertebrates present in the Horseshoe Canyon Formation at the time of Montanoceratops included reptiles, and amphibians.  Sharks, rays, sturgeons, bowfins, gars and the gar-like Aspidorhynchus made up the fish fauna.  Reptiles such as turtles and crocodilians are rare in the Horseshoe Canyon Formation, and this was thought to reflect the relatively cool climate which prevailed at the time.  A study by Quinney et al. (2013) however, showed that the decline in turtle diversity, which was previously attributed to climate, coincided instead with changes in soil drainage conditions, and was limited by aridity, landscape instability, and migratory barriers.  The saltwater plesiosaur Leurospondylus was present and freshwater environments were populated by turtles, Champsosaurus, and crocodilians like Leidyosuchus and Stangerochampsa.  Evidence has shown that multituberculates and the early marsupial Didelphodon coyi were present.  Vertebrate trace fossils from this region included the tracks of theropods, ceratopsians and ornithopods, which provide evidence that these animals were also present.  Non-vertebrates in this ecosystem included both marine and terrestrial invertebrates.

text: The paleofauna of the Horseshoe Canyon Formation featured a number of vertebrates that lived at the same time as Montanoceratops.  This included dinosaurs such as the

text: ankylosaurids

text: Anodontosaurus

text: lambei,

text: Edmontonia

text: longiceps,

text: Euoplocephalus

text: tutus, the

text: maniraptoran

text: s

text: Atrociraptor

text: marshalli,

text: Epichirostenotes

text: curriei,

text: Richardoestesia

text: gilmorei,

text: Richardoestesia

text: isosceles, the

text: troodontid

text: Paronychodon

text: lacustris and an unnamed species of

text: Troodon

text: , the

text: alvarezsaurid

text: theropod

text: Albertonykus

text: borealis, the

text: ornithomimids

text: Dromiceiomimus

text: brevitertius,

text: Ornithomimus

text: edmontonicus, and an unnamed species of

text: Struthiomimus

text: , the

text: bone-head pachycephalosaurid

text: Stegoceras

text: , and

text: Sphaerotholus

text: edmontonensis, the

text: ornithopod

text: Parksosaurus

text: warreni, the

text: hadrosaurids

text: Edmontosaurus

text: regalis,

text: Hypacrosaurus

text: altispinus, and

text: Saurolophus

text: osborni,  the

text: ceratopsians

text: Anchiceratops

text: ornatus,

text: Arrhinoceratops

text: brachyops,

text: Eotriceratops

text: xerinsularis,

text: Pachyrhinosaurus

text: canadensis and

text: Pachyrhinosaurus

text: lakustai, the primitive

text: tyrannosauroid

text: Dryptosaurus

text: , and the

text: tyrannosaurids

text: Albertosaurus

text: and

text: Daspletosaurus

text: , which were the

text: apex predators

text: of this paleoenvironment.  Of these, the hadrosaurs dominated in terms of shear number and made up half of all dinosaurs who lived in this region.  Vertebrates present in the Horseshoe Canyon Formation at the time of Montanoceratops included

text: reptile

text: s, and

text: amphibian

text: s.

text: Shark

text: s,

text: rays

text: sturgeon

text: s,

text: bowfin

text: s,

text: gar

text: s and the gar-like

text: Aspidorhynchus

text: made up the fish fauna.  Reptiles such as turtles and crocodilians are rare in the Horseshoe Canyon Formation, and this was thought to reflect the relatively cool climate which prevailed at the time.  A study by Quinney et al. (2013) however, showed that the decline in turtle diversity, which was previously attributed to climate, coincided instead with changes in soil drainage conditions, and was limited by aridity, landscape instability, and migratory barriers.  The saltwater

text: plesiosaur

text: Leurospondylus

text: was present and freshwater environments were populated by

text: turtle

text: s,

text: Champsosaurus

text: , and

text: crocodilia

text: ns like

text: Leidyosuchus

text: and

text: Stangerochampsa

text: .  Evidence has shown that

text: multituberculate

text: s and the early

text: marsupial

text: Didelphodon

text: coyi were present.  Vertebrate trace fossils from this region included the tracks of

text: theropods

text: ceratopsians

text: and

text: ornithopods

text: , which provide evidence that these animals were also present.  Non-vertebrates in this ecosystem included both marine and terrestrial

text: invertebrate

text: s.

text: Evolution of the head In the vertebrates has occurred by the fusion of a fixed number of anterior segments, in the same manner as in other ”heteronomously segmented animals”. In some cases segments or a portion of the segments disappear. The head segments also lose most of its systems except for  the nervous system. With the progressive development of cephalization, "the head incorporates more and more of the adjacent segments into its structure, so that in general it may be said that the higher the degree of cepahalization the greater is the number of segments composing the head".

text: Evolution of the head In the

text: vertebrates

text: has occurred by the fusion of a fixed number of anterior segments, in the same manner as in other ”heteronomously segmented animals”. In some cases segments or a portion of the segments disappear. The head segments also lose most of its systems except for  the nervous system. With the progressive development of

text: cephalization

text: , "the head incorporates more and more of the adjacent segments into its structure, so that in general it may be said that the higher the degree of cepahalization the greater is the number of segments composing the head".

text: There are many examples of exaptations. A classic example is how feathers, which initially evolved for heat regulation, were co-opted for display, and later co-opted for use in bird flight. Another example is the lungs of many basal fish, which evolved into the lungs of terrestrial vertebrates but also underwent exaptation to become the gas bladder, a buoyancy control organ, in derived fish.

text: There are many examples of exaptations. A classic example is how

text: feathers

text: , which initially evolved for heat regulation, were co-opted for display, and later co-opted for use in bird flight. Another example is the lungs of many basal fish, which evolved into the lungs of terrestrial vertebrates but also underwent exaptation to become the

text: gas bladder

text: , a buoyancy control organ, in derived fish.

text: Osteoporosis is a major health problem. Fractures of the spine or vertebral fractures occur commonly in men and women over the age of 60 and hip fracture remains a leading cause of death in elderly individuals. Repair and rehabilitation of hip fractures currently cost 15 billion dollars per year; as the "baby boomers" enter their 70s (2020) this figure is expected to reach 40-60 billion dollars per year unless effective therapies are developed. Although the introduction of several new therapies have reduced the incidence of fracture by as much as 5-10%, low bone mass leading to fractures remains a major health issue. The Surgeon General's report on osteoporosis, issued in 2004, estimates "One out of every two women over 50 will have an osteoporosis-related fracture in their lifetime, with risk of fracture increasing with age. Due primarily to the aging of the population and the previous lack of focus on bone health, the number of hip fractures in the United States could double or even triple by the year 2020."

text: Osteoporosis

text: is a major health problem. Fractures of the

text: spine

text: or

text: vertebral

text: fractures occur commonly in men and women over the age of 60 and

text: hip

text: fracture remains a leading cause of death in elderly individuals.

text: Repair and rehabilitation

text: of

text: hip fracture

text: s currently cost 15 billion dollars per year; as the "

text: baby boomer

text: s" enter their 70s (2020) this figure is expected to reach 40-60 billion dollars per year unless effective therapies are developed. Although the introduction of several new therapies have reduced the incidence of fracture by as much as 5-10%, low bone mass leading to fractures remains a major health issue. The

text: Surgeon General

text: 's report on osteoporosis, issued in 2004, estimates "One out of every two women over 50 will have an osteoporosis-related

text: fracture

text: in their lifetime, with risk of fracture increasing with age. Due primarily to the aging of the population and the previous lack of focus on bone health, the number of hip fractures in the United States could double or even triple by the year 2020."

text: In 1879, the article entitled "Note sur la circulation veineuse du cerveau et sur le mode de développement des corpuscules de Pacchioni" was published in the "Archives de Physiologie Normale et Pathologique" (currently known as the Journal of Physiology [Paris]). In a short introduction to this publication, Labbé mentioned that Paul Jules Tillaux (1834–1904) was his supervisor. Tillaux was a famous surgeon, also working at the Beaujon Hospital, who produced publications about the surgical treatment of fractures of the vertebral column, among other subjects. In the body of the article, Labbé described various kinds of intracranial connections of cerebral veins. In his paragraph on the communications between dural sinuses, he reported the presence of the vein that bears his name.

text: In 1879, the article entitled "Note sur la circulation veineuse du cerveau et sur le mode de développement des corpuscules de Pacchioni" was published in the "Archives de Physiologie Normale et Pathologique" (currently known as the Journal of Physiology [Paris]). In a short introduction to this publication, Labbé mentioned that

text: Paul Jules Tillaux

text: (1834–1904) was his supervisor. Tillaux was a famous surgeon, also working at the

text: Beaujon Hospital

text: , who produced publications about the surgical treatment of fractures of the

text: vertebral column

text: , among other subjects. In the body of the article, Labbé described various kinds of intracranial connections of

text: cerebral veins

text: . In his paragraph on the communications between

text: dural sinuses

text: , he reported the presence of the vein that bears his name.

text: As previously mentioned, Hox genes encode transcription factors that regulate embryonic and post-embryonic developmental processes.<ref name='Voss 2013'>Voss, S. R., Putta, S., Walker, J. A., Smith, J. J., Maki, N., & Tsonis, P. A. (2013). "Salamander Hox clusters contain repetitive DNA and expanded non-coding regions: a typical Hox structure for non-mammalian tetrapod vertebrates?" Hum Genomics, 7(9).</ref>  The expression of Hox genes is regulated in part by the tight, spatial arrangement of conserved coding and non-coding DNA regions.<ref name='Voss 2013'/> The potential for evolutionary alterations in Hox cluster composition is viewed to be small among vertebrates. On the other hand, recent studies of a small number of non-mammalian taxa propose greater dissimilarity than initially considered.<ref name='Voss 2013'/> Next, generation sequencing of considerable genomic fragments greater than 100 kilobases from the eastern newt (Notophthalmus viridescens) was analyzed. Subsequently, it was found that the composition of Hox cluster genes were conserved relative to orthologous regions from other vertebrates. Furthermore, it was found that the length of introns and intergenic regions varied.<ref name='Voss 2013'/> In particular, the distance between HoxD13 and HoxD11 is longer in newt than orthologous regions from vertebrate species with expanded Hox clusters and is predicted to exceed the length of the entire HoxD clusters (HoxD13–HoxD4) of humans, mice, and frogs.<ref name='Voss 2013'/> Many recurring DNA sequences were recognized for newt Hox clusters, counting an enrichment of DNA transposon-like sequences similar to non-coding genomic fragments. Researchers found the results to suggest that Hox cluster expansion and transposon accumulation are common features of non-mammalian tetrapod vertebrates.<ref name='Voss 2013'/>

text: As previously mentioned, Hox genes encode

text: transcription factor

text: s that regulate embryonic and post-embryonic developmental processes.<ref name='Voss 2013'>Voss, S. R., Putta, S., Walker, J. A., Smith, J. J., Maki, N., & Tsonis, P. A. (2013). "Salamander Hox clusters contain repetitive DNA and expanded non-coding regions: a typical Hox structure for non-mammalian tetrapod vertebrates?" Hum Genomics, 7(9).</ref>  The expression of Hox genes is regulated in part by the tight, spatial arrangement of conserved

text: coding

text: and

text: non-coding

text: DNA regions.<ref name='Voss 2013'/> The potential for evolutionary alterations in Hox cluster composition is viewed to be small among vertebrates. On the other hand, recent studies of a small number of non-mammalian

text: taxa

text: propose greater dissimilarity than initially considered.<ref name='Voss 2013'/> Next, generation sequencing of considerable genomic fragments greater than 100 kilobases from the

text: eastern newt

text: (Notophthalmus viridescens) was analyzed. Subsequently, it was found that the composition of Hox cluster genes were conserved relative to orthologous regions from other vertebrates. Furthermore, it was found that the length of

text: intron

text: s and

text: intergenic region

text: s varied.<ref name='Voss 2013'/> In particular, the distance between HoxD13 and HoxD11 is longer in newt than orthologous regions from vertebrate species with expanded Hox clusters and is predicted to exceed the length of the entire HoxD clusters (HoxD13–HoxD4) of humans, mice, and frogs.<ref name='Voss 2013'/> Many recurring DNA sequences were recognized for newt Hox clusters, counting an enrichment of DNA transposon-like sequences similar to non-coding genomic fragments. Researchers found the results to suggest that Hox cluster expansion and

text: transposon

text: accumulation are common features of non-mammalian tetrapod vertebrates.<ref name='Voss 2013'/>

text: The central nervous system of vertebrates is based on a hollow nerve cord running along the length of the animal. Of particular importance and unique to vertebrates is the presence of neural crest cells. These are progenitors of stem cells, and critical to coordinating the functions of cellular components. Neural crest cells migrate through the body from the nerve cord during development, and initiate the formation of neural ganglia and structures such as the jaws and skull.

text: The

text: central nervous system

text: of vertebrates is based on a hollow

text: nerve cord

text: running along the length of the animal. Of particular importance and unique to vertebrates is the presence of

text: neural crest

text: cells. These are progenitors of

text: stem cell

text: s, and critical to coordinating the functions of cellular components. Neural crest cells migrate through the body from the

text: nerve cord

text: during development, and initiate the formation of

text: neural ganglia

text: and structures such as the jaws and skull.

text: The first and second editions (1955 and 1969) provide an overview of the entire range of vertebrate evolution, and are illustrated by the distinctive drawings of Lois Darling.<ref>{{cite journal|title=Colbert’s Evolution of the Vertebrates. A History of the Backboned Animals Through Time|journal=Journal of Mammalogy|date=1 August 2003|volume=84|issue=3|pages=1121–1122|doi=10.1644/1545-1542(2003)084

text: The fossil record has been studied to try to clarify the relationship animals have to their environment, in part to help understand the current state of biodiversity. A close link has been found between vertebrate taxonomic and ecological diversity, that is, the diversity of animals and the niches they occupy.

text: The fossil record has been studied to try to clarify the relationship animals have to their environment, in part to help understand the current state of

text: biodiversity

text: . A close link has been found between vertebrate taxonomic and ecological diversity, that is, the diversity of animals and the

text: niche

text: s they occupy.

text: All of Oken's writings are deductive illustrations of an assumed principle, which, with other philosophers of the transcendental school, he deemed equal to the explanation of all the mysteries of nature. According to him, the head was a repetition of the trunk—a kind of second trunk, with its limbs and other appendages; this sum of his observations and comparisons—few of which he ever gave in detail—ought always to be borne in mind in comparing the share taken by Oken in homological anatomy with the progress made by other cultivators of that philosophical branch of the science.  The idea of the analogy between the skull, or parts of the skull, and the vertebral column had been previously propounded and ventilated in their lectures by Johann von Autenrieth (1772–1835) and Carl Kielmeyer (1765–1844), and in the writings of Johann Frank (1745–1821). By Oken it was applied chiefly in illustration of the mystical system of Schelling—the "all-in-all" and "all-in-every-part." From the earliest to the latest of Oken's writings on the subject, "the head is a repetition of the whole trunk with all its systems: the brain is the spinal cord; the cranium is the vertebral column; the mouth is intestine and abdomen; the nose is the lungs and thorax; the jaws are the limbs; and the teeth the claws or nails." Johann von Spix (1781–1826) in his folio Cephalogenesis (1818), richly illustrated comparative craniology, but presented the facts under the same transcendental guise; and Georges Cuvier (1769–1832) availed himself of the extravagances of these disciples of Schelling to cast ridicule on the whole inquiry into those higher relations of parts to the archetype which Sir Richard Owen (1804–1892) called "general homologies."

text: All of Oken's writings are deductive illustrations of an assumed principle, which, with other philosophers of the transcendental school, he deemed equal to the explanation of all the mysteries of nature. According to him, the head was a repetition of the trunk—a kind of second trunk, with its limbs and other appendages; this sum of his observations and comparisons—few of which he ever gave in detail—ought always to be borne in mind in comparing the share taken by Oken in

text: homological

text: anatomy with the progress made by other cultivators of that philosophical branch of the science.  The idea of the analogy between the skull, or parts of the skull, and the vertebral column had been previously propounded and ventilated in their lectures by

entity_name: Johann Heinrich Ferdinand von Autenrieth

text: Johann von Autenrieth

text: (1772–1835) and

text: Carl Kielmeyer

text: (1765–1844), and in the writings of

text: Johann Frank

text: (1745–1821). By Oken it was applied chiefly in illustration of the mystical system of Schelling—the "all-in-all" and "all-in-every-part." From the earliest to the latest of Oken's writings on the subject, "the head is a repetition of the whole trunk with all its systems: the brain is the spinal cord; the cranium is the vertebral column; the mouth is intestine and abdomen; the nose is the lungs and thorax; the jaws are the limbs; and the teeth the claws or nails."

text: Johann von Spix

text: (1781–1826) in his folio Cephalogenesis (1818), richly illustrated comparative

text: craniology

text: , but presented the facts under the same transcendental guise; and

text: Georges Cuvier

text: (1769–1832) availed himself of the extravagances of these disciples of Schelling to cast ridicule on the whole inquiry into those higher relations of parts to the archetype which Sir

text: Richard Owen

text: (1804–1892) called "general homologies."

text: The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed external armor that protected them from predators. The first fish with jaws appeared in the Silurian period, after which many (such as sharks) became formidable marine predators rather than just the prey of arthropods.

text: The earliest organisms that can be classified as fish were soft-bodied

text: chordate

text: s that first appeared during the

text: Cambrian

text: period. Although they lacked a

text: true spine

text: , they possessed

text: notochord

text: s which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the

text: Paleozoic

text: era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed

text: external armor

text: that protected them from predators. The first fish with

text: jaw

text: s appeared in the

text: Silurian

text: period, after which many (such as

text: shark

text: s) became formidable marine predators rather than just the prey of

text: arthropod

text: s.

text: The term coccyx is derived from the ancient Greek word κόκκυξ kokkyx "cuckoo"; the latter is attested in the writings of the Greek physician Herophilus to denote the end of the vertebral column. This Greek name for the cuckoo was applied as the last three or four bones of the coccyx resemble the beak of this bird, when viewed from the side.

text: The term coccyx is derived from the

text: ancient Greek

text: word κόκκυξ kokkyx "cuckoo"; the latter is attested in the writings of the Greek

text: physician

text: Herophilus

text: to denote the end of the vertebral column. This Greek name for the

text: cuckoo

text: was applied as the last three or four bones of the coccyx resemble the beak of this bird, when viewed from the side.

text: Some protists reproduce sexually using gametes, while others reproduce asexually by binary fission.

text: Some protists reproduce

text: sexually

text: using

text: gametes

text: , while others reproduce

text: asexually

text: by

text: binary fission

text: Cartilage erosion may progress to the point that the bone underneath will become exposed. With the cartilage no longer present to protect it, the navicular bursa and DDF tendon may become damaged by the constant rubbing against the navicular bone. Navicular bursitis (inflammation of the navicular bursa) may occur, even if cartilage damage is not severe. This is probably due to the friction between the navicular bone and the DDF tendon from compression.

text: Nuclear scintigraphy, or the "bone scan," involves injecting a radioactive substance, often technetium-99, into the horse and then measuring uptake, which is strongest in the areas of rapid bone remodeling. The bone scan is often useful for lameness that can’t be easily localized to one area, that affects multiple limbs, or lameness that is thought to originate in areas not easily imaged by other means, such as the vertebral column. Although it provides localization for lameness, it does not give a definitive diagnosis. The availability of this modality is more limited relative to radiographs and ultrasound, and usually requires referral to a secondary care facility. Additionally, the horse must stay for a short period of time until it is no longer radioactive.  It is relatively non-invasive, requiring an initial injection of the radioisotope, and sedation throughout the procedure.

text: Nuclear scintigraphy, or the "bone scan," involves injecting a radioactive substance, often

text: , into the horse and then measuring uptake, which is strongest in the areas of rapid bone remodeling. The bone scan is often useful for lameness that can’t be easily localized to one area, that affects multiple limbs, or lameness that is thought to originate in areas not easily imaged by other means, such as the vertebral column. Although it provides localization for lameness, it does not give a definitive diagnosis. The availability of this modality is more limited relative to radiographs and ultrasound, and usually requires referral to a secondary care facility. Additionally, the horse must stay for a short period of time until it is no longer radioactive.  It is relatively non-invasive, requiring an initial injection of the radioisotope, and sedation throughout the procedure.

text: The known non-arboviruses of the flavivirus family reproduce in either arthropods or vertebrates, but not both, with one odd member of the genus affecting a nematode.

text: The known non-arboviruses of the flavivirus family reproduce in either arthropods or vertebrates, but not both, with one odd member of the genus affecting a

text: nematode

text: Most fish are completely cold-blooded. Some, such as tuna and lamnid sharks (particularly the salmon shark), have evolved regional endothermy, in which parts of the body core are kept at a warmer temperature. These fish have retia arranged to warm muscles used for propulsion, and some visceral organs, while other organs, such as the heart, remain cooler. Only L. guttatus is known to have retia within its gill arches (which are also insulated by fat), an arrangement that warms the entire body core including the heart.

text: Most fish are completely

text: cold-blooded

text: . Some, such as tuna and lamnid sharks (particularly the

text: salmon shark

text: ), have evolved regional endothermy, in which parts of the body core are kept at a warmer temperature. These fish have retia arranged to warm muscles used for propulsion, and some visceral organs, while other organs, such as the heart, remain cooler. Only L. guttatus is known to have retia within its

text: gill arch

text: es (which are also insulated by fat), an arrangement that warms the entire body core including the heart.

text: Patients with an advanced case may present some or none of the symptoms associated with general cases of vertebral osteomyelitis. When the osteomyelitis is isolated in the back, as it is in vertebral osteomyelitis, the patient will report muscle spasms coming from the back, but may not report experiencing any fevers. Symptomatic signs vary in each patient and depend on the severity of the case. Neurologic deficiency characterizes advanced, threatening cases of the disease. On average, 40% of patients with an advanced case of vertebral osteomyelitis experience some type of neurological deficiency; this is a sign that the infection has been progressing for some time. In advanced cases, the untreated infection will attack the nervous system through the spinal cord which runs parallel to the vertebral column, placing the patient at risk for paralysis of the extremities. Additionally, loss of the ability to move is a trademark symptom of neurologic problems in advanced cases of vertebral osteomyelitis. Any further signs of neurological deficit signal an advanced case of vertebral osteomyelitis that requires immediate intervention to prevent further threat to the spinal cord.

text: Patients with an advanced case may present some or none of the symptoms associated with general cases of vertebral osteomyelitis. When the osteomyelitis is isolated in the back, as it is in vertebral osteomyelitis, the patient will report muscle spasms coming from the back, but may not report experiencing any fevers. Symptomatic signs vary in each patient and depend on the severity of the case. Neurologic deficiency characterizes advanced, threatening cases of the disease. On average, 40% of patients with an advanced case of vertebral osteomyelitis experience some type of neurological deficiency; this is a sign that the infection has been progressing for some time. In advanced cases, the untreated infection will attack the nervous system through the spinal cord which runs parallel to the vertebral column, placing the patient at risk for paralysis of the extremities. Additionally, loss of the ability to move is a trademark symptom of neurologic problems in advanced cases of vertebral osteomyelitis. Any further signs of

entity_name: Functional neurological symptom disorder

text: neurological deficit

text: signal an advanced case of vertebral osteomyelitis that requires immediate intervention to prevent further threat to the spinal cord.

text: Polychaetes can reproduce asexually, by dividing into two or more pieces or by budding off a new individual while the parent remains a complete organism. Some oligochaetes, such as Aulophorus furcatus, seem to reproduce entirely asexually, while others reproduce asexually in summer and sexually in autumn. Asexual reproduction in oligochaetes is always by dividing into two or more pieces, rather than by budding. However, leeches have never been seen reproducing asexually.

text: Polychaete

text: s can reproduce asexually, by dividing into two or more pieces or by

text: budding

text: off a new individual while the parent remains a complete organism. Some

text: oligochaete

text: s, such as

text: Aulophorus

text: furcatus, seem to reproduce entirely asexually, while others reproduce asexually in summer and sexually in autumn. Asexual reproduction in oligochaetes is always by dividing into two or more pieces, rather than by budding. However,

text: leech

text: es have never been seen reproducing asexually.

text: Surrounding structures such as the notochord, neural tube, epidermis and lateral plate mesoderm send signals for somite differentiation Notochord protein accumulates in presomitic mesoderm destined to form the next somite and then decreases as that somite is established. The notochord and the neural tube activate the protein SHH  which helps the somite to form its sclerotome. The cells of the sclerotome express the protein PAX1 that induces the cartilage and bone formation. The neural tube activates the protein WNT1 that expresses PAX 2 so the somite creates the myotome and dermatome. Finally, the neural tube also secretes neurotrophin 3 (NT-3), so that the somite creates the dermis. Boundaries for each somite are regulated by retinoic acid (RA) and a combination of FGF8 and WNT3a. So the retinoic acid is an endogenous signal that maintains the bilateral synchrony of mesoderm segmentation and controls bilateral symmetry in vertebrates. The bilaterally symmetric body plan of vertebrate embryos is obvious in somites and their derivates such as the vertebral column. Therefore, asymmetric somite formation correlates with a left-right desynchronization of the segmentation oscillations.

text: There are six somatostatin genes that have been discovered in vertebrates. The current proposed history as to how these six genes arose is based on the three whole-genome duplication events that took place in vertebrate evolution along with local duplications in teleost fish. An ancestral somatostatin gene was duplicated during the first whole-genome duplication event (1R) to create SS1 and SS2. These two genes were duplicated during the second whole-genome duplication event (2R) to create four new somatostatin genes: SS1, SS2, SS3, and one gene that was lost during the evolution of vertebrates. Tetrapods retained SS1 (also known as SS-14 and SS-28) and SS2 (also known as cortistatin) after the split in the sarcopterygii and actinopterygii lineage split. In teleost fish, SS1, SS2, and SS3 were duplicated during the third whole-genome duplication event (3R) to create SS1, SS2, SS4, SS5, and two genes that were lost during the evolution of teleost fish. SS1 and SS2 went through local duplications to give rise to SS6 and SS3.

text: There are six somatostatin genes that have been discovered in

text: vertebrates

text: . The current proposed history as to how these six genes arose is based on the three whole-genome duplication events that took place in vertebrate evolution along with local duplications in

text: teleost

text: fish. An ancestral somatostatin gene was duplicated during the first

text: whole-genome duplication event

text: (1R) to create SS1 and SS2. These two genes were duplicated during the second whole-genome duplication event (2R) to create four new somatostatin genes: SS1, SS2, SS3, and one gene that was lost during the evolution of vertebrates.

text: Tetrapods

text: retained SS1 (also known as SS-14 and SS-28) and SS2 (also known as

text: cortistatin

text: ) after the split in the

text: sarcopterygii

text: and

text: actinopterygii

text: lineage split. In

text: teleost

text: fish, SS1, SS2, and SS3 were duplicated during the third whole-genome duplication event (3R) to create SS1, SS2, SS4, SS5, and two genes that were lost during the evolution of teleost fish. SS1 and SS2 went through local duplications to give rise to SS6 and SS3.

text: Lampreys have vertebral arches, but nothing resembling the vertebral bodies found in all higher vertebrates. Even the arches are discontinuous, consisting of separate pieces of arch-shaped cartilage around the spinal cord in most parts of the body, changing to long strips of cartilage above and below in the tail region. Hagfishes lack a true vertebral column, and are therefore not properly considered vertebrates, but a few tiny neural arches are present in the tail.

text: Lamprey

text: higher vertebrates

text: Hagfish

text: es lack a true vertebral column, and are therefore not properly considered vertebrates, but a few tiny neural arches are present in the tail.

text: Invertebrates are grouped into different phyla. Informally phyla can be thought of as a way of grouping organisms according to their body plan. A body plan refers to a blueprint which describes the shape or morphology of an organism,  such as its symmetry, segmentation and the disposition of its appendages. The idea of body plans originated with vertebrates, which were grouped into one phylum. But the vertebrate body plan is only one of many, and invertebrates consist of many phyla or body plans. The history of the discovery of body plans can be seen as a movement from a worldview centred on vertebrates, to seeing the vertebrates as one body plan among many. Among the pioneering zoologists, Linnaeus identified two body plans outside the vertebrates; Cuvier identified three; and Haeckel had four, as well as the Protista with eight more, for a total of twelve. For comparison, the number of phyla recognised by modern zoologists has risen to 35.

text: Invertebrates are grouped into different

text: phyla

text: . Informally phyla can be thought of as a way of grouping organisms according to their

text: body plan

text: . A body plan refers to a blueprint which describes the shape or

text: morphology

text: of an organism,  such as its

text: symmetry

text: segmentation

text: and the disposition of its

text: appendage

text: s. The idea of body plans originated with

text: vertebrate

text: s, which were grouped into one phylum. But the vertebrate body plan is only one of many, and invertebrates consist of many phyla or body plans. The history of the discovery of body plans can be seen as a movement from a worldview centred on vertebrates, to seeing the vertebrates as one body plan among many. Among the pioneering

text: zoologist

text: s, Linnaeus identified two body plans outside the vertebrates; Cuvier identified three; and Haeckel had four, as well as the Protista with eight more, for a total of twelve. For comparison, the number of phyla recognised by modern zoologists has

text: risen to 35

text: Parallel to the evolution of the cochlea, prestins show an increased rate of evolution in therian mammals. Prestins are located in the outer hair cells of mammalian cochlea and are considered motor proteins. They are found in the hair cells of all vertebrates, including fish, but are thought to have initially been membrane transporter molecules. A high concentration of prestins are found only in the lateral membranes of therian outer hair cells (there is uncertainty with regard to concentrations in monotremes). This high concentration is not found in inner hair cells, and is also lacking in all hair cell types of non-mammals.  Prestin also has a role in motility, which evolved a greater importance in the motor function in land vertebrates, but this developed vastly differently in different lineages. In certain birds and mammals, prestins function as both transporters and motors, but the strongest evolution to robust motor dynamics only evolved in therian mammals. It is hypothesized that this motor system is significant to the therian cochlea at high frequencies because of the distinctive cellular and bony composition of the organ of Corti that allows the prestins to intensify movements of the whole structure.Modern ultra-sound echolocating species such as bats and toothed whales show highly evolved prestins, and these prestins show identical sequence alterations over time. Unusually, the sequences thus apparently evolved independent from each other during different time periods. Furthermore, the evolution of neurotransmitter receptor systems (acetylcholine) that regulate the motor feedback of the outer hair cells coincides with prestin evolution in therians. This suggests that there was a parallel evolution of a control system and a motor system in the inner ear of therian mammals.

text: Parallel to the evolution of the cochlea,

text: prestins

text: Stanley Olsen was a member of the Society of Vertebrate Paleontology, the Society for American Archaeology, the Society of the Sigma Xi, the Society of Mammalogists, and the American Society of Systematic Zoologists.  He was a Fellow of both the Explorers Club and the Company of Military Historians.  He served as the 26th President of the Society of Vertebrate Paleontology in 1965-1966 and was elected an Honorary Member in 1996 (the 50th anniversary of his joining the Society) in recognition of Olsen’s distinguished contributions to the discipline of vertebrate paleontology.

text: Stanley Olsen was a member of the

text: Society of Vertebrate Paleontology

text: , the

text: Society for American Archaeology

text: , the Society of the

text: Sigma Xi

text: , the Society of Mammalogists, and the American Society of Systematic Zoologists.  He was a Fellow of both the

text: Explorers Club

text: and the

text: Company of Military Historians

text: .  He served as the 26th President of the

text: Society of Vertebrate Paleontology

text: in 1965-1966 and was elected an Honorary Member in 1996 (the 50th anniversary of his joining the Society) in recognition of Olsen’s distinguished contributions to the discipline of vertebrate paleontology.

text: It can usually be corrected with augmentation rhinoplasty by filling the dorsum of nose with cartilage, bone or synthetic implant. If the depression is only cartilaginous, cartilage is taken from the nasal septum or auricle and laid in single or multiple layers. If deformity involves both cartilage and bone, cancellous bone from iliac crest is the best replacement. Autografts are preferred over allografts. Saddle deformity can also be corrected by synthetic implants of teflon or silicon, but they are likely to be extruded.

text: It can usually be corrected with augmentation

text: rhinoplasty

text: by filling the dorsum of nose with cartilage, bone or synthetic implant. If the depression is only cartilaginous, cartilage is taken from the nasal septum or auricle and laid in single or multiple layers. If deformity involves both cartilage and bone, cancellous bone from

text: iliac crest

text: is the best replacement.

text: Autograft

text: s are preferred over

text: allograft

text: s. Saddle deformity can also be corrected by synthetic implants of

text: teflon

text: or silicon, but they are likely to be extruded.

text: Orange spotted filefish absorb and use chemicals in the Acropora coral they eat to take on its smell, which cloaks them from natural predators like cod. In addition to this trait, not observed among other vertebrates, they also use visual camouflage.

text: Orange spotted filefish absorb and use chemicals in the

text: Acropora

text: coral they eat to take on its smell, which cloaks them from natural predators like

text: cod

text: . In addition to this trait, not observed among other

text: vertebrate

text: s, they also use visual

text: camouflage

text: A number of interesting experimental results have been obtained by studying MED12 mutations in the zebrafish, an animal model representing vertebrates.  In zebrafish, a mutation in MED12 was found to be responsible for the mutant motionless (mot).  Zebrafish with the mot mutation have neuronal and cardiovascular defects, although not all types of neurons are affected. Introduction of human MED12 mRNA into the zebrafish restores normal development.  MED12 is also a critical coactivator for the gene SOX9, which is involved in the developmental regulation of neurons, cartilage and bone. In the zebrafish, MED12 defects cause maldevelopment of vertebrate embryonic structures such as the neural crest, which would alter function of the autonomic and peripheral nervous systems; and they also cause malformations of cell types serving as precursors to cartilage and bone, such as osteocytes.  Some features found in LFS, like agenesis of the corpus callosum and cartilage-related craniofacial anomalies, are similar to defects found in zebrafish with MED12 and associated mutations.

text: A number of interesting experimental results have been obtained by studying MED12 mutations in the

text: zebrafish

text: , an

text: animal model

text: representing

text: vertebrate

text: s.  In zebrafish, a mutation in MED12 was found to be responsible for the mutant motionless (mot).  Zebrafish with the mot mutation have neuronal and cardiovascular defects, although not all types of neurons are affected. Introduction of human MED12 mRNA into the zebrafish restores normal development.  MED12 is also a critical

text: coactivator

text: for the gene

text: , which is involved in the developmental regulation of neurons,

text: cartilage

text: and

text: bone

text: . In the zebrafish, MED12 defects cause maldevelopment of vertebrate embryonic structures such as the

text: neural crest

text: , which would alter function of the

text: autonomic

text: and

text: peripheral nervous system

text: s; and they also cause malformations of

text: cell type

text: s serving as precursors to

text: cartilage

text: and

text: bone

text: , such as

text: osteocyte

text: s.  Some features found in LFS, like agenesis of the corpus callosum and cartilage-related craniofacial anomalies, are similar to defects found in zebrafish with MED12 and associated mutations.

text: The Fauna of Saskatchewan include several diverse land and aquatic animal species. From the multiplicity of invertebrates and vertebrates, two have been chosen as symbols of Saskatchewan. Cenozoic vertebrate fossils reveal the geological evolution of the interior plains and its prehistoric biogeography. Today, Saskatchewan's ecosystems range from the sub-arctic tundra of the Canadian Shield in north Saskatchewan to aspen parkland, the Mid-Continental Canadian forests in the centre of the province and grassland prairie. Fauna inhabit areas unique to their own specific and varied breeding, foraging and nesting requirements. With a large land and water area, and small population density, the ecoregions of Saskatchewan provide important habitat for many animals, both endangered and not. Naturalists observing wildlife have enumerated shrinking and growing wildlife populations. They advocate programs and methods to preserve or re-introduce endangered species and identify programs of control for outbreaks of wildlife populations. A broad diversity of wildlife habitats are preserved as parks and reserves protecting the feeding and breeding grounds of protected and indigenous fauna of Saskatchewan.

text: The

text: Fauna

text: of

text: Saskatchewan

text: include several diverse land and aquatic

text: animal

text: species

text: . From the multiplicity of

text: invertebrate

text: s and

text: vertebrate

text: s, two have been chosen as

text: symbols of Saskatchewan

text: Cenozoic

text: vertebrate

text: fossil

text: s reveal the

text: geological evolution

text: of the

text: interior plains

text: and its prehistoric biogeography. Today, Saskatchewan's ecosystems range from the

text: sub-arctic

text: tundra

text: of the

text: Canadian Shield

text: in north Saskatchewan to

text: aspen parkland

text: , the

text: Mid-Continental Canadian forests

text: in the centre of the province and grassland

text: prairie

text: . Fauna inhabit areas unique to their own specific and varied breeding, foraging and nesting requirements. With a large land and water area, and small population density, the

text: ecoregions of Saskatchewan

text: provide important habitat for many animals, both endangered and not. Naturalists observing wildlife have enumerated shrinking and growing wildlife populations. They advocate programs and methods to preserve or re-introduce

text: endangered species

text: and identify programs of control for outbreaks of wildlife populations. A broad diversity of wildlife habitats are preserved as parks and reserves protecting the feeding and breeding grounds of protected and indigenous fauna of Saskatchewan.

text: Studies conducted in the North Cascades National Park Service Complex examined impacts on larval stage long-toed salamanders through snorkel observations. The long-toed salamander is considered the top vertebrate predator in high-elevation fishless lakes, but the presence of fish species often equates to lower densities of larvae.  While fish impact is a notable factor, fish predation is more commonly linked to changes in salamander behavior, particularly nocturnal tendencies. As lakes decrease in elevation and Scientists have examined additional abiotic and biotic factors that lead to declines of salamanders in lake ecosystems. Elevation, water temperature, lake area and depth, as well as availability of suitable food resources, are all factors that interact with fish introductions to influence impacts. Amphibian declines have become a worldwide issue that is most commonly attributed to chemical pollution, acid rain, ozone depletion, habitat destruction, as well as introductions of exotic species Recent studies have shown correlations of decline among amphibians to a chytrid fungus, which causes chytridiomycosis. The pathogen is one of many emerging infectious diseases that largely threaten amphibian populations, especially salamanders. Primarily spread through the import/export of live animals the threat lies when infected animals escape or are released into the wild.

text: Studies conducted in the

text: North Cascades National Park Service Complex

text: examined impacts on larval stage long-toed salamanders through snorkel observations. The

text: long-toed salamander

text: is considered the top vertebrate predator in high-elevation fishless lakes, but the presence of fish species often equates to lower densities of larvae.  While fish impact is a notable factor, fish predation is more commonly linked to changes in salamander behavior, particularly nocturnal tendencies. As lakes decrease in elevation and Scientists have examined additional abiotic and biotic factors that lead to declines of salamanders in lake ecosystems. Elevation, water temperature, lake area and depth, as well as availability of suitable food resources, are all factors that interact with fish introductions to influence impacts. Amphibian declines have become a worldwide issue that is most commonly attributed to chemical pollution, acid rain, ozone depletion, habitat destruction, as well as introductions of exotic species Recent studies have shown correlations of decline among amphibians to a chytrid fungus, which causes

text: chytridiomycosis

text: . The pathogen is one of many emerging infectious diseases that largely threaten amphibian populations, especially salamanders. Primarily spread through the import/export of live animals the threat lies when infected animals escape or are released into the wild.

text: The predominant population affected by the snake's introduction was that of native bird species such as the Mariana fruit dove, the Guam flycatcher, the rufous fantail and the Micronesian myzomela. The introduction of the brown tree snake into Guam has resulted in extinction of twelve native bird species in total. The Guam National Wildlife Refuge is attempting to prevent the extinction of additional bird species endangered by the snake. Other species significantly affected by the invasion of these snakes were small lizards and small mammals.  Research has indicated a direct correlation of the spread of these snakes across the island to the decrease in the populations of these native species. Furthermore, the introduction of the brown tree snake has had an indirect, negative impact on vegetative diversity as its intense predatory nature has decreased populations of vital pollinators including native birds and fruit bats. Data collected from nearby islands lacking brown tree snake populations depict a significant difference in vegetative species richness, that is, islands close to and similar to Guam in which the brown tree snake has not been introduced have greater vegetative species diversity. Overall, the vertebrate fauna and native flora of Guam have suffered tremendously because of the introduction of the brown tree snake.

text: The predominant population affected by the snake's introduction was that of native bird species such as the

text: Mariana fruit dove

text: , the

text: Guam flycatcher

text: , the

text: rufous fantail

text: and the

text: Micronesian myzomela

text: . The introduction of the brown tree snake into Guam has resulted in

text: extinction

text: of twelve native bird species in total. The

text: Guam National Wildlife Refuge

text: is attempting to prevent the extinction of additional bird species endangered by the snake. Other species significantly affected by the invasion of these snakes were small lizards and small mammals.  Research has indicated a direct correlation of the spread of these snakes across the island to the decrease in the populations of these native species. Furthermore, the introduction of the brown tree snake has had an indirect, negative impact on vegetative diversity as its intense predatory nature has decreased populations of vital

text: pollinators

text: including native birds and

text: fruit bats

text: . Data collected from nearby islands lacking brown tree snake populations depict a significant difference in vegetative

text: species richness

text: , that is, islands close to and similar to Guam in which the brown tree snake has not been introduced have greater vegetative

text: species diversity

text: . Overall, the vertebrate

text: fauna

text: and native

text: flora

text: of Guam have suffered tremendously because of the introduction of the brown tree snake.

text: Through his textbook Vertebrate Paleontology Romer laid the foundation for the traditional classification of vertebrates. He drew together the (then) widely scattered taxonomy of the different vertebrate groups and combined them in a simplified scheme, emphasizing orderliness and overview. Based on his research of early amphibians, he reorganised the labyrinthodontians.  Romer's classification was followed by many subsequent authors, notably Robert L. Carroll, and is still in use.

text: Through his textbook

text: Vertebrate Paleontology

text: Romer laid the foundation for the traditional classification of vertebrates. He drew together the (then) widely scattered taxonomy of the different vertebrate groups and combined them in a simplified scheme, emphasizing orderliness and overview. Based on his research of early amphibians, he reorganised the

text: labyrinthodontia

text: ns.

text: Romer's classification

text: was followed by many subsequent authors, notably

text: Robert L. Carroll

text: , and is still in use.

text: Like all species in this genus it has both vertebrate and insect hosts. The vertebrate host are birds.

text: Like all species in this genus it has both

text: vertebrate

text: and

text: insect

text: hosts. The vertebrate host are

text: bird

text: s.

text: Like all Plasmodium species P. carmelinoi has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. carmelinoi has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: Cephalopods, as active marine predators, possess sensory organs specialized for use in aquatic conditions.  They have a camera-type eye which consists of an iris, a circular lens, vitreous cavity (eye gel), pigment cells, and photoreceptor cells that translate light from the light-sensitive retina into nerve signals which travel along the optic nerve to the brain. For the past 140 years, the camera-type cephalopod eye has been compared with the vertebrate eye as an example of convergent evolution, where both types of organisms have independently evolved the camera-eye trait and both share similar functionality. Contention exists on whether this is truly convergent evolution or parallel evolution. Unlike the vertebrate camera eye, the cephalopods' form as invaginations of the body surface (rather than outgrowths of the brain), and consequently they lack a cornea.  Unlike the vertebrate eye, a cephalopod eye is focused through movement, much like the lens of a camera or telescope, rather than changing shape as the lens in the human eye does. The eye is approximately spherical, as is the lens, which is fully internal.

text: Cephalopods

text: , as active marine predators, possess sensory organs specialized for use in aquatic conditions.  They have a

text: camera-type eye

text: which consists of an iris, a circular lens, vitreous cavity (eye gel), pigment cells, and photoreceptor cells that translate light from the light-sensitive

text: retina

text: into nerve signals which travel along the optic nerve to the brain. For the past 140 years, the camera-type cephalopod eye has been compared with the vertebrate eye as an example of

text: convergent evolution

text: , where both types of organisms have independently evolved the camera-eye trait and both share similar functionality. Contention exists on whether this is truly convergent evolution or

text: parallel evolution

text: . Unlike the

text: vertebrate

text: camera eye, the cephalopods' form as

text: invagination

text: s of the body surface (rather than outgrowths of the brain), and consequently they lack a

text: cornea

text: .  Unlike the vertebrate eye, a cephalopod eye is focused through movement, much like the lens of a camera or telescope, rather than changing shape as the lens in the human eye does. The

text: eye

text: is approximately spherical, as is the

text: lens

text: , which is fully internal.

text: Taxonomists place lampreys and hagfish in the subphylum Vertebrata of the phylum Chordata, which also includes the invertebrate subphyla Tunicata (sea-squirts) and the fish-like Cephalochordata (lancelets or Amphioxus). Recent molecular and morphological phylogenetic studies place lampreys and hagfish in the superclass Agnatha or Agnathostomata (both meaning without jaws). The other vertebrate superclass is Gnathostomata (jawed mouths) and includes the classes Chondrichthyes (sharks), Osteichthyes (bony fishes), Amphibia, Reptilia, Aves, and Mammalia.

text: Taxonomists place lampreys and hagfish in the subphylum

text: Vertebrata

text: of the

text: phylum

text: Chordata

text: , which also includes the invertebrate subphyla

text: Tunicata

text: (sea-squirts) and the fish-like

text: Cephalochordata

text: lancelet

text: s or Amphioxus). Recent molecular and morphological phylogenetic studies place lampreys and hagfish in the superclass

text: Agnatha

text: or

text: Agnathostomata

text: (both meaning without jaws). The other vertebrate superclass is

text: Gnathostomata

text: (jawed mouths) and includes the classes

text: Chondrichthyes

text: (sharks),

text: Osteichthyes

text: (bony fishes),

text: Amphibia

text: Reptilia

text: Aves

text: , and

text: Mammalia

text: Triumph of the Vertebrates is a 2013 British documentary film by David Attenborough. It is about the evolution of vertebrates. The first part is From the Seas to the Skies, while the second part is Dawn of the Mammals.

text: Triumph of the Vertebrates is a 2013 British

text: documentary film

text: by

text: David Attenborough

text: . It is about the

text: evolution

text: of

text: vertebrates

text: . The first part is From the Seas to the Skies, while the second part is Dawn of the Mammals.

text: In prehistoric Oklahoma, Astrodon lived alongside other dinosaurs, such as the sauropod Sauroposeidon proteles, the dromaeosaurid Deinonychus and the carnosaur Acrocanthosaurus atokensis. The most common dinosaur in the paleoenvironment preserved in the Antlers Formation is the ornithopod Tenontosaurus. Other vertebrates present at the time of Astrodon included the amphibian Albanerpeton arthridion, the reptiles Atokasaurus metarsiodon and Ptilotodon wilsoni, the crurotarsan reptile Bernissartia, the cartilaginous fish Hybodus buderi and Lissodus anitae, the ray-finned fish Gyronchus dumblei, the crocodilian Goniopholis, and the turtles Glyptops and Naomichelys. Possible indeterminate bird remains are also known from this formation. The fossil evidence suggests that the gar Lepisosteus was the most common vertebrate in this region. The early mammals known from this region include Atokatherium boreni and Paracimexomys crossi.

text: In prehistoric Oklahoma, Astrodon lived alongside other dinosaurs, such as the

text: sauropod

text: Sauroposeidon

text: proteles, the

text: dromaeosaurid

text: Deinonychus

text: and the

text: carnosaur

text: Acrocanthosaurus

text: atokensis. The most common dinosaur in the paleoenvironment preserved in the Antlers Formation is the

text: ornithopod

text: Tenontosaurus

text: . Other vertebrates present at the time of Astrodon included the

text: amphibian

text: Albanerpeton

text: arthridion, the reptiles Atokasaurus metarsiodon and Ptilotodon wilsoni, the

text: crurotarsan

text: reptile

text: Bernissartia

text: , the

text: cartilaginous

text: fish

text: Hybodus

text: buderi and

text: Lissodus

text: anitae, the

text: ray-finned

text: fish

text: Gyronchus

text: dumblei, the crocodilian

text: Goniopholis

text: , and the turtles

text: Glyptops

text: and Naomichelys. Possible indeterminate bird remains are also known from this formation. The fossil evidence suggests that the

text: gar

text: Lepisosteus

text: was the most common vertebrate in this region. The early mammals known from this region include Atokatherium boreni and

text: Paracimexomys

text: crossi.

text: Other features that may form part of the syndrome include precocious costal calcification, small iliac bones, short femoral necks, coxa vara, short halluces and fused vertebral bodies.

text: Other features that may form part of the syndrome include precocious costal calcification, small

text: iliac bone

text: s, short femoral necks, coxa vara, short

text: halluce

text: s and fused vertebral bodies.

text: The first ancestors of fish, or animals that were probably closely related to fish, were Pikaia, Haikouichthys and Myllokunmingia. These three genera all appeared around 530 Ma. Pikaia had a primitive notochord, a structure that could have developed into a vertebral column later. Unlike the other fauna that dominated the Cambrian, these groups had the basic vertebrate body plan: a notochord, rudimentary vertebrae, and a well-defined head and tail. All of these early vertebrates lacked jaws in the common sense and relied on filter feeding close to the seabed.

text: The first ancestors of fish, or animals that were probably closely related to fish, were

text: Pikaia

text: Haikouichthys

text: and

text: Myllokunmingia

text: . These three

text: genera

text: all appeared around 530

text: Ma

text: . Pikaia had a primitive

text: notochord

text: , a structure that could have developed into a

text: vertebral column

text: later. Unlike the other fauna that dominated the Cambrian, these groups had the basic vertebrate

text: body plan

text: : a

text: notochord

text: , rudimentary vertebrae, and a well-defined head and tail. All of these early vertebrates lacked

text: jaw

text: s in the common sense and relied on filter feeding close to the seabed.

text: The Journal of Vertebrate Paleontology (JVP) was founded in 1980 at the University of Oklahoma by Dr. Jiri Zidek.  It is a scientific journal that publishes original contributions on all aspects of the vertebrate paleontology, including vertebrate origins, evolution, functional morphology, taxonomy, biostratigraphy, paleoecology, paleobiogeography, and paleoanthropology.

text: The Journal of Vertebrate Paleontology (JVP) was founded in 1980 at the

text: University of Oklahoma

text: by Dr.

text: Jiri Zidek

text: .  It is a

text: scientific journal

text: that publishes original contributions on all aspects of the

text: vertebrate paleontology

text: , including

text: vertebrate origins

text: evolution

text: functional morphology

text: taxonomy

text: biostratigraphy

text: paleoecology

text: paleobiogeography

text: , and

text: paleoanthropology

text: Like all Plasmodium species P. lagopi has both vertebrate and insect hosts. The vertebrate hosts for this parasite are birds.

text: Like all Plasmodium species P. lagopi has both

text: vertebrate

text: and

text: insect

text: bird

text: s.

text: His research includes many aspects of lipid digestion and absorption, bile acid evolution, pathobiology, and pathochemistry, bile secretion, cholelithiasis, biliary physiology and pharmacology, and the diagnosis and treatment of various digestive and hepatobiliary diseases. Together with his longtime collaborator, Lee Hagey, he has written a comprehensive history of bile acid research. Making the most of his proximity to the San Diego Zoo, his publications have help define the wide bile acid diversity found in different vertebrates.

text: His research includes many aspects of

text: lipid

text: digestion

text: and absorption,

text: bile acid

text: evolution, pathobiology, and pathochemistry,

text: bile

text: secretion,

text: cholelithiasis

text: , biliary physiology and pharmacology, and the diagnosis and treatment of various digestive and hepatobiliary diseases. Together with his longtime collaborator, Lee Hagey, he has written a comprehensive history of bile acid research. Making the most of his proximity to the

text: San Diego Zoo

text: , his publications have help define the wide bile acid diversity found in different vertebrates.

text: Mammals are unique in having evolved a three-ossicle middle-ear independently of the various single-ossicle middle ears of other land vertebrates, all during the Triassic period of geological history. Functionally, the mammalian middle ear is very similar to the single-ossicle ear of non-mammals, except that it responds to sounds of higher frequency, because these are better taken up by the inner ear (which also responds to higher frequencies than those of non-mammals). The malleus, or "hammer", evolved from the articular bone of the lower jaw, and the incus, or "anvil", from the quadrate. In other vertebrates, these bones form the primary jaw joint, but the expansion of the dentary bone in mammals led to the evolution of an entirely new jaw joint, freeing up the old joint to become part of the ear. For a period of time, both jaw joints existed together, one medially and one laterally. The evolutionary process leading to a three-ossicle middle ear was thus an "accidental" byproduct of the simultaneous evolution of the new, secondary  jaw joint. In many mammals, the middle ear also becomes protected within a cavity, the auditory bulla, not found in other vertebrates. A bulla evolved late in time and independently numerous times in different mammalian clades, and it can be surrounded by membranes, cartilage or bone. The bulla in humans is part of the temporal bone.

text: Mammals are unique in having evolved a three-ossicle middle-ear independently of the various single-ossicle middle ears of other land vertebrates, all during the Triassic period of geological history. Functionally, the mammalian middle ear is very similar to the single-ossicle ear of non-mammals, except that it responds to sounds of higher frequency, because these are better taken up by the inner ear (which also responds to higher frequencies than those of non-mammals). The malleus, or "hammer", evolved from the

text: articular

text: bone of the lower jaw, and the incus, or "anvil", from the quadrate. In other vertebrates, these bones form the primary jaw joint, but the expansion of the

text: dentary

text: bone in mammals led to the evolution of an entirely new jaw joint, freeing up the old joint to become part of the ear. For a period of time, both jaw joints existed together, one medially and one laterally. The evolutionary process leading to a three-ossicle middle ear was thus an "accidental" byproduct of the simultaneous evolution of the new, secondary  jaw joint. In many mammals, the middle ear also becomes protected within a cavity, the

text: auditory bulla

text: , not found in other vertebrates. A bulla evolved late in time and independently numerous times in different mammalian clades, and it can be surrounded by membranes, cartilage or bone. The bulla in humans is part of the

text: temporal bone

text: All vertebrate brains share a common underlying form, which appears most clearly during early stages of embryonic development. In its earliest form, the brain appears as three swellings at the front end of the neural tube; these swellings eventually become the forebrain, midbrain, and hindbrain (the prosencephalon, mesencephalon, and rhombencephalon, respectively). At the earliest stages of brain development, the three areas are roughly equal in size. In many classes of vertebrates, such as fish and amphibians, the three parts remain similar in size in the adult, but in mammals the forebrain becomes much larger than the other parts, and the midbrain becomes very small.

text: All vertebrate brains share a common underlying form, which appears most clearly during early stages of embryonic development. In its earliest form, the brain appears as three swellings at the front end of the

text: neural tube

text: ; these swellings eventually become the forebrain, midbrain, and hindbrain (the

text: prosencephalon

text: mesencephalon

text: , and

text: rhombencephalon

text: , respectively). At the earliest stages of brain development, the three areas are roughly equal in size. In many classes of vertebrates, such as fish and amphibians, the three parts remain similar in size in the adult, but in mammals the forebrain becomes much larger than the other parts, and the midbrain becomes very small.

text: One of the best-known examples of convergent evolution is the camera eye of cephalopods (such as squid and octopus), vertebrates (including mammals) and cnidaria (such as jellyfish).  Their last common ancestor had at most a simple photoreceptive spot, but a range of processes led to the progressive refinement of camera eyes — with one sharp difference: the cephalopod eye is "wired" in the opposite direction, with blood and nerve vessels entering from the back of the retina, rather than the front as in vertebrates. This means that cephalopods do not have a blind spot.

text: One of the best-known examples of convergent evolution is the camera eye of

text: cephalopods

text: (such as squid and octopus),

text: vertebrate

text: s (including mammals) and

text: cnidaria

text: (such as jellyfish).  Their last common ancestor had at most a simple photoreceptive spot, but a range of processes led to the

text: progressive refinement of camera eyes

text: — with one sharp difference: the cephalopod eye is "wired" in the opposite direction, with blood and nerve vessels entering from the back of the retina, rather than the front as in vertebrates. This means that cephalopods do not have a blind spot.

text: Theorists believe that creating a concept includes learning the distinct features and characteristics that are present in all examples of a concept. A good way to know if something is part of a concept is to identify the defining features of the concept and see if the object or event in question shares those defining features. For example, an animal must eat food, a plant must grow, and a vertebrate must have a spine. So, every example of an animal must have the defining feature or eating food, every plant must grow, and every vertebrate must have a spine to be included in the concept.

text: Theorists

text: believe that creating a concept includes learning the distinct features and characteristics that are present in all examples of a concept. A good way to know if something is part of a concept is to identify the defining features of the concept and see if the object or event in question shares those defining features. For example, an animal must eat food, a plant must grow, and a vertebrate must have a spine. So, every example of an animal must have the defining feature or eating food, every plant must grow, and every vertebrate must have a spine to be included in the concept.

text: Trabecular cartilages (trabeculae cranii, sometimes simply trabeculae) are paired, rod-shaped cartilages, which develop in the head of the vertebrate embryo. They are the primordia of the anterior part of the cranial base, and are derived from the cranial neural crest cells.

text: Trabecular cartilages (trabeculae cranii, sometimes simply trabeculae) are paired, rod-shaped cartilages, which develop in the

text: head

text: of the

text: vertebrate

text: embryo

text: . They are the primordia of the anterior part of the

text: cranial base

text: , and are derived from the

text: cranial neural crest cells

text: Many other regulatory systems are involved in the transition of cartilage to bone and in bone maintenance. A particularly important bone-targeted hormonal regulator is parathyroid hormone (PTH). Parathyroid hormone is a protein made by the parathyroid gland under the control of serum calcium activity. PTH also has important systemic functions, including to keep serum calcium concentrations nearly constant regardless of calcium intake. Increasing dietary calcium results in minor increases in blood calcium. However, this is not a significant mechanism supporting osteoblast bone formation, except in the condition of low dietary calcium; further, abnormally high dietary calcium raises the risk of serious health consequences not directly related to bone mass including heart attack and stroke. Intermittent PTH stimulation increases osteoblast activity, although PTH is bifunctional and mediates bone matrix degradation at higher concentrations.

text: Many other regulatory systems are involved in the transition of cartilage to bone and in bone maintenance. A particularly important bone-targeted hormonal regulator is

text: parathyroid hormone

text: (PTH). Parathyroid hormone is a protein made by the

text: parathyroid

text: gland under the control of serum calcium activity. PTH also has important systemic functions, including to keep serum calcium concentrations nearly constant regardless of calcium intake. Increasing dietary calcium results in minor increases in blood calcium. However, this is not a significant mechanism supporting osteoblast bone formation, except in the condition of low dietary calcium; further, abnormally high dietary calcium raises the risk of serious health consequences not directly related to bone mass including

text: heart attack

text: and

text: stroke

text: . Intermittent PTH stimulation increases osteoblast activity, although PTH is bifunctional and mediates bone matrix degradation at higher concentrations.

text: Some other animals, usually, but not always, predatory animals, have their two eyes positioned on the front of their heads, thereby allowing for binocular vision and reducing their field of view in favor of stereopsis. However, eyes on the front is a highly evolved trait in vertebrates, and there are only three extant groups of vertebrates with truly forward-facing eyes: primates, carnivorous mammals, and birds of prey.

text: Some other animals, usually, but not always,

text: predatory

text: animals, have their two eyes positioned on the front of their heads, thereby allowing for binocular vision and reducing their field of view in favor of

text: stereopsis

text: . However, eyes on the front is a highly evolved trait in vertebrates, and there are only three extant groups of vertebrates with truly forward-facing eyes:

text: primate

text: s,

text: carnivorous mammals

text: , and

text: birds of prey

text: Cancellous bone has a higher surface area to mass ratio than cortical bone because it is less dense. This gives it softer, weaker, and more flexible characteristics. The greater surface area in comparison with cortical bone makes cancellous bone suitable for metabolic activity e.g. exchange of calcium ions. Cancellous bone is typically found at the ends of long bones, proximal to joints and within the interior of vertebrae. Cancellous bone is highly vascular and frequently contains red bone marrow where haematopoiesis, the production of blood cells, occurs. The primary anatomical and functional unit of cancellous bone is the trabecula. The trabeculae within cancellous bone are aligned towards the mechanical load distribution that a bone experiences within long bones such as the human femur.  As far as short bones are concerned, trabecular alignment has been studied in the vertebral pedicle. The macroscopic  yield strength of cancellous bone has also been investigated, using high resolution computer models.

text: Cancellous bone has a higher

text: surface area to mass ratio

text: than

text: cortical bone

text: because it is less dense. This gives it softer, weaker, and more flexible characteristics. The greater surface area in comparison with cortical bone makes cancellous bone suitable for metabolic activity e.g. exchange of calcium ions. Cancellous bone is typically found at the ends of long bones, proximal to joints and within the interior of vertebrae. Cancellous bone is highly

text: vascular

text: and frequently contains red

text: bone marrow

text: where

text: haematopoiesis

text: , the production of blood cells, occurs. The primary anatomical and functional unit of cancellous bone is the

text: trabecula

text: . The

text: trabeculae

text: within

text: cancellous

text: bone are aligned towards the mechanical load distribution that a bone experiences within long bones such as the human

text: femur

text: .  As far as short bones are concerned, trabecular alignment has been studied in the

text: vertebral

text: pedicle

text: . The macroscopic

text: yield

text: strength of cancellous bone has also been investigated, using high resolution computer models.

text: Homeothermy and poikilothermy refer to how stable an organism's temperature is.  Most endothermic organisms are homeothermic, like mammals.  However, animals with facultative endothermy are often poikilothermic, meaning their temperature can vary considerably.  Similarly, most fish are ectotherms, as all of their heat comes from the surrounding water. However, most are homeotherms because their temperature is very stable.

text: Homeothermy

text: and

text: poikilothermy

text: refer to how stable an organism's temperature is.  Most

text: endothermic

text: organisms are homeothermic, like

text: mammal

text: s.  However, animals with facultative

text: endothermy

text: are often poikilothermic, meaning their temperature can vary considerably.  Similarly, most fish are

text: ectotherm

text: s, as all of their heat comes from the surrounding water. However, most are homeotherms because their temperature is very stable.

text: These fish have descended from a sluggish demersal ancestor. The cold, well-mixed, oxygen-rich waters of the Southern Ocean provided an environment where a fish with a low metabolic rate could survive even without hemoglobin—albeit less efficiently. During the mid-Tertiary period, a species crash in the Southern Ocean opened up wide range of empty niches to colonize. Despite the hemoglobin-less mutants being less fit, the lack of competition allowed even the mutants to leave descendants that colonized empty habitats and evolved compensations for their mutations. Later, the periodic openings of fjords created habitats that were colonized by a few individuals. These conditions may have allowed for the loss of myoglobin.

text: These fish have descended from a sluggish

text: demersal

text: ancestor. The cold, well-mixed, oxygen-rich waters of the Southern Ocean provided an environment where a fish with a low metabolic rate could survive even without hemoglobin—albeit less efficiently. During the mid-

text: Tertiary

text: period, a species crash in the Southern Ocean opened up wide range of empty

text: niche

text: s to colonize. Despite the hemoglobin-less mutants being less fit, the lack of competition allowed even the mutants to leave descendants that colonized empty habitats and evolved compensations for their mutations. Later, the periodic openings of fjords created habitats that were colonized by a few individuals. These conditions may have allowed for the loss of myoglobin.

text: The reproduction of Osedax japonicus has been studied. Female worms reach maturity at about six weeks. They secrete mucus to form a tube that surrounds their trunk. Male worms are minute by comparison with the females and they take up residence inside the tubes. The females spawn eggs and retain them in the mucus where they are fertilised by the males. Here they develop for a time before they swim out of the mucus as trochophore larvae. The larvae are then planktonic and can live for at least ten days in the open sea. It seems that if they settle on a suitable vertebrate bone they will develop into female worms but if mature females are already present on the bone, they will develop into males. The vast majority will fail to find any sunken bone.

text: The reproduction of Osedax japonicus has been studied. Female worms reach maturity at about six weeks. They secrete

text: mucus

text: to form a tube that surrounds their trunk. Male worms are minute by comparison with the females and they take up residence inside the tubes. The females spawn eggs and retain them in the mucus where they are fertilised by the males. Here they develop for a time before they swim out of the mucus as

text: trochophore

text: larvae. The larvae are then

text: plankton

text: ic and can live for at least ten days in the open sea. It seems that if they settle on a suitable vertebrate bone they will develop into female worms but if mature females are already present on the bone, they will develop into males. The vast majority will fail to find any sunken bone.

text: Q10 (temperature coefficient), the factor by which a rate increases at a 10 °C increase in temperature, is used to measure how organisms’ performance relies on temperature.  Most have increased rates as water becomes warmer, but some have limits to this and others find ways to alter such effects, such as by endothermy or earlier recruitment of faster muscle.

text: Q10 (temperature coefficient)

text: , the factor by which a rate increases at a 10 °C increase in temperature, is used to measure how organisms’ performance relies on temperature.  Most have increased rates as water becomes warmer, but some have limits to this and others find ways to alter such effects, such as by endothermy or earlier recruitment of faster muscle.

text: variety (botany) – Vertebrate paleontology (a.k.a. vertebrate paleobiology or paleozoology) – viral evolution – The Voyage of the Beagle – vestigiality

text: variety (botany)

text: Vertebrate paleontology

text: (a.k.a. vertebrate paleobiology or paleozoology) –

text: viral evolution

text: The Voyage of the Beagle

text: vestigiality

text: In a study of early jawed vertebrate relationships, Davis et al. (2012) found acanthodians to be split among the two major clades Osteichthyes (bony fish) and Chondrichthyes (cartilaginous fish). The well-known acanthodian Acanthodes was placed within Osteichthyes, despite the presence of many chondrichthyan characteristics in its braincase. However, a newly described Silurian placoderm, Entelognathus, which has jaw anatomy shared with bony fish and tetrapods, has led to revisions of this phylogeny: acanthodians are now considered to be a paraphyletic assemblage leading to cartilaginous fish, while bony fish evolved from placoderm ancestors.

text: In a study of early jawed vertebrate relationships, Davis et al. (2012) found acanthodians to be split among the two major clades

text: Osteichthyes

text: (bony fish) and

text: Chondrichthyes

text: (cartilaginous fish). The well-known acanthodian

text: Acanthodes

text: was placed within Osteichthyes, despite the presence of many chondrichthyan characteristics in its braincase. However, a newly described Silurian

text: placoderm

text: Entelognathus

text: , which has jaw anatomy shared with

text: bony fish

text: and

text: tetrapod

text: s, has led to revisions of this phylogeny: acanthodians are now considered to be a paraphyletic assemblage leading to cartilaginous fish, while bony fish evolved from placoderm ancestors.

text: Jaws probably originated in the pharyngeal arches supporting the gills of jawless fish. The earliest jaws appeared in the now extinct placoderms and spiny sharks  during the Silurian, about 430 million years ago. The original selective advantage offered by the jaw was probably not related to feeding, but to increased respiration efficiency — the jaws were used in the buccal pump to pump water across the gills.  The familiar use of jaws for feeding would then have developed as a secondary function before becoming the primary function in many vertebrates.  All vertebrate jaws, including the human jaw, evolved from early fish jaws. The appearance of the early vertebrate jaw has been described as "perhaps the most profound and radical evolutionary step in the vertebrate history". Fish without jaws had more difficulty surviving than fish with jaws, and most jawless fish became extinct.

text: Jaws probably originated in the

text: pharyngeal arch

text: es supporting the

text: gills

text: of

text: jawless fish

text: . The earliest jaws appeared in the now extinct

text: placoderm

text: s and

text: spiny shark

text: s  during the

text: Silurian

text: , about 430 million years ago. The original selective advantage offered by the jaw was probably not related to feeding, but to increased respiration efficiency — the jaws were used in the

text: buccal pump

text: to pump water across the gills.  The familiar use of jaws for feeding would then have developed as a secondary function before becoming the primary function in many vertebrates.  All vertebrate jaws, including the human jaw, evolved from early fish jaws. The appearance of the early vertebrate jaw has been described as "perhaps the most profound and radical evolutionary step in the vertebrate history".

text: Fish without jaws

text: had more difficulty surviving than fish with jaws, and most jawless fish became extinct.

text: M. greyii is one of a small number of vertebrate species that are known to reproduce by parthenogenesis.

text: M. greyii is one of a small number of

text: vertebrate

text: species that are known to reproduce by

text: parthenogenesis

text: Cam impingement is created by the abnormal development of the femoral head-neck junction causing what has previously been described as a 'pistol-grip deformity'. This type of deformity is characterised by varying amounts of abnormal bone on the anterior and superior femoral neck at the head-neck junction (see fig. 6). The head-neck junction is at the base of the ball of the hip, where it joins the short neck, which in turn carries on downwards into the femur, or thighbone, itself. A bony protrusion or bump at the head-neck junction has been likened to a cam, an eccentric part of a rotating device. This leads to joint damage as a result of the non-spherical femoral head being forced into the acetabulum mainly with flexion and/or internal rotation. This may impart compression and shear forces to the articular cartilage, and may lead to labral tears and peeling away of the articular cartilage from the underlying bone, so-called cartilage delamination (see fig. 8).

text: On May 11, 1940 she arrived in New York, where almost immediately after, she moved to Massachusetts to take a position at the Harvard Museum of Comparative Zoology, where she published her second seminal work, The Evolution of the Horse Brain in 1948, three years after becoming a citizen of the U.S. She took leave from Harvard for the 1944-1945 academic year to be a professor of comparative anatomy at Wellesley College, a position she resigned after her hearing deteriorated severely. Edinger's work on fossil horse brains showed that evolution was a branching process, as structures could evolve independently, such as the large forebrain found in advanced mammals. This challenged the prevailing theory of the time, anagenesis, and led to the modern understanding of cladogenesis. In 1963 and 1964, Edinger was elected the president of the Society of Vertebrate Paleontology, reflecting her prominence in the field. Tilly bones, thickened bones on the vertebral columns of some fish species, are named in honor of her.

text: On May 11, 1940 she arrived in New York, where almost immediately after, she moved to

text: Massachusetts

text: to take a position at the

text: Harvard Museum of Comparative Zoology

text: , where she published her second seminal work, The Evolution of the Horse Brain in 1948, three years after becoming a citizen of the U.S. She took leave from Harvard for the 1944-1945 academic year to be a professor of

text: comparative anatomy

text: at

text: Wellesley College

text: , a position she resigned after her hearing deteriorated severely. Edinger's work on fossil horse brains showed that evolution was a branching process, as structures could evolve independently, such as the large

text: forebrain

text: found in advanced mammals. This challenged the prevailing theory of the time,

text: anagenesis

text: , and led to the modern understanding of

text: cladogenesis

text: . In 1963 and 1964, Edinger was elected the president of the

text: Society of Vertebrate Paleontology

text: , reflecting her prominence in the field. Tilly bones, thickened bones on the

text: vertebral column

text: s of some fish species, are named in honor of her.

text: A complete Basilosaurus skeleton was found in 2015, and several attempts have been made to reconstruct the vertebral column from partial skeletons.  estimated a total of 58 vertebrae, based on two partial and nonoverlapping skeletons of B. cetoides from Alabama. More complete fossils uncovered in Egypt in the 1990s allowed a more accurate estimation: the vertebral column of B. isis has been reconstructed from three overlapping skeletons to a total of 70 vertebrae with a vertebral formula interpreted as seven cervical, 18 thoracic, 20 lumbar and sacral, and 25 caudal vertebrae. The vertebral formula of B. cetoides can be assumed to be the same.

text: Vertebrates were once thought to be unable to perform this cycle because there was no evidence of its two key enzymes, isocitrate lyase and malate synthase. However, some research suggests that this pathway may exist in some, if not all, vertebrates.  Specifically, some studies show evidence of components of the glyoxylate cycle existing in significant amounts in the liver tissue of chickens. Data such as these support the idea that the cycle could theoretically occur in even the most complex vertebrates. Other experiments have also provided evidence that the cycle is present among certain insect and marine invertebrate species, as well as strong evidence of the cycle's presence in nematode species. However, other experiments refute this claim  Some publications conflict on the presence of the cycle in mammals: for example, one paper has stated that the glyoxalate cycle is active in hibernating bears, but this report was disputed in a later paper. Evidence exists for malate synthase activity in humans due to a dual functional malate/B-methylmalate synthase of mitochondrial origin called CLYBL expressed in brown fat and kidney. Vitamin D may regulate this pathway in vertebrates.

text: Vertebrates were once thought to be unable to perform this cycle because there was no evidence of its two key

text: enzyme

text: s, isocitrate lyase and malate synthase. However, some research suggests that this pathway may exist in some, if not all, vertebrates.  Specifically, some studies show evidence of components of the glyoxylate cycle existing in significant amounts in the liver tissue of chickens. Data such as these support the idea that the cycle could theoretically occur in even the most complex vertebrates. Other experiments have also provided evidence that the cycle is present among certain insect and marine invertebrate species, as well as strong evidence of the cycle's presence in nematode species. However, other experiments refute this claim  Some publications conflict on the presence of the cycle in

text: mammal

text: s: for example, one paper has stated that the glyoxalate cycle is active in hibernating bears, but this report was disputed in a later paper. Evidence exists for malate synthase activity in humans due to a dual functional malate/B-methylmalate synthase of mitochondrial origin called CLYBL expressed in brown fat and kidney. Vitamin D may regulate this pathway in vertebrates.

text: The Eilat virus shows an evolutionary change which may have occurred to alphaviruses. Normally, an alphavirus similar to that of the EILV would use mosquitoes as the vector of transmission to other (usually vertebrates) creatures. However, the Eilat virus can replicate consummately in an insect host and fails completely to even enter the cells of vertebrates. Based on experimental evidence when a relativity similar virus (SINV) was injected into vertebrate cell lines , the cells showed to have a great cytopathic effect. While when the same test was done on the EILV, the virus showed no cytopathic effect on the vertebrate cell lines.  Therefore, evolutionary  these results aid in suggesting that EILV lost its capability in infecting vertebrate cells. Thus, EILV appears to be mosquito-specific and represents a previously undescribed complex within the genus Alphavirus. Reverse genetic studies of EILV may help in  the discovery of determinants of alphavirus host range which balances disease emergence.

text: The Eilat virus shows an evolutionary change which may have occurred to alphaviruses. Normally, an alphavirus similar to that of the EILV would use mosquitoes as the vector of transmission to other (usually vertebrates) creatures. However, the Eilat virus can replicate consummately in an insect host and fails completely to even enter the cells of vertebrates. Based on experimental evidence when a relativity similar virus (SINV) was injected into vertebrate cell lines , the cells showed to have a great

text: cytopathic

text: effect. While when the same test was done on the EILV, the virus showed no

text: cytopathic

text: effect on the vertebrate cell lines.  Therefore, evolutionary  these results aid in suggesting that EILV lost its capability in infecting vertebrate cells. Thus, EILV appears to be mosquito-specific and represents a previously undescribed complex within the genus Alphavirus. Reverse genetic studies of EILV may help in  the discovery of determinants of alphavirus host range which balances disease emergence.

text: There are 316 species of vertebrates within the region, including:

text: These genes were first shown to be arranged into a physically-linked chromosomal cluster in amphioxus, an invertebrate with a single member of each of the three gene families. All the ParaHox genes in the amphioxus genome are therefore in the ParaHox gene cluster. In contrast, the human genome has six ParaHox genes (GSX1, GSX2, PDX1, CDX1, CDX2, CDX4), of which three genes (GSX1, PDX1 (=IPF1), CDX2) are physically linked to form a human ParaHox gene cluster on chromosome 13. Mouse has a homologous ParaHox gene cluster on chromosome 5. The other three human ParaHox genes are remnants from duplicated ParaHox gene clusters that were generated in the 2R genome duplications at the base of vertebrate evolution. Some vertebrates, notably chondrichthyan fish and coelacanths, have retained an additional ParaHox gene (PDX2).

text: These genes were first shown to be arranged into a physically-linked chromosomal cluster in

text: amphioxus

text: , an

text: invertebrate

text: with a single member of each of the three gene families. All the ParaHox genes in the amphioxus genome are therefore in the ParaHox gene cluster. In contrast, the human genome has six ParaHox genes (

text: ), of which three genes (

text: ) are physically linked to form a human ParaHox gene cluster on

text: chromosome 13

text: . Mouse has a homologous ParaHox gene cluster on chromosome 5. The other three human ParaHox genes are remnants from duplicated ParaHox gene clusters that were generated in the

text: genome duplications

text: at the base of vertebrate evolution. Some vertebrates, notably

text: chondrichthyan

text: fish and

text: coelacanths

text: , have retained an additional ParaHox gene (PDX2).

text: Humans have 24 ribs (12 pairs). The first seven sets of ribs, known as "true ribs" (costae verae) also known as vertebrosternal ribs, are directly attached to the sternum through the costal cartilage. Rib 1 is unique and harder to distinguish than other ribs.  It is a short, flat, C-shaped bone.  The vertebral attachment can be found just below the neck and the majority of this bone can be found above the level of the clavicle.  Ribs 2 through 7 have a more traditional appearance and become longer and less curved as they progress downwards.  The following five sets are known as "false ribs" (costae spuriae), three of these sharing a common cartilaginous connection to the sternum, while the last two (eleventh and twelfth ribs) are termed floating ribs (costae fluctuantes) or vertebral ribs. They are attached to the vertebrae only, and not to the sternum or cartilage coming off of the sternum. Some people lack one of the two pairs of floating ribs, while others have a third pair.

text: Humans have 24 ribs (12 pairs). The first seven sets of ribs, known as "

text: true ribs

text: " (costae verae) also known as vertebrosternal ribs, are directly attached to the

text: sternum

text: through the

text: costal cartilage

text: . Rib 1 is unique and harder to distinguish than other ribs.  It is a short, flat, C-shaped bone.  The vertebral attachment can be found just below the

text: neck

text: and the majority of this bone can be found above the level of the

text: clavicle

text: .  Ribs 2 through 7 have a more traditional appearance and become longer and less curved as they progress downwards.  The following five sets are known as "

text: false ribs

text: " (costae spuriae), three of these sharing a common cartilaginous connection to the sternum, while the last two (eleventh and twelfth ribs) are termed

text: floating rib

text: s (costae fluctuantes) or vertebral ribs. They are attached to the vertebrae only, and not to the sternum or cartilage coming off of the sternum. Some people lack one of the two pairs of floating ribs, while others have a third pair.

text: The evolution of multicellularity brought about various challenges, many of which could be met by increasingly sophisticated innate immune systems, but which also served as an evolutionary driving force for the development of adaptive immune systems. The adaptive or "specific" immune system in its fully qualified form (i.e. based on major histocompatibility complex (MHC), T-cell receptors (TCR), and antibodies) exists only in jawed vertebrates, but an independently evolved adaptive immune system has been identified in hagfish and lampreys (non-jawed vertebrates).

text: The evolution of

text: multicellularity

text: brought about various challenges, many of which could be met by increasingly sophisticated innate immune systems, but which also served as an evolutionary driving force for the development of

text: adaptive immune system

text: s. The adaptive or "specific" immune system in its fully qualified form (i.e. based on

text: major histocompatibility complex

text: (MHC),

text: T-cell receptor

text: s (TCR), and

text: antibodies

text: ) exists only in

text: jawed vertebrate

text: s, but an independently evolved adaptive immune system has been identified in

text: hagfish

text: and

text: lamprey

text: s (non-jawed vertebrates).

text: The branching order suggests that Alloherpesviridae is the basal clade and that Herpesviridae and Malacoherpesviridae are sister clades. Given the phylogenetic distances between vertebrates and molluscs, this suggests that herpesviruses were initially fish viruses and that they have evolved with their hosts to infect other vertebrates.

text: The

text: branching order

text: suggests that Alloherpesviridae is the basal

text: clade

text: and that Herpesviridae and Malacoherpesviridae are sister clades. Given the phylogenetic distances between vertebrates and molluscs, this suggests that herpesviruses were initially fish viruses and that they have evolved with their hosts to infect other vertebrates.

text: Because ectotherms depend on environmental conditions for body temperature regulation, as a rule they are more sluggish at night and in early mornings. When they emerge from shelter, many diurnal ectotherms need to heat up in the early sunlight before they can begin their daily activities. In cool weather the foraging activity of such species is therefore restricted to the day time in most vertebrate ectotherms, and in cold climates most cannot survive at all. In lizards, for instance, most nocturnal species are geckos specialising in "sit and wait" foraging strategies. Such strategies do not require as much energy as active foraging, and do not as a rule require hunting activity of the same intensity. From another point of view, sit-and-wait predation may require very long periods of unproductive waiting. Endotherms cannot in general afford such long periods without food, but suitably adapted ectotherms can wait without expending much energy. Endothermic vertebrate species are therefore less dependent on the environmental conditions and have developed a higher variability (both within and between species) in their daily patterns of activity.

text: Because ectotherms depend on environmental conditions for body temperature regulation, as a rule they are more sluggish at night and in early mornings. When they emerge from shelter, many

text: diurnal

text: ectotherms need to heat up in the early sunlight before they can begin their daily activities. In cool weather the foraging activity of such species is therefore restricted to the day time in most vertebrate ectotherms, and in cold climates most cannot survive at all. In lizards, for instance, most

text: nocturnal

text: species are geckos specialising in

text: "sit and wait"

text: foraging strategies. Such strategies do not require as much energy as active foraging, and do not as a rule require hunting activity of the same intensity. From another point of view, sit-and-wait predation may require very long periods of unproductive waiting. Endotherms cannot in general afford such long periods without food, but suitably adapted ectotherms can wait without expending much energy. Endothermic vertebrate species are therefore less dependent on the environmental conditions and have developed a higher variability (both within and between species) in their daily patterns of activity.

text: One of the people who helped figure out the vertebrate progression was French zoologist Georges Cuvier (1769–1832), who realized that fossils found in older rock strata differed greatly from more recent fossils or modern animals.  He published his findings in 1812 and, although he steadfastly refuted evolution, his work proved the (at the time) contested theory of extinction of species.

text: One of the people who helped figure out the vertebrate progression was French zoologist

text: Georges Cuvier

text: (1769–1832), who realized that fossils found in older rock strata differed greatly from more recent fossils or modern animals.  He published his findings in 1812 and, although he steadfastly refuted

text: evolution

text: , his work proved the (at the time) contested theory of

text: extinction

text: of species.

text: Paleontological evidence shows that the ancestors of living crocodilians were active and endothermic (warm-blooded). Some experts believe that their archosaur ancestors were warm-blooded as well. Physiological, anatomical, and developmental features of the crocodilian heart support the paleontological evidence and show that the lineage reverted to ectothermy when it invaded the aquatic, ambush predator niche. Crocodilian embryos develop fully 4-chambered hearts at an early stage. Modifications to the growing heart form a pulmonary bypass shunt that includes the left aortic arch, which originates from the right ventricle, the foramen of Panizza between the left and right aortic arches, and the cog‐tooth valve at the base of the pulmonary artery. The shunt is used during diving to make the heart function as 3-chambered heart, providing the crocodilian with the neurally controlled shunting used by ectotherms. The researchers concluded that the ancestors of living crocodilians had fully 4-chambered hearts, and were therefore warm-blooded, before they reverted to a cold-blooded or ectothermic metabolism. The authors also provide other evidence for endothermy in stem archosaurs. It is reasonable to suggest that later crocodilians developed the pulmonary bypass shunt as they became cold-blooded, aquatic, and less active.

text: Paleontological evidence shows that the ancestors of living crocodilians were active and endothermic (warm-blooded). Some experts believe that their archosaur ancestors were warm-blooded as well. Physiological, anatomical, and developmental features of the crocodilian heart support the paleontological evidence and show that the lineage reverted to ectothermy when it invaded the aquatic, ambush predator niche. Crocodilian embryos develop fully 4-chambered hearts at an early stage. Modifications to the growing heart form a pulmonary bypass shunt that includes the left

text: aortic arch

text: , which originates from the right

text: ventricle

text: , the

text: foramen of Panizza

text: between the left and right aortic arches, and the cog‐tooth valve at the base of the

text: pulmonary artery

text: . The shunt is used during diving to make the heart function as 3-chambered heart, providing the crocodilian with the neurally controlled shunting used by ectotherms. The researchers concluded that the ancestors of living crocodilians had fully 4-chambered hearts, and were therefore warm-blooded, before they reverted to a cold-blooded or ectothermic metabolism. The authors also provide other evidence for endothermy in stem archosaurs. It is reasonable to suggest that later crocodilians developed the pulmonary bypass shunt as they became cold-blooded, aquatic, and less active.

text: Most studies consider dinosaurs as endothermic (warm-blooded) animals, with an elevated metabolism comparable to that of today's mammals and birds. In a 2009 study, Herman Pontzer and colleagues calculated the aerobic endurance of various dinosaurs. Even at moderate running speeds, Heterodontosaurus would have exceeded the maximum aerobic capabilities possible for an ectotherm (cold-blooded) animal, indicating endothermy in this genus.

text: Most studies consider dinosaurs as

text: endothermic

text: (warm-blooded) animals, with an elevated

text: metabolism

text: comparable to that of today's mammals and birds. In a 2009 study, Herman Pontzer and colleagues calculated the

text: aerobic endurance

text: of various dinosaurs. Even at moderate running speeds, Heterodontosaurus would have exceeded the maximum aerobic capabilities possible for an

text: ectotherm

text: (cold-blooded) animal, indicating endothermy in this genus.

text: The debate between Haeckel and His ultimately becomes fueled by the description of an embryo that Wilhelm Krause propels directly into the ongoing feud between Haeckel and His.  Haeckel speculates that the allantois is formed in a similar way in both humans and other mammals.  His, on the other hand, accuses Haeckel of altering and playing with the facts.  Although Haeckel is proven right about the allantois, the utilization of Krause’s embryo as justification turns out to be problematic, for the embryo is that of a bird rather than a human.  The underlying debate between Haeckel and His derives from differing viewpoints regarding the similarity or dissimilarity of vertebrate embryos.  In response to Haeckel’s evolutionary claim that all vertebrates are essentially identical in the first month of embryonic life as proof of common descent, His responds by insisting that a more skilled observer would recognize even sooner that early embryos can be distinguished.  His also counteracts Hacekel’s sequence of drawings in the Anthropogenie with what he refers to as “exact” drawings, highlighting specific differences.  Ultimately, His goes so far as to accuse Haeckel of “faking” his embryo illustrations to make the vertebrate embryos appear more similar than in reality.  His also accuses Haeckel of creating early human embryos that he conjured in his imagination rather than obtained through empirical observation.  His completes his denunciation of Haeckel by pronouncing that Haeckel had “‘relinquished the right to count as an equal in the company of serious researchers.’”

text: The debate between Haeckel and His ultimately becomes fueled by the description of an embryo that

text: Wilhelm Krause

text: propels directly into the ongoing feud between Haeckel and His.  Haeckel speculates that the

text: allantois

text: is formed in a similar way in both humans and other mammals.  His, on the other hand, accuses Haeckel of altering and playing with the facts.  Although Haeckel is proven right about the allantois, the utilization of Krause’s embryo as justification turns out to be problematic, for the embryo is that of a bird rather than a human.  The underlying debate between Haeckel and His derives from differing viewpoints regarding the similarity or dissimilarity of vertebrate embryos.  In response to Haeckel’s evolutionary claim that all vertebrates are essentially identical in the first month of embryonic life as proof of common descent, His responds by insisting that a more skilled observer would recognize even sooner that early embryos can be distinguished.  His also counteracts Hacekel’s sequence of drawings in the Anthropogenie with what he refers to as “exact” drawings, highlighting specific differences.  Ultimately, His goes so far as to accuse Haeckel of “faking” his embryo illustrations to make the vertebrate embryos appear more similar than in reality.  His also accuses Haeckel of creating early human embryos that he conjured in his imagination rather than obtained through

text: empirical

text: observation.  His completes his denunciation of Haeckel by pronouncing that Haeckel had “‘relinquished the right to count as an equal in the company of serious researchers.’”

text: A limbus vertebra also see vertebral epophysis  is a bone trauma in the vertebral body bearing a radiographic similarity to a vertebral fracture. The anterior-superior corner of a single vertebra is the common site for this defect although it can also be seen at the inferior corner as well as the posterior or anterior margin.  Anatomically, it is assumed to be an intra-vertebral body herniation of the disc material occurring during adolescent growt spurt when the ring apophysis has not yet fused. It was first described by Schmorl in 1927 and later in detail by Leif Sward and Adad baranto.

text: The branching order among the herpesviruses suggests that Alloherpesviridae is the basal clade and that Herpesviridae and Malacoherpesviridae are sister clades. Given the phylogenetic distances between vertebrates and molluscs this suggests that herpesviruses were initially fish viruses and that they have evolved with their hosts to infect other vertebrates.

text: ‘Ancient asexuals’: Bdelloid rotifers are assumed to have reproduced without sex for many millions of years. Males are absent within the species, and females reproduce only by parthenogenesis.

text: ‘Ancient asexuals’:

text: Bdelloid

text: rotifers are assumed to have reproduced without sex for many millions of years. Males are absent within the species, and females reproduce only by

text: parthenogenesis

text: Because of their multi-potent capabilities, mesenchymal stem cell (MSC) lineages have been used successfully in animal models to regenerate articular cartilage and in human models to regenerate bone.  Recent research demonstrates that articular cartilage may be able to be repaired via percutaneous introduction of mesenchymal stem cells (MSC’s).

text: Like all Plasmodium species P. foleyi has both vertebrate and insect hosts. The vertebrate hosts for this parasite are mammals.

text: Like all Plasmodium species P. foleyi has both

text: vertebrate

text: and

text: insect

text: mammal

text: s.

text: The position of the SVP is that "The fossil record of vertebrates unequivocally supports the hypothesis that vertebrates have evolved through time" and that evolution is "the central organizing principle of biology, understood as descent with modification" and is important to geology as well.  The Society believes only scientifically supported evolutionary theory should be taught in school and that creationism and intelligent design have no place in the scientific curriculum. To this end, SVP has set up programs to train educators in teaching evolution and to support teachers who oppose those who desire to bring intelligent design into the classroom.

text: The position of the SVP is that "The fossil record of vertebrates unequivocally supports the hypothesis that vertebrates have evolved through time" and that evolution is "the central organizing principle of

text: biology

text: , understood as descent with modification" and is important to

text: geology

text: as well.  The Society believes only scientifically supported evolutionary theory should be taught in school and that

text: creationism

text: and

text: intelligent design

text: have no place in the scientific curriculum. To this end, SVP has set up programs to train educators in teaching evolution and to support teachers who oppose those who desire to bring intelligent design into the classroom.

text: In vertebrates, the lower jaw (mandible or jawbone) is a bone forming the skull with the cranium. In lobe-finned fishes and the early fossil tetrapods, the bone homologous to the mandible of mammals is merely the largest of several bones in the lower jaw. It is referred to as the dentary bone, and forms the body of the outer surface of the jaw. It is bordered below by a number of splenial bones, while the angle of the jaw is formed by a lower angular bone and a suprangular bone just above it. The inner surface of the jaw is lined by a prearticular bone, while the articular bone forms the articulation with the skull proper. Finally a set of three narrow coronoid bones lie above the prearticular bone. As the name implies, the majority of the teeth are attached to the dentary, but there are commonly also teeth on the coronoid bones, and sometimes on the prearticular as well.

text: In vertebrates, the lower jaw (

text: mandible

text: or jawbone) is a

text: bone

text: forming the

text: skull

text: with the cranium. In

text: lobe-finned fish

text: es and the early fossil

text: tetrapod

text: s, the bone

text: homologous

text: to the mandible of mammals is merely the largest of several bones in the lower jaw. It is referred to as the dentary bone, and forms the body of the outer surface of the jaw. It is bordered below by a number of

text: splenial

text: bones, while the angle of the jaw is formed by a lower

text: angular bone

text: and a

text: suprangular

text: bone just above it. The inner surface of the jaw is lined by a prearticular bone, while the

text: articular

text: bone forms the articulation with the skull proper. Finally a set of three narrow coronoid bones lie above the prearticular bone. As the name implies, the majority of the teeth are attached to the dentary, but there are commonly also teeth on the coronoid bones, and sometimes on the prearticular as well.

text: The vertebral column of humans takes a forward bend in the lumbar (lower) region and a backward bend in the thoracic (upper) region.  Without the lumbar curve, the vertebral column would always lean forward, a position that requires much more muscular effort for bipedal animals.  With a forward bend, humans use less muscular effort to stand and walk upright.  Together the lumbar and thoracic curves bring the body's center of gravity directly over the feet.  Also, the degree of body erection (the angle of body incline to a vertical line in a walking cycle) is significantly smaller to conserve energy.

text: Like all Plasmodium species P. wenyoni has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. wenyoni has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: The perichondrium (from Greek περί (peri 'around') and χόνδρος (chondros 'cartilage')) is a layer of dense irregular connective tissue that surrounds the cartilage of developing bone. It consists of two separate layers: an outer fibrous layer and inner chondrogenic layer. The fibrous layer contains fibroblasts, which produce collagenous fibers.  The chondrogenic layer remains undifferentiated and can form chondroblasts or chondrocytes. Perichondrium can be found around the perimeter of elastic cartilage and hyaline cartilage. Fibrocartilage and articular cartilage both lack perichondrium.

text: The perichondrium (from

text: Greek

text: περί (peri 'around') and χόνδρος (chondros 'cartilage')) is a layer of

text: dense irregular connective tissue

text: that surrounds the

text: cartilage

text: of developing bone. It consists of two separate layers: an outer fibrous layer and inner

text: chondrogenic

text: layer. The fibrous layer contains

text: fibroblasts

text: , which produce

text: collagenous fibers

text: .  The chondrogenic layer remains undifferentiated and can form

text: chondroblasts

text: or

text: chondrocytes

text: . Perichondrium can be found around the perimeter of

text: elastic cartilage

text: and

text: hyaline cartilage

text: Fibrocartilage

text: and

text: articular cartilage

text: both lack perichondrium.

text: An X-ray is essential for the proper diagnosis of a malunion. The doctor will look into the patient’s history and the treatment process for the bone fracture. Oftentimes a CT scan and probably a MRI are also used in diagnosis. MRI are used to check of cartilage and ligament issues that developed due to the malunion and misalignment. CT scans are used to locate normal or abnormal structures within the body and to help during procedures to guide the placement of instruments and/or treatments.

text: An

text: X-ray

text: is essential for the proper diagnosis of a malunion. The doctor will look into the patient’s history and the treatment process for the bone fracture. Oftentimes a

text: CT scan

text: and probably a

text: MRI

text: are also used in diagnosis.

text: MRI

text: are used to check of cartilage and ligament issues that developed due to the malunion and misalignment.

text: CT scans

text: are used to locate normal or abnormal structures within the body and to help during procedures to guide the placement of instruments and/or treatments.

text: Brian Keith Hall  (born, 1941) is the George S. Campbell Professor of Biology and University Research Professor Emeritus at Dalhousie University in Halifax, Nova Scotia.  Professor Hall has researched and extensively written on bone and cartilage formation in developing vertebrate embryos. He is an active participant in the evolutionary developmental biology (EVO-DEVO) debate on the nature and mechanisms of animal body plan formation.  Professor Hall has proposed that the neural crest tissue of vertebrates may be viewed as a fourth embryonic germ layer.  As such, the neural crest - in Hall's view - plays a role equivalent to that of the endoderm, mesoderm, and ectoderm of bilaterian development and is a definitive feature of vertebrates (as hypothesized by Gans and Northcutt[1983]).  As such, vertebrates are the only quadroblastic, rather than triploblastic bilaterian animals.  In vertebrates the neural crest serves to integrate the somatic division (derived from ectoderm and mesoderm) and visceral division (derived from endoderm and mesoderm) together via a wide range novel vertebrate tissues (bone, cartilage, sympathetic nervous system, etc...).

text: Brian Keith Hall  (born, 1941) is the George S. Campbell Professor of Biology and University Research Professor Emeritus at Dalhousie University in

text: Halifax, Nova Scotia

text: .  Professor Hall has researched and extensively written on

text: bone

text: and

text: cartilage

text: formation in developing vertebrate embryos. He is an active participant in the

text: evolutionary developmental biology

text: (EVO-DEVO) debate on the nature and mechanisms of animal

text: body plan

text: formation.  Professor Hall has proposed that the

text: neural crest

text: tissue of

text: vertebrates

text: may be viewed as a fourth embryonic

text: germ layer

text: .  As such, the neural crest - in Hall's view - plays a role equivalent to that of the

text: endoderm

text: mesoderm

text: , and

text: ectoderm

text: of

text: bilaterian

text: development and is a definitive feature of vertebrates (as hypothesized by

text: Gans and Northcutt

text: [1983]).  As such, vertebrates are the only

text: quadroblastic

text: , rather than

text: triploblastic

text: bilaterian animals.  In vertebrates the neural crest serves to integrate the

text: somatic

text: division (derived from ectoderm and mesoderm) and

text: visceral

text: division (derived from endoderm and mesoderm) together via a wide range novel vertebrate tissues (bone, cartilage, sympathetic nervous system, etc...).

text: In their paper Andrikou and Arnone argue that to truly understand the evolution of muscle cells the function of transcriptional regulators must be understood in the context of other external and internal interactions. Through their analysis, Andrikou and Arnone found that there were conserved orthologues of the gene regulatory network in both invertebrate bilaterians and in cnidarians. They argue that having this common, general regulatory circuit allowed for a high degree of divergence from a single well functioning network. Andrikou and Arnone found that the orthologues of genes found in vertebrates had been changed through different types of structural mutations in the invertebrate deuterostomes and protostomes, and they argue that these structural changes in the genes allowed for a large divergence of muscle function and muscle formation in these species. Andrikou and Arnone were able to recognize not only any difference due to mutation in the genes found in vertebrates and invertebrates but also the integration of species specific genes that could also cause divergence from the original gene regulatory network function. Thus, although a common muscle patterning system has been determined, they argue that this could be due to a more ancestral gene regulatory network being coopted several times across lineages with additional genes and mutations causing very divergent development of muscles. Thus it seems that myogenic patterning framework may be an ancestral trait. However, Andrikou and Arnone explain that the basic muscle patterning structure must also be considered in combination with the cis regulatory elements present at different times during development. In contrast with the high level of gene family apparatuses structure, Andrikou and Arnone found that the cis regulatory elements were not well conserved both in time and place in the network which could show a large degree of divergence in the formation of muscle cells. Through this analysis, it seems that the myogenic GRN is an ancestral GRN with actual changes in myogenic function and structure possibly being linked to later coopts of genes at different times and places.

text: In their paper Andrikou and Arnone argue that to truly understand the evolution of muscle cells the function of transcriptional regulators must be understood in the context of other external and internal interactions. Through their analysis, Andrikou and Arnone found that there were conserved

text: orthologues

text: cis regulatory elements

text: present at different times during development. In contrast with the high level of gene family apparatuses structure, Andrikou and Arnone found that the cis regulatory elements were not well conserved both in time and place in the network which could show a large degree of divergence in the formation of muscle cells. Through this analysis, it seems that the myogenic GRN is an ancestral GRN with actual changes in myogenic function and structure possibly being linked to later coopts of genes at different times and places.

text: The vertebrate fauna is dominated by the small basal ornithopod Oryctodromeus, which dominates the vertebrate assemblage and is known from several partial skeletons.  An ankylosaur, a Tenontosaurus-like iguanodontid, a hadrosaurid, dromaeosaurs, a tyrannosauroid, a possible neovenatorid allosauroid, a giant oviraptorosaur (represented by eggshell of the oogenus Macroelongatoolithus carleylei), indeterminate small theropods, possible neoceratopsians, large and small crocodilians, turtles, a variety of small mammals, and semionotid fish are known from very fragmentary remains.

text: The vertebrate fauna is dominated by the small basal ornithopod

text: Oryctodromeus

text: , which dominates the vertebrate assemblage and is known from several partial skeletons.  An

text: ankylosaur

text: , a

text: Tenontosaurus

text: -like

text: iguanodontid

text: , a

text: hadrosaurid

text: dromaeosaurs

text: , a

text: tyrannosauroid

text: , a possible

text: neovenatorid

text: allosauroid, a giant

text: oviraptorosaur

text: (represented by eggshell of the oogenus

text: Macroelongatoolithus

text: carleylei), indeterminate small

text: theropods

text: , possible

text: neoceratopsians

text: , large and small crocodilians, turtles, a variety of small mammals, and semionotid fish are known from very fragmentary remains.

text: Previously, L. guttatus was known to exhibit cranial endothermy, generating and maintaining metabolic heat in the cranial and optic regions to keep them 2 °C warmer than the rest of the body.  This adaptation is important for maintaining brain and eye function during the wide range of temperatures it experiences with its vertical movements.

text: All vertebrates are built along the basic chordate body plan: a stiff rod running through the length of the animal (vertebral column or notochord), with a hollow tube of nervous tissue (the spinal cord) above it and the gastrointestinal tract below.

text: All vertebrates are built along the basic chordate

text: body plan

text: : a stiff rod running through the length of the animal (vertebral column or

text: notochord

text: ), with a hollow tube of nervous tissue (the

text: spinal cord

text: ) above it and the

text: gastrointestinal tract

text: below.

text: Studies to determine the evolutionary origins of vertebrates have led to understanding the development of immune system processes and furthermore answer the questions of how and why pathogens have learned to evade and shut down these selectable genetic traits.  Eight functional and four pseudo IRG genes have been identified in the invertebrate Branchiostoma floridiae.  Li et al. determined expression patterns of functional IFN-inducible GTPase genes in Branchiostoma japonicum at various immunologic sites when induced by pathogens and pathogenic substances.  This evidence suggests that IRGs may function in an immune-related capacity in cephalochordates.  The paradox remains that these IRGs function without induction by IFN activation pathways, since B. japonicum and other amphioxus species do not possess IFN and IFN receptor genes.  It is possible that IRGs may have existed prior to the Cambrian Explosion as an innate immune mechanism and with the evolution of the adaptive immune system in vertebrates, IFN evolved to modulate IRG function.

text: Studies to determine the evolutionary origins of vertebrates have led to understanding the development of immune system processes and furthermore answer the questions of how and why pathogens have learned to evade and shut down these selectable genetic traits.  Eight functional and four pseudo IRG genes have been identified in the invertebrate

text: Branchiostoma floridiae

text: .  Li et al. determined expression patterns of functional IFN-inducible GTPase genes in

text: Branchiostoma japonicum

text: at various immunologic sites when induced by pathogens and pathogenic substances.  This evidence suggests that IRGs may function in an immune-related capacity in

text: cephalochordates

text: .  The paradox remains that these IRGs function without induction by IFN activation pathways, since B. japonicum and other

text: amphioxus

text: species do not possess IFN and IFN receptor genes.  It is possible that IRGs may have existed prior to the

text: Cambrian Explosion

text: as an innate immune mechanism and with the evolution of the adaptive immune system in vertebrates, IFN evolved to modulate IRG function.

text: Grazing can have varied effects on vertebrates. Kuhnert et al. observed that different bird species react in different ways to changes in grazing intensity. Grazing has also been thought to decrease the abundance of vertebrates, such as the prairie dog and the desert tortoise. However, Kazmaier et al. found that the effect of moderate grazing on the Texas tortoise did not show a significant difference when comparing grazed and ungrazed plots.

text: Grazing can have varied effects on vertebrates. Kuhnert et al. observed that different bird species react in different ways to changes in grazing intensity. Grazing has also been thought to decrease the abundance of vertebrates, such as the

text: prairie dog

text: and the

text: desert tortoise

text: . However, Kazmaier et al. found that the effect of moderate grazing on the

text: Texas tortoise

text: did not show a significant difference when comparing grazed and ungrazed plots.

text: Ectotherms rely largely on external heat sources such as sunlight to achieve their optimal body temperature for various bodily activities. Accordingly, they depend on ambient conditions to reach operational body temperatures. In contrast, endothermic animals as a rule maintain nearly constant high operational body temperatures largely by reliance on internal heat produced by metabolically active organs (liver, kidney, heart, brain, muscle) or even by specialized heat producing organs like brown adipose tissue (BAT). Also as a rule, ectotherms have lower metabolic rates than endotherms at a given body mass. As a consequence, endotherms generally rely on higher food consumption, and commonly on food of higher energy content. Such requirements may limit the carrying capacity of a given environment for endotherms as compared to its carrying capacity for ectotherms.

text: Ectotherms rely largely on external heat sources such as

text: sunlight

text: to achieve their optimal

text: body temperature

text: for various bodily activities. Accordingly, they depend on ambient conditions to reach operational body temperatures. In contrast,

text: endotherm

text: ic animals as a rule maintain nearly constant high operational body temperatures largely by reliance on internal heat produced by metabolically active organs (liver, kidney, heart, brain, muscle) or even by specialized heat producing organs like

text: brown adipose tissue

text: (BAT). Also as a rule, ectotherms have lower metabolic rates than

text: endotherms

text: at a given body mass. As a consequence, endotherms generally rely on higher food consumption, and commonly on food of higher energy content. Such requirements may limit the

text: carrying capacity

text: of a given environment for endotherms as compared to its carrying capacity for ectotherms.

text: Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates.

text: Within the infraphylum

text: Gnathostomata

text: , cartilaginous fishes are distinct from all other jawed vertebrates.

text: His discoveries as leader of the Siboga Expedition led him to propose Weber's line, which encloses the region in which the mammalian fauna is exclusively Australasian, as an alternative to Wallace's Line. As is the case with plant species, faunal surveys revealed that for most vertebrate groups Wallace’s line was not the most significant biogeographic boundary.  The Tanimbar Island group, and not the boundary between Bali and Lombok, appears to be the major interface between the Oriental and Australasian regions for mammals and other terrestrial vertebrate groups.

text: His discoveries as leader of the

text: Siboga Expedition

text: led him to propose Weber's line, which encloses the region in which the

text: mammalian

text: fauna

text: is exclusively

text: Australasia

text: n, as an alternative to

text: Wallace's Line

text: . As is the case with plant species, faunal surveys revealed that for most vertebrate groups Wallace’s line was not the most significant biogeographic boundary.  The

text: Tanimbar

text: Island group, and not the boundary between Bali and Lombok, appears to be the major interface between the Oriental and Australasian regions for mammals and other terrestrial vertebrate groups.

text: Williston noticed that, over evolutionary time, the modular and serially repeated parts distinguishing animal groups exhibited trends in numbers and types.  For instance, ancient vertebrates were characterized by mouths that contained mostly similar teeth, whereas recent vertebrates are characterized by mouths that contain many different teeth, adapted for biting, tearing, and compacting food; differences ultimately characterized different diets, with carnivores bearing incisors and canines and grazers bearing mostly molars.  So pronounced were these trends that Williston (1914) declared that “it is also a law in evolution that the parts in an organism tend toward reduction in number, with the fewer parts greatly specialized in function”.

text: The structure of Man: An Index to His Past History deals with various anatomical elements of the human body and attempts to frame them in an evolutionary context with other vertebrates. Wiedersheim himself suggests in the introduction that this work is in the same vein as  Thomas Huxley's earlier Evidence as to man's place in nature. The structure of Man began as a much shorter academic treatise, Der Bau der Menschen, produced in 1887 with a small intended circulation. In its original form it lacked any illustrations and gave only a brief overview of many of its topics. Thanks to a high degree of interest and correspondence regarding the work Wiedersheim decided to publish a revised and expanded version. The German second edition was published in 1893 with an English translation by Henry and Matilda Bernard following in 1895.

text: The structure of Man: An Index to His Past History deals with various anatomical elements of the human body and attempts to frame them in an evolutionary context with other vertebrates. Wiedersheim himself suggests in the introduction that this work is in the same vein as

text: Thomas Huxley's

text: earlier

text: Evidence as to man's place in nature

text: . The structure of Man began as a much shorter academic treatise, Der Bau der Menschen, produced in 1887 with a small intended circulation. In its original form it lacked any illustrations and gave only a brief overview of many of its topics. Thanks to a high degree of interest and correspondence regarding the work Wiedersheim decided to publish a revised and expanded version. The German second edition was published in 1893 with an English translation by Henry and Matilda Bernard following in 1895.

text: Homeothermy and poikilothermy refer to how stable an organism's deep-body temperature is. Most endothermic organisms are homeothermic, like mammals. However, animals with facultative endothermy are often poikilothermic, meaning their temperature can vary considerably. Most fish are ectotherms, as most of their heat comes from the surrounding water. However, almost all fish are poikilothermic.

text: Homeothermy

text: and

text: poikilothermy

text: refer to how stable an organism's deep-body temperature is. Most endothermic organisms are homeothermic, like

text: mammal

text: s. However, animals with

text: facultative endothermy

text: are often poikilothermic, meaning their temperature can vary considerably. Most

text: fish

text: are ectotherms, as most of their heat comes from the surrounding water. However, almost all fish are poikilothermic.

text: This condition is also known as arylsulfatase E deficiency, CDPX1, and X-linked recessive chondrodysplasia punctata 1. The syndrome rarely affects females, but they can be carriers of the recessive allele.  Although the exact number of people diagnosed with CDPX1 is unknown, it was estimated that 1 in 500,000 have CDPX1 in varying severity. This condition is not linked to a specific ethnicity. The mutation that leads to a deficiency in arylsulfatase E. (ARSE) occurs in the coding region of the gene. Absence of stippling, deposits of calcium, of bones and cartilage, shown on x-ray, does not rule out chondrodysplasia punctata or a normal chondrodysplasia punctata 1 (CDPX1) gene without mutation. Stippling of the bones and cartilage is rarely seen after childhood. Phalangeal abnormalities are important clinical features to look for once the stippling is no longer visible. Other, more severe, clinical features include respiratory abnormalities, hearing loss, cervical spine abnormalities, delayed cognitive development, ophthalmologic abnormalities, cardiac abnormalities, gastroesophageal reflux, and feeding difficulties. CDPX1 actually has a spectrum of severity; different mutations within the CDPX1 gene have different effects on the catalytic activity of the ARSE protein. The mutations vary between missense, nonsense, insertions, and deletions.

text: The late Devonian vertebrate transition was not the only terrestrial invasion in evolutionary history. The vertebrate transition was preceded by the plant and invertebrate terrestrial invasion. These invasions allowed for the appropriate niche development that would ultimately facilitate the vertebrate invasion. Furthermore, the late Devonian event is only significant in that it was the first land invasion by vertebrate organisms, and that it resulted in an explosion of vertebrate biodiversity due to the many different niches that these species were able to exploit. However, aquatic species have continued to develop adaptations suited to terrestrial life (and vice versa) from the late Devonian to the Holocene.

text: The late Devonian vertebrate transition was not the only terrestrial invasion in evolutionary history. The vertebrate transition was preceded by the plant and invertebrate terrestrial invasion. These invasions allowed for the appropriate niche development that would ultimately facilitate the vertebrate invasion. Furthermore, the late Devonian event is only significant in that it was the first land invasion by vertebrate organisms, and that it resulted in an explosion of vertebrate biodiversity due to the many different niches that these species were able to exploit. However, aquatic species have continued to develop adaptations suited to terrestrial life (and vice versa) from the late Devonian to the

text: Holocene

text: Likely being among the first amniotes in the biological sense, it would have laid amniotic egg not dependent on being laid in water to survive, possibly hiding them in damp vegetation or hollowed out tree stumps. This has been inferred from the fact that Casineria was found in rocks showing a rather dry environment. In the early Carboniferous period before the appearance of Casineria, vertebrates were primarily aquatic, only spending part of their time on land. Casineria and its relatives were the first vertebrates to live and reproduce on land.

text: Likely being among the first

text: amniote

text: s in the biological sense, it would have laid amniotic

text: egg

text: not dependent on being laid in water to survive, possibly hiding them in damp vegetation or hollowed out tree stumps. This has been inferred from the fact that Casineria was found in rocks showing a rather dry environment. In the early Carboniferous period before the appearance of Casineria, vertebrates were primarily aquatic, only spending part of their time on land. Casineria and its relatives were the first vertebrates to live and reproduce on land.

text: Most vertebrate species possess two or three forms of gonadotropin-releasing hormone (GnRH) expressed in three distinct brain regions. Although the function of the hypothalamic form (GnRH1; common to many vertebrates), in controlling the reproductive axis has been defined, the functions of the other two isoforms (GnRH2 and GnRH3) remain largely unknown. The presence and conservation of GnRH2 across vertebrate species indicate important biological roles, but the absence of GnRH2 in rodents has greatly hampered the use of these vertebrate models and modern molecular tools to pursue its functions.

text: A typical vertebra consists of two parts: the vertebral body and the vertebral arch. The vertebral arch is posterior, meaning it faces the back of a person. Together, these enclose the vertebral foramen, which contains the spinal cord. Because the spinal cord ends in the lumbar spine, and the sacrum and coccyx are fused, they do not contain a central foramen. The vertebral arch is formed by a pair of pedicles and a pair of laminae, and supports seven processes, four articular, two transverse, and one spinous, the latter also being known as the neural spine. Two transverse processes and one spinous process are posterior to (behind) the vertebral body. The spinous process comes out the back, one transverse process comes out the left, and one on the right. The spinous processes of the cervical and lumbar regions can be felt through the skin.

text: A typical vertebra consists of two parts: the

text: vertebral body

text: and the

text: vertebral arch

text: . The vertebral arch is

text: posterior

text: , meaning it faces the back of a person. Together, these enclose the

text: vertebral foramen

text: , which contains the

text: spinal cord

text: . Because the spinal cord ends in the lumbar spine, and the sacrum and coccyx are fused, they do not contain a central foramen. The vertebral arch is formed by a pair of

text: pedicles

text: and a pair of

text: laminae

text: , and supports seven

text: processes

text: , four articular, two transverse, and one spinous, the latter also being known as the neural spine. Two

text: transverse process

text: es and one

text: spinous process

text: are posterior to (behind) the vertebral body. The spinous process comes out the back, one transverse process comes out the left, and one on the right. The spinous processes of the cervical and lumbar regions can be felt through the skin.

text: The number of described vertebrate species are split evenly between tetrapods and fish. The following table lists the number of described extant species for each vertebrate class as estimated in the IUCN Red List of Threatened Species, 2014.3.

text: The number of described vertebrate species are split evenly between

text: tetrapod

text: s and

text: fish

text: . The following table lists the number of described

text: extant

text: species for each vertebrate

text: class

text: as estimated in the

text: IUCN Red List of Threatened Species

text: , 2014.3.

text: Fish eyes are broadly similar to those of other vertebrates – notably the tetrapods (amphibians, reptiles, birds and mammals – all of which evolved from a fish ancestor). Light enters the eye at the cornea, passing through the pupil to reach the lens. Most fish species seem to have a fixed pupil size, but elasmobranches (like sharks and rays) have a muscular iris which allows pupil diameter to be adjusted. Pupil shape varies, and may be e.g. circular or slit-like.

text: Fish eyes are broadly similar to those of other vertebrates – notably the

text: tetrapod

text: s (amphibians, reptiles, birds and mammals – all of which evolved from a fish ancestor). Light enters the eye at the

text: cornea

text: , passing through the

text: pupil

text: to reach the

text: lens

text: . Most fish species seem to have a fixed pupil size, but

text: elasmobranch

text: es (like sharks and rays) have a muscular

text: iris

text: which allows pupil diameter to be adjusted. Pupil shape varies, and may be e.g. circular or slit-like.

text: The true gill slits in embryonic fish develop into fish gills. However, the slits in tetrapods do not, so a more general name for the vertebral structures is pharyngeal slits. Gill slits likely originated from pharyngeal slits in tunicates that were used for filter-feeding. The term "gill slits" has also been used to refer to the folds of skin in the pharyngeal region in embryos. It is now accepted that it is the vertebrate pharyngeal pouches and not the neck slits that are homologous to the pharyngeal slits of invertebrate chordates.

text: The true gill slits in embryonic fish develop into

text: fish gill

text: s. However, the slits in

text: tetrapod

text: s do not, so a more general name for the vertebral structures is

text: pharyngeal slit

text: s. Gill slits likely originated from pharyngeal slits in

text: tunicate

text: s that were used for

text: filter-feeding

text: . The term "gill slits" has also been used to refer to the folds of skin in the pharyngeal region in embryos. It is now accepted that it is the vertebrate pharyngeal pouches and not the neck slits that are homologous to the pharyngeal slits of invertebrate

text: chordates

text: Prior to Hayflick's discovery, it was believed that vertebrate cells had an unlimited potential to replicate. Alexis Carrel, a Nobel prize-winning surgeon, had stated "that all cells explanted in culture are immortal, and that the lack of continuous cell replication was due to ignorance on how best to cultivate the cells". He supported this hypothesis by claiming to have cultivated fibroblasts from chicken hearts and to have kept the culture growing for 34 years. This indicated that cells of vertebrates could continue to divide indefinitely in a culture. However, other scientists have been unable to repeat Carrel's result.

text: Prior to Hayflick's discovery, it was believed that

text: vertebrate

text: cells had an unlimited potential to replicate.

text: Alexis Carrel

text: , a

text: Nobel prize

text: -winning surgeon, had stated "that all cells explanted in

text: culture

text: are immortal, and that the lack of continuous cell replication was due to ignorance on how best to cultivate the cells". He supported this hypothesis by claiming to have cultivated

text: fibroblasts

text: from

text: chicken

text: hearts and to have kept the culture growing for 34 years. This indicated that cells of

text: vertebrate

text: s could continue to divide indefinitely in a culture. However, other scientists have been unable to repeat Carrel's result.

text: Endothermy demands frequent respiration, which can result in water loss. In living birds and mammals, water loss is limited by pulling moisture out of exhaled air with mucous-covered respiratory turbinates, tissue-covered bony sheets in the nasal cavity. Several dinosaurs have olfactory turbinates, used for smell, but none have yet been identified with respiratory turbinates.

text: Between 35 and 50% of all women over 50 had at least one vertebral fracture. In the United States, 700,000 vertebral fractures occur annually, but only about a third are recognized. In a series of 9704 women aged 68.8 on average studied for 15 years, 324 had already suffered a vertebral fracture at entry into the study and 18.2% developed a vertebral fracture, but that risk rose to 41.4% in women who had a previous vertebral fracture.

text: Between 35 and 50% of all women over 50 had at least one

text: vertebral fracture

text: . In the United States, 700,000 vertebral fractures occur annually, but only about a third are recognized. In a series of 9704 women aged 68.8 on average studied for 15 years, 324 had already suffered a vertebral fracture at entry into the study and 18.2% developed a vertebral fracture, but that risk rose to 41.4% in women who had a previous vertebral fracture.

text: Ossicles are small calcareous elements embedded in the dermis of the body wall of echinoderms. They form part of the endoskeleton and provide rigidity and protection. They are found in different forms and arrangements in sea urchins, starfish, brittle stars, sea cucumbers, and crinoids. The ossicles and spines (which are specialised sharp ossicles) are the only parts of the animal likely to be fossilized after an echinoderm dies.

text: Ossicles are small

text: calcareous

text: elements embedded in the

text: dermis

text: of the body wall of

text: echinoderm

text: s. They form part of the

text: endoskeleton

text: and provide rigidity and protection. They are found in different forms and arrangements in

text: sea urchin

text: s,

text: starfish

text: brittle star

text: s,

text: sea cucumber

text: s, and

text: crinoid

text: s. The ossicles and spines (which are specialised sharp ossicles) are the only parts of the animal likely to be fossilized after an echinoderm dies.

text: Thermoregulation in both ectotherms and endotherms is controlled mainly by the preoptic area of the anterior hypothalamus. Such homeostatic control is separate from the sensation of temperature.

text: Thermoregulation in both ectotherms and endotherms is controlled mainly by the

text: preoptic area

text: of the

text: anterior hypothalamus

text: . Such

text: homeostatic

text: control is separate from the

text: sensation of temperature

text: The blood eagle is a ritualized method of execution, detailed in late skaldic poetry. According to the two instances mentioned in the Sagas, the victim (always a member of a royal family) was placed prone, the ribs severed from the vertebral column with a sharp implement and the lungs pulled through the opening to create a pair of “wings”. There is a continuing debate about whether the ritual was a literary invention, a mistranslation of the original texts or an actual historical practice.

text: The blood eagle is a ritualized method of

text: execution

text: , detailed in late

text: skaldic poetry

text: . According to the two instances mentioned in the

text: Saga

text: s, the victim (always a member of a

text: royal family

text: ) was placed prone, the ribs severed from the vertebral column with a sharp implement and the lungs pulled through the opening to create a pair of “wings”. There is a continuing debate about whether the ritual was a literary invention, a mistranslation of the original texts or an actual historical practice.

text: The coelacanths which live near Sodwana Bay, South Africa, rest in caves at depths of 90 to 150 m during daylight hours, but disperse and swim to depths as shallow as 55 m when hunting at night. The depth is not as important as their need for very dim light and, more importantly, for water which has a temperature of 14 to 22 °C.  They will rise or sink to find these conditions. The amount of oxygen their blood can absorb from the water through the gills is dependent on water temperature.  Scientific research suggests the coelacanth must stay in cold, well-oxygenated water or else its blood cannot absorb enough oxygen. The fish seems to be very well adapted to its environment, which is seen as one of the reasons why it has the slowest evolving genome of all known vertebrates.

text: The coelacanths which live near

text: Sodwana Bay

text: South Africa

text: , rest in caves at depths of 90 to 150 m during daylight hours, but disperse and swim to depths as shallow as 55 m when hunting at night. The depth is not as important as their need for very dim light and, more importantly, for water which has a temperature of 14 to 22 °C.  They will rise or sink to find these conditions. The amount of oxygen their blood can absorb from the water through the gills is dependent on water temperature.  Scientific research suggests the coelacanth must stay in cold, well-oxygenated water or else its blood cannot absorb enough oxygen. The fish seems to be very well adapted to its environment, which is seen as one of the reasons why it has the slowest evolving genome of all known vertebrates.

text: Some vertebrates also reproduce via spermatophores. Males of most salamander and newt species create spermatophores, which the females may choose to take up or not, depending on the success of the male's mating display.

text: Some vertebrates also reproduce via spermatophores. Males of most

text: salamander

text: and

text: newt

text: species create spermatophores, which the females may choose to take up or not, depending on the success of the male's mating display.

text: Paraxial mesoderm surrounding the notochord at the sides will develop into the somites (future muscles, bones, and contributes to the formation of limbs of the vertebrate ).

text: Paraxial mesoderm

text: surrounding the notochord at the sides will develop into the

text: somites

text: (future muscles, bones, and contributes to the formation of limbs of the

text: vertebrate

text: Specific to the cervical vertebra is the transverse foramen (also known as foramen transversarium). This is an opening on each of the transverse processes which gives passage to the vertebral artery and vein and a sympathetic nerve plexus. On the cervical vertebrae other than the atlas, the anterior and posterior tubercles are on either side of the transverse foramen on each transverse process. The anterior tubercle on the sixth cervical vertebra is called the carotid tubercle because it separates the carotid artery from the vertebral artery.

text: Specific to the cervical vertebra is the transverse foramen (also known as foramen transversarium). This is an opening on each of the transverse processes which gives passage to the

text: vertebral artery

text: and

text: vein

text: and a

text: sympathetic nerve plexus

text: . On the cervical vertebrae other than the atlas, the anterior and posterior tubercles are on either side of the transverse foramen on each transverse process. The anterior tubercle on the sixth cervical vertebra is called the carotid tubercle because it separates the

text: carotid artery

text: from the

text: vertebral artery

text: There exists evidence for vertebrate speciation despite limitations imposed by the fossil record. Studies have been conducted documenting similar patterns seen in marine invertebrates. For example, extensive research documenting rates of morphological change, evolutionary trends, and speciation patterns in small mammals has significantly contributed to the scientific literature; once more, demonstrating that evolution (and speciation) occurred in the past and lends support common ancestry.

text: Like all Plasmodium species P. booliati has both vertebrate and insect hosts. The vertebrate hosts for this parasite are mammals.

text: Like all Plasmodium species P. booliati has both

text: vertebrate

text: and

text: insect

text: mammal

text: s.

text: Molecular phylogeny research by Kraus et al. (2010) based on a part of "intron 9" of the gamma-glutamyl carboxylase gene has shown that feeding on fish has evolved at least twice independently in the group.

text: Molecular phylogeny

text: research by Kraus et al. (2010) based on a part of "

text: intron

text: 9" of the

text: gamma-glutamyl carboxylase

text: gene has shown that feeding on fish has evolved at least twice independently in the group.

text: There are also a number of fish with elongated bodies that have no or reduced appendage-like fins, for example eels and swamp eels. While hagfish and lamprey also do not have appendage-like fins, they may not have lost them, but simply retained the form that vertebrates had before they evolved limbs.

text: There are also a number of fish with elongated bodies that have no or reduced appendage-like fins, for example

text: eel

text: s and

text: swamp eel

text: s. While

text: hagfish

text: and

text: lamprey

text: also do not have appendage-like fins, they may not have lost them, but simply retained the form that vertebrates had before they evolved limbs.

text: The Ezh2 gene (enhancer of zeste homolog 2) is a component of polycomb repressive complex 2 (PRC2). This histone methyltransferase performs its biological activity by catalyzing the trimethylation of histone 3 lysine 27 (H3K27me3). The biological function of this gene allows for it to transcriptionally repress the target, Hox,  inhibitor genes of osteochodrogenesis. Ezh2 is crucial for epigenetic regulation of specific patterning during osteochondrogenesis, or bone and cartilage development, of the craniofacial skeletal elements.  By repressing inhibitors, Ezh2 promotes bone and cartilage formation in facial skeletal features arising from the neural crest.  Above average Ezh2 expression has become a biological marker for the most aggressive form for breast cancer known as Inflammatory Breast Cancer (IBC). But in 2013, a study performed by Zhaomei Mu and his associates concluded that the knockdown gene for Ezh2 inhibited both the migration and invasion of IBC cells. Also in vivo, its knockdown gene suppressed tumor growth, most likely by the presence of fewer blood vessels, or reduced angiogenesis, in the Ezh2 knockdown tumor versus Ezh2 tumors.

text: The Ezh2 gene (enhancer of zeste homolog 2) is a component of

text: polycomb repressive complex 2

text: (PRC2). This histone methyltransferase performs its biological activity by catalyzing the trimethylation of histone 3 lysine 27 (H3K27me3). The biological function of this gene allows for it to transcriptionally repress the target, Hox,  inhibitor genes of osteochodrogenesis. Ezh2 is crucial for epigenetic regulation of specific patterning during osteochondrogenesis, or bone and cartilage development, of the craniofacial skeletal elements.  By repressing inhibitors, Ezh2 promotes bone and cartilage formation in facial skeletal features arising from the neural crest.  Above average Ezh2 expression has become a biological marker for the most aggressive form for

text: breast cancer

text: known as

text: Inflammatory Breast Cancer

text: (IBC). But in 2013, a study performed by Zhaomei Mu and his associates concluded that the knockdown gene for Ezh2 inhibited both the migration and invasion of IBC cells. Also in vivo, its knockdown gene suppressed tumor growth, most likely by the presence of fewer blood vessels, or reduced angiogenesis, in the Ezh2 knockdown tumor versus Ezh2 tumors.

text: Parker's distinction was to carry out a careful study of the process in a much wider variety of vertebrates; his ironic comment on the "anatomical suffering caused to fish from their being dragged into harmony with that mischievous piece of work, the vertebrate archetype" shows, from such a gentle man, a surprising vigour in debate. "It is high time for us to have ceased from transcendentalism: of what use is it?" he asked.

text: MTE is based on an interpretation of the relationships between body size, body temperature, and metabolic rate across all organisms.  Small-bodied organisms tend to have higher mass-specific metabolic rates than larger-bodied organisms.  Furthermore, organisms that operate at warm temperatures through endothermy or by living in warm environments tend towards higher metabolic rates than organisms that operate at colder temperatures.  This pattern is consistent from the unicellular level up to the level of the largest animals and plants on the planet.

text: MTE is based on an interpretation of the relationships between body size, body temperature, and

text: metabolic rate

text: across all organisms.  Small-bodied organisms tend to have higher mass-specific metabolic rates than larger-bodied organisms.  Furthermore, organisms that operate at warm temperatures through

text: endothermy

text: or by living in warm environments tend towards higher metabolic rates than organisms that operate at colder temperatures.  This pattern is consistent from the unicellular level up to the level of the largest animals and plants on the planet.

text: Sanjuansaurus was named and described in 2010 by Oscar Alcober and Ricardo Martinez. The type species was named S. gordilloi after Raul Gordillo, the head fossil preparator and artist of the San Juan Museum. It is known from and based on an associated and partially articulated partial skeleton (PVSJ 605) consisting of a jaw fragment, most of the vertebral column from the axis to the anterior tail, the shoulder blades, an ulna, part of the pelvis, most of the long bones of the legs, and a few other bones.

text: Sanjuansaurus was named and described in

text: by Oscar Alcober and Ricardo Martinez. The

text: type species

text: was named S. gordilloi after Raul Gordillo, the head fossil preparator and artist of the San Juan Museum. It is known from and

text: based on

text: an associated and partially articulated partial skeleton (

text: PVSJ

text: 605) consisting of a

text: jaw

text: fragment, most of the

text: vertebral column

text: from the

text: axis

text: to the

text: anterior

text: tail, the

text: shoulder blades

text: , an

text: ulna

text: , part of the

text: pelvis

text: , most of the

text: long bone

text: s of the legs, and a few other bones.

text: As in the picture on the right where both air and barium are used together (hence the term "double-contrast" barium enema) air can be used as a contrast material because it is less radio-opaque than the tissues it is defining. In the picture it highlights the interior of the colon. An example of a technique using purely air for the contrast medium is an air arthrogram where the injection of air into a joint cavity allows the cartilage covering the ends of the bones to be visualized.

text: As in the picture on the right where both air and barium are used together (hence the term "double-contrast" barium enema) air can be used as a contrast material because it is less radio-opaque than the tissues it is defining. In the picture it highlights the interior of the colon. An example of a technique using purely air for the contrast medium is an

text: air arthrogram

text: where the injection of air into a joint cavity allows the cartilage covering the ends of the bones to be visualized.

text: If the theory that language could have evolved as a single adaptation is accepted, the question becomes which of its many functions has been the basis of adaptation, several evolutionary hypotheses have been posited: that it evolved for the purpose of social grooming, that it evolved to as a way to show mating potential or that it evolved to form social contracts. Evolutionary psychologists recognize that these theories are all speculative and that much more evidence is required to understand how language might have been selectively adapted.

text: Vertebrates typically have four cone opsins (LWS, SWS1, SWS2, and Rh2) inherited from the first vertebrate (and thus predating the first vertebrate), as well as the rod opsin, rhodopsin (Rh1), which emerged after the first vertebrate but before the first Gnathostome (jawed vertebrate). These five opsins emerged through a series of gene duplications beginning with LWS and ending with Rh1. Each one has since evolved into numerous variants and thus constitutes an opsin family or subtype.

text: Vertebrates typically have four cone opsins (LWS, SWS1, SWS2, and Rh2) inherited from the first vertebrate (and thus predating the first vertebrate), as well as the rod opsin, rhodopsin (Rh1), which emerged after the first vertebrate but before the first

text: Gnathostome

text: (jawed vertebrate). These five opsins emerged through a series of gene duplications beginning with LWS and ending with Rh1. Each one has since evolved into numerous variants and thus constitutes an opsin family or subtype.

text: Lampris guttatus are able to maintain their eyes and brain at 2 °C warmer than their bodies, a phenomenon called cranial endothermy and one they share with sharks in the Lamnidae family, billfishes and some tunas. This may allow their eyes and brains to continue functioning during deep dives into water below 4 °C.

text: Lampris guttatus are able to maintain their eyes and brain at 2 °C warmer than their bodies, a phenomenon called cranial endothermy and one they share with sharks in the

text: Lamnidae

text: family,

text: billfish

text: es and some tunas. This may allow their eyes and brains to continue functioning during deep dives into water below 4 °C.

text: The Haemosporidia have more complex lifecycles that alternate between an arthropod and a vertebrate host. The trophozoite parasitises erythrocytes or other tissues in the vertebrate host. Microgametes and macrogametes are always found in the blood. The gametes are taken up by the insect vector during a blood meal. The microgametes migrate within the gut of the insect vector and fuse with the macrogametes. The fertilized macrogamete now becomes an ookinete, which penetrates the body of the vector. The ookinete then transforms into an oocyst and divides initially by meiosis and then by mitosis (haplontic lifecycle) to give rise to the sporozoites. The sporozoites escape from the oocyst and migrate within the body of the vector to the salivary glands where they are injected into the new vertebrate host when the insect vector feeds again.

text: The Haemosporidia have more complex lifecycles that alternate between an arthropod and a vertebrate host. The trophozoite parasitises

text: erythrocyte

text: s or other tissues in the vertebrate host. Microgametes and macrogametes are always found in the blood. The gametes are taken up by the insect vector during a blood meal. The microgametes migrate within the gut of the insect vector and fuse with the macrogametes. The fertilized macrogamete now becomes an

text: ookinete

text: , which penetrates the body of the vector. The ookinete then transforms into an oocyst and divides initially by meiosis and then by mitosis (haplontic lifecycle) to give rise to the

text: sporozoite

text: s. The sporozoites escape from the oocyst and migrate within the body of the vector to the salivary glands where they are injected into the new vertebrate host when the insect vector feeds again.

text: The vertebral column consists of 5 parts. The most cranial (uppermost) part is made up by the cervical vertebrae (7), followed by thoracic (12), lumbar (5), sacral (4–5) and coccygeal vertebrae (3–4).

text: The vertebral column consists of 5 parts. The most cranial (uppermost) part is made up by the

text: cervical vertebrae

text: (7), followed by thoracic (12), lumbar (5), sacral (4–5) and coccygeal vertebrae (3–4).

text: The Vertebral Artery Test or Wallenberg Test is a physical exam for vertebral artery insufficiency.

text: The Vertebral Artery Test or Wallenberg Test is a physical exam for

text: vertebral artery

text: insufficiency.

text: The first jawed vertebrates appeared in the latest Ordovician and became common in the Devonian, often known as the "Age of Fishes". The two groups of bony fishes, the actinopterygii and sarcopterygii, evolved and became common. The Devonian also saw the demise of virtually all jawless fishes, save for lampreys and hagfish, as well as the Placodermi, a group of armoured fish that dominated the entirety of that period since the late Silurian. The Devonian also saw the rise of the first labyrinthodonts, which was a transitional form between fishes and amphibians.

text: The first

text: jawed vertebrates

text: appeared in the latest

text: Ordovician

text: and became common in the

text: Devonian

text: bony fishes

text: , the

text: actinopterygii

text: and

text: sarcopterygii

text: Placodermi

text: , a group of armoured fish that dominated the entirety of that period since the late

text: Silurian

text: labyrinthodonts

text: , which was a transitional form between fishes and

text: amphibians

text: The introduction takes the story in the prologue two weeks forward to 8 October, the day when the bank recapitalisation plan was announced. Brown describes how the crises evolved to become much wider than a banking crises - it became what he calls the first crises of globalisation, which if not overcome will threaten a decade or more of low growth, with millions left jobless and millions more in poverty.  Brown recalls that in the last years of the 20th century, Europe and America had between them a majority share of the world's production, exports and investment. While after 2000 Europe and American had a minority share in all those areas, while still retaining a large majority of the world's consumption, financed by borrowing from the rest of the world. Brown states that this recently developed situation has become unsustainable. He says it's essential for emerging economic giants like China to further boost their consumption if global growth is to be optimised and the crises is to be fully overcome.  The introduction also discusses the need for morality to inform the conduct of market participants.

text: A study published by Roger Seymour in 2013 added more support to the idea that dinosaurs were endothermic. After studying saltwater crocodiles, Seymour found that even if their large sizes could provide stable and high body temperatures, the crocodiles' ectothermic metabolisms provided less endurance and only 14% of the muscle power of a similar sized mammal. Seymour reasoned that dinosaurs would have needed to be endothermic since they would have needed powerful muscles and endurance to compete with and dominate mammals throughout the Mesozoic era.

text: The sacral nerves are the five pairs of spinal nerves which exit the sacrum at the lower end of the vertebral column. The roots of these nerves begin inside the vertebral column at the level of the L1 vertebra, where the cauda equina begins, and then descend into the sacrum.

text: The sacral nerves are the five pairs of spinal nerves which exit the

text: sacrum

text: at the lower end of the

text: vertebral column

text: . The roots of these nerves begin inside the vertebral column at the level of the

text: L1 vertebra

text: , where the

text: cauda equina

text: begins, and then descend into the sacrum.

text: Histological analysis of cross-sections of the ribs indicate that they grew in three different phases as an individual developed. As is the case in most land vertebrates, the first phase involves the growth of a rib primordium that ossifies (ossifies) into a rib bone. The second phase, which deviates from most other land vertebrates, is the development of a shelf of bone above the main shaft of the rib to form the T-shape. The third and final phase is the widening of the lower ridge into a teardrop-like shape, reinforcing the rib. While the third phase is unique to Eunotosaurus, the second phase is also seen in modern turtles. In turtles, the shelf of bone that forms from the rib shaft becomes a plate of the shell or carapace. In each rib of Eunotosaurus, the posterior surface of the lower ridge has Sharpey's fibers embedded in it. Sharpey's fibers help anchor muscles to bone. Most amniotes have Sharpey's fibers on the posterior and anterior edges of the ribs because the ribs are connected to each other by intercostal muscles, which are muscles that assist in breathing. The lack of Sharpey's fibers on the anterior side of the ribs of Eunotosaurus suggests that it lacked functional intercostal muscles. Turtles also lack intercostal muscles and instead have muscles that connect to the undersides of the ribs for the purpose of locomotion. If Eunotosaurus is close to the ancestry of turtles, it may have had similar sets of muscles.

text: Histological

text: analysis of cross-sections of the ribs indicate that they grew in three different phases as an individual developed. As is the case in most land vertebrates, the first phase involves the growth of a rib

text: primordium

text: that

text: ossifies

text: (ossifies) into a rib bone. The second phase, which deviates from most other land vertebrates, is the development of a shelf of bone above the main shaft of the rib to form the T-shape. The third and final phase is the widening of the lower ridge into a teardrop-like shape, reinforcing the rib. While the third phase is unique to Eunotosaurus, the second phase is also seen in modern turtles. In turtles, the shelf of bone that forms from the rib shaft becomes a plate of the shell or

text: carapace

text: . In each rib of Eunotosaurus, the posterior surface of the lower ridge has

text: Sharpey's fibers

text: embedded in it. Sharpey's fibers help anchor muscles to bone. Most

text: amniote

text: s have Sharpey's fibers on the posterior and anterior edges of the ribs because the ribs are connected to each other by

text: intercostal muscle

text: s, which are muscles that assist in breathing. The lack of Sharpey's fibers on the anterior side of the ribs of Eunotosaurus suggests that it lacked functional intercostal muscles. Turtles also lack intercostal muscles and instead have muscles that connect to the undersides of the ribs for the purpose of locomotion. If Eunotosaurus is close to the ancestry of turtles, it may have had similar sets of muscles.

text: A digit is one of several most distal parts of a limb, such as fingers or toes, present in many vertebrates.

text: A digit is one of several most distal parts of a

text: limb

text: , such as

text: finger

text: s or

text: toe

text: s, present in many

text: vertebrate

text: s.

text: The fauna of the Wuyi Mountains is renowned for its high diversity, which includes many rare and unusual species. In total, approximately 5,000 animal species have been reported for the area. 475 of these species are vertebrates and 4,635 insects. The number of vertebrate species is divided as follows:

text: The fauna of the Wuyi Mountains is renowned for its high diversity, which includes many rare and unusual species. In total, approximately 5,000 animal species have been reported for the area. 475 of these species are

text: vertebrate

text: s and 4,635

text: insect

text: s. The number of vertebrate species is divided as follows:

text: Arabidopsis thaliana is currently the most popular model plant. Its small stature and short generation time facilitates rapid genetic studies, and many phenotypic and biochemical mutants have been mapped. Arabidopsis was the first plant to have its genome sequenced. Among vertebrates, guinea pigs (Cavia porcellus) were used by Robert Koch and other early bacteriologists as a host for bacterial infections, becoming a byword for "laboratory animal," but are less commonly used today. The classic model vertebrate is currently the mouse (Mus musculus). Many inbred strains exist, as well as lines selected for particular traits, often of medical interest, e.g. body size, obesity, muscularity, and voluntary wheel-running behavior.

text: Arabidopsis thaliana

text: is currently the most popular model plant. Its small stature and short generation time facilitates rapid genetic studies, and many phenotypic and biochemical mutants have been mapped. Arabidopsis was the first plant to have its

text: genome

text: sequenced

text: . Among

text: vertebrate

text: s,

text: guinea pig

text: s (Cavia porcellus) were used by

text: Robert Koch

text: and other early bacteriologists as a host for bacterial infections, becoming a byword for "laboratory animal," but are less commonly used today. The classic model vertebrate is currently the mouse (

text: Mus musculus

text: ). Many inbred strains exist, as well as lines selected for particular traits, often of medical interest, e.g. body size, obesity, muscularity, and voluntary

text: wheel-running

text: behavior.

text: In some vertebrates, exposure to light can set off a chain reaction of enzymatic events within the pineal gland that regulate circadian rhythms. Some early vertebrate fossil skulls have a pineal foramen (opening). This correlates with the physiology of the modern "living fossils," the lampreys and the tuatara, and some other vertebrates that have a parietal eye, which, in some of them, is photosensitive. The parietal eye represents evolution's earlier approach to photoreception. The structures of the pineal eye in the tuatara are analogous to the cornea, lens, and retina, though the latter resembles that of an octopus rather than a vertebrate retina. The asymmetrical whole consists of the "eye" to the left and the pineal sac to the right. "In animals that have lost the parietal eye, including mammals, the pineal sac is retained and condensed into the form of the pineal gland."

text: In some vertebrates, exposure to light can set off a chain reaction of enzymatic events within the pineal gland that regulate

text: circadian rhythm

text: s. Some early vertebrate fossil skulls have a pineal

text: foramen

text: (opening). This correlates with the physiology of the modern "

text: living fossil

text: s," the

text: lamprey

text: s and the

text: tuatara

text: , and some other vertebrates that have a

text: parietal eye

text: , which, in some of them, is photosensitive. The parietal eye represents evolution's earlier approach to photoreception. The structures of the pineal eye in the tuatara are analogous to the cornea, lens, and retina, though the latter resembles that of an octopus rather than a vertebrate retina. The asymmetrical whole consists of the "eye" to the left and the pineal sac to the right. "In animals that have lost the parietal eye, including mammals, the pineal sac is retained and condensed into the form of the pineal gland."

text: Vertebrates are known from both body fossils and trace fossils. Vertebrate known from body fossils include (the following after Lucas et al. [2005], except where noted): hybodont sharks, indeterminate bony fish, lungfish, salamanders, the frog Prosalirus, the caecilian Eocaecilia, the turtle Kayentachelys, a sphenodontian reptile, lizards, several early crocodylomorphs including Calsoyasuchus, Eopneumatosuchus, Kayentasuchus, and Protosuchus), the pterosaur Rhamphinion, several theropods including Dilophosaurus, Kayentavenator Coelophysis kayentakatae, and the "Shake N Bake" theropod, the basal sauropodomorph Sarahsaurus, a heterodontosaurid, armored dinosaurs Scelidosaurus and Scutellosaurus, the tritylodontids synapsids Dinnebiton, Kayentatherium, and Oligokyphus, morganucodontids, possible early true mammal Dinnetherium, and a haramyid mammal. The majority of these finds come from the vicinity of Gold Spring, Arizona. Vertebrate trace fossils include coprolites and the tracks of therapsids, lizard-like animals, and several types of dinosaur.

text: Vertebrates are known from both body fossils and trace fossils. Vertebrate known from body fossils include (the following after Lucas et al. [2005], except where noted):

text: hybodont

text: sharks, indeterminate

text: bony fish

text: lungfish

text: , salamanders, the frog

text: Prosalirus

text: , the

text: caecilia

text: n

text: Eocaecilia

text: , the turtle

text: Kayentachelys

text: , a

text: sphenodontia

text: n reptile, lizards, several early

text: crocodylomorphs

text: including

text: Calsoyasuchus

text: Eopneumatosuchus

text: Kayentasuchus

text: , and

text: Protosuchus

text: ), the

text: pterosaur

text: Rhamphinion

text: , several theropods including Dilophosaurus,

text: Kayentavenator

text: Coelophysis kayentakatae

text: , and the "Shake N Bake" theropod, the

text: basal

text: sauropodomorph

text: Sarahsaurus

text: , a

text: heterodontosaurid

text: , armored dinosaurs

text: Scelidosaurus

text: and

text: Scutellosaurus

text: , the

text: tritylodontids

text: synapsids

text: Dinnebiton,

text: Kayentatherium

text: , and

text: Oligokyphus

text: morganucodontids

text: , possible early true mammal Dinnetherium, and a

text: haramyid

text: mammal. The majority of these finds come from the vicinity of Gold Spring, Arizona. Vertebrate trace fossils include

text: coprolite

text: s and the tracks of

text: therapsid

text: s, lizard-like animals, and several types of dinosaur.

text: In humans, the chondrocranium begins forming at 28 days from mesenchymal condensations and is fully formed between week 7 and 9 of fetal development. While the majority of the chondrocranium is succeeded by the bony skull in most higher vertebrates, some components do persist into adulthood. In cartilaginous fishes (e.g. sharks and rays) and agnathans (e.g. lampreys and hagfish), the chondrocranium persists throughout life. Embryologically, the chondrocranium represents the basal cranial structure, and lays the base for the formation of the endocranium in higher vertebrates.

text: In

text: human

text: s, the chondrocranium begins forming at 28 days from

text: mesenchymal

text: condensations and is fully formed between week 7 and 9 of fetal development. While the majority of the chondrocranium is succeeded by the bony skull in most higher

text: vertebrates

text: , some components do persist into adulthood. In

text: cartilaginous fishes

text: (e.g.

text: shark

text: s and

text: rays

text: ) and

text: agnatha

text: ns (e.g.

text: lamprey

text: s and

text: hagfish

text: ), the chondrocranium persists throughout life.

text: Embryologically

text: , the chondrocranium represents the basal cranial structure, and lays the base for the formation of the

text: endocranium

text: in

text: higher vertebrates

text: In many respects fish anatomy is different from humans and  mammals, yet it shares the same basic vertebrate body plan from which all vertebrates have evolved: a notochord, rudimentary vertebrae, and a well-defined head and tail.

text: In many respects fish anatomy is different from humans and  mammals, yet it shares the same basic vertebrate

text: body plan

text: from which all vertebrates have evolved: a

text: notochord

text: , rudimentary

text: vertebrae

text: , and a well-defined

text: head

text: and

text: tail

text: Like all Plasmodium species P. tumbayaensis has both vertebrate and insect hosts. The vertebrate hosts for this parasite are birds.

text: Like all Plasmodium species P. tumbayaensis has both

text: vertebrate

text: and

text: insect

text: birds

text: In May 2015, L. guttatus was shown to maintain its entire body core above ambient temperature, becoming the first known fish with this trait ('whole-body endothermy').  It can consistently keep its body core approximately  warmer than its environment.

text: In May 2015, L. guttatus was shown to maintain its entire body core

text: above ambient temperature

text: , becoming the first known fish with this trait ('whole-body

text: endotherm

text: y').  It can consistently keep its body core approximately  warmer than its environment.

text: Neural crest cells are a temporary group of cells unique to vertebrates that arise from the embryonic ectoderm cell layer, and in turn give rise to a diverse cell lineage—including melanocytes, craniofacial cartilage and bone, smooth muscle, peripheral and enteric neurons and glia.

text: Neural crest cells are a temporary group of cells unique to vertebrates that arise from the embryonic

text: ectoderm

text: cell layer, and in turn give rise to a diverse cell lineage—including

text: melanocytes

text: , craniofacial cartilage and bone, smooth muscle,

text: peripheral

text: and

text: enteric neuron

text: s and

text: glia

text: In the most primitive living vertebrates, the lampreys and hagfish, there is only one nostril and olfactory pouch. Indeed, the nostril also opens into the hypophysis. This is not necessarily, however, a primitive trait, but one that may have arisen later in the evolution of these particular groups. For example, the fossil heterostracans had paired nostrils, and these were also a very early vertebrate group.

text: In the most primitive living vertebrates, the

text: lamprey

text: s and

text: hagfish

text: , there is only one nostril and olfactory pouch. Indeed, the nostril also opens into the

text: hypophysis

text: . This is not necessarily, however, a primitive trait, but one that may have arisen later in the evolution of these particular groups. For example, the fossil

text: heterostracan

text: s had paired nostrils, and these were also a very early vertebrate group.

text: True teeth are unique to vertebrates, although some invertebrates have analogous structures sometimes called "teeth". The organism with the simplest genome bearing such "teeth" is probably the worm genus Ancylostoma (Ancylostoma duodenale, Necator americanus). Molluscs have a structure called a radula which bears a ribbon of chitinous "teeth". However, these are histologically and developmentally different from vertebrate teeth, and are unlikely to be homologous. For example, vertebrate teeth develop from a neural crest mesenchyme-derived dental papilla, and the neural crest is specific to vertebrates, as are tissues such as enamel.

text: True teeth are unique to

text: vertebrates

text: , although some invertebrates have

text: analogous structures

text: sometimes called "teeth". The

text: organism

text: with the simplest

text: genome

text: bearing such "

text: teeth

text: " is probably the

text: worm

text: genus

text: Ancylostoma

text: Ancylostoma duodenale

text: Necator americanus

text: ). Molluscs have a structure called a

text: radula

text: which bears a ribbon of

text: chitin

text: ous "teeth". However, these are histologically and developmentally different from vertebrate teeth, and are unlikely to be

text: homologous

text: . For example, vertebrate teeth develop from a

text: neural crest

text: mesenchyme-derived

text: dental papilla

text: , and the neural crest is specific to vertebrates, as are tissues such as

text: enamel

text: Hard-bodied and large invertebrates are much-more commonly preserved; typically as sizeable macrofossils.  These invertebrates are more frequently preserved because their hard parts—for example, shell, armor, plates, tests, exoskeleton, jaws or teeth -- are composed of silica (silicon dioxide), calcite or aragonite (both forms of calcium carbonate), chitin (a protein often infused with tricalcium phosphate), or keratin (an even-more complex protein), rather than the vertebrate bone (hydroxyapatite) or cartilage of fishes and land-dwelling tetrapods.

text: Hard-bodied and large invertebrates are much-more commonly preserved; typically as sizeable

text: macrofossil

text: s.  These invertebrates are more frequently preserved because their hard parts—for example,

text: shell

text: armor

text: , plates,

text: test

text: s,

text: exoskeleton

text: jaw

text: s or

text: teeth

text: -- are composed of

text: silica

text: silicon dioxide

text: calcite

text: or

text: aragonite

text: (both forms of

text: calcium carbonate

text: chitin

text: (a

text: protein

text: often infused with

text: tricalcium phosphate

text: ), or

text: keratin

text: (an even-more complex

text: protein

text: ), rather than the vertebrate

text: bone

text: hydroxyapatite

text: ) or

text: cartilage

text: of

text: fish

text: es and land-dwelling

text: tetrapod

text: s.

text: In molecular biology, Adenylosuccinate synthase (or adenylosuccinate synthetase) () is an enzyme that plays an important role in purine biosynthesis, by catalysing the guanosine triphosphate (GTP)-dependent conversion of inosine monophosphate (IMP) and aspartic acid to guanosine diphosphate (GDP), phosphate and  N(6)-(1,2-dicarboxyethyl)-AMP. Adenylosuccinate synthetase has been characterised from various sources ranging from Escherichia coli (gene purA) to vertebrate tissues. In vertebrates, two isozymes are present: one involved in purine biosynthesis and the other in the purine nucleotide cycle.

text: In molecular biology, Adenylosuccinate synthase (or adenylosuccinate synthetase) () is an enzyme that plays an important role in

text: purine

text: biosynthesis, by catalysing the

text: guanosine triphosphate

text: (GTP)-dependent conversion of

text: inosine monophosphate

text: (IMP) and

text: aspartic acid

text: to

text: guanosine diphosphate

text: (GDP), phosphate and  N(6)-(1,2-dicarboxyethyl)-AMP. Adenylosuccinate synthetase has been characterised from various sources ranging from

text: Escherichia coli

text: (gene purA) to

text: vertebrate

text: tissue

text: s. In vertebrates, two

text: isozymes

text: are present: one involved in purine

text: biosynthesis

text: and the other in the purine

text: nucleotide

text: cycle.

text: The human heart is situated in the middle mediastinum, at the level of thoracic vertebrae T5-T8. A double-membraned sac called the pericardium surrounds the heart and attaches to the mediastinum. The back surface of the heart lies near the vertebral column, and the front surface sits behind to the sternum and rib cartilages. The upper part of the heart is the attachment point for several large blood vessels - the venae cavae,  aorta and pulmonary trunk. The upper part of the heart is located at the level of the third costal cartilage. The lower tip of the heart, the apex, lies to the left of the sternum (8 to 9 cm from the midsternal line) between the junction of the fourth and fifth ribs near their articulation with the costal cartilages.

text: The human heart is situated in the

text: middle mediastinum

text: , at the level of

text: thoracic vertebrae T5-T8

text: . A double-membraned sac called the

text: pericardium

text: surrounds the heart and attaches to the mediastinum. The back surface of the heart lies near the

text: vertebral column

text: , and the front surface sits behind to the

text: sternum

text: and

text: rib cartilages

text: . The upper part of the heart is the attachment point for several large blood vessels - the

text: venae cavae

text: aorta

text: and

text: pulmonary trunk

text: . The upper part of the heart is located at the level of the third costal cartilage. The lower tip of the heart, the apex, lies to the left of the sternum (8 to 9 cm from the

text: midsternal line

text: ) between the junction of the fourth and fifth ribs near their

text: articulation

text: with the costal cartilages.

text: Andersson is interested in ecology affecting fish and seeks to preserve the species of fish in the Baltic Sea.

text: Andersson is interested in ecology affecting fish and seeks to preserve the species of fish in the

text: Baltic Sea

text: Evolution of the adaptive immune system occurred in an ancestor of the jawed vertebrates. Many of the classical molecules of the adaptive immune system (e.g., immunoglobulins and T cell receptors) exist only in jawed vertebrates. However, a distinct lymphocyte-derived molecule has been discovered in primitive jawless vertebrates, such as the lamprey and hagfish. These animals possess a large array of molecules called Variable lymphocyte receptors (VLRs) that, like the antigen receptors of jawed vertebrates, are produced from only a small number (one or two) of genes. These molecules are believed to bind pathogenic antigens in a similar way to antibodies, and with the same degree of specificity.

text: Evolution of the adaptive immune system

text: occurred in an ancestor of the jawed vertebrates. Many of the classical molecules of the adaptive immune system (e.g.,

text: immunoglobulin

text: s and

text: T cell receptor

text: s) exist only in jawed vertebrates. However, a distinct

text: lymphocyte

text: -derived molecule has been discovered in primitive

text: jawless vertebrates

text: , such as the

text: lamprey

text: and

text: hagfish

text: . These animals possess a large array of molecules called

text: Variable lymphocyte receptor

text: s (VLRs) that, like the antigen receptors of jawed vertebrates, are produced from only a small number (one or two) of

text: gene

text: s. These molecules are believed to bind pathogenic

text: antigen

text: s in a similar way to antibodies, and with the same degree of specificity.

text: Coelacanths are a part of the clade Sarcopterygii, or the lobe-finned fishes. Externally, several characteristics distinguish the coelacanth from other lobe-finned fish. They possess a three-lobed caudal fin, also called a trilobate fin or a diphycercal tail. A secondary tail extending past the primary tail separates the upper and lower halves of the coelacanth. Cosmoid scales act as thick armor to protect the coelacanth's exterior. Several internal traits also aid in differentiating coelacanths from other lobe-finned fish. At the back of the skull, the coelacanth possesses a hinge, the intracranial joint, which allows it to open its mouth extremely wide. Coelacanths also retain an oil-filled notochord, a hollow, pressurized tube which is replaced by the vertebral column early in embryonic development in most other vertebrates. The coelacanth heart is shaped differently from that of most modern fish, with its chambers arranged in a straight tube. The coelacanth braincase is 98.5% filled with fat; only 1.5% of the braincase contains brain tissue. The cheeks of the coelacanths are unique because the opercular bone is very small and holds a large soft-tissue opercular flap. A spiracular chamber is present, but the spiracle is closed and never opens during development. Coelacanth also possess a unique rostral organ within the ethmoid region of the braincase. Also unique to extant coelacanths is the presence of a "fatty lung" or a fat-filled single-lobed vestigial lung, homologous to other fishes' swim bladder. The parallel development of a fatty organ for buoyancy control suggest a unique specialization for deep-water habitats. There has also been discovered small, hard but flexible plates around the vestigial lung in adult specimen, though not around the fatty organ. The plates most likely had a regulation function for the volume of the lung. Due to the size of the fatty organ, it is assumed to be responsible for the kidney's unusual relocation. The two kidneys, which are fused into one, are located ventrally within the abdominal cavity, posterior to the cloaca.

text: Coelacanths are a part of the

text: clade

text: Sarcopterygii

text: , or the lobe-finned fishes. Externally, several characteristics distinguish the coelacanth from other lobe-finned fish. They possess a three-lobed

text: caudal fin

text: , also called a trilobate fin or a diphycercal tail. A secondary tail extending past the primary tail separates the upper and lower halves of the coelacanth.

text: Cosmoid scale

text: s act as thick armor to protect the coelacanth's exterior. Several internal traits also aid in differentiating coelacanths from other lobe-finned fish. At the back of the skull, the coelacanth possesses a hinge, the

text: intracranial

text: joint, which allows it to open its mouth extremely wide. Coelacanths also retain an oil-filled

text: notochord

text: , a hollow, pressurized tube which is replaced by the

text: vertebral column

text: early in embryonic development in most other vertebrates. The coelacanth heart is shaped differently from that of most modern fish, with its chambers arranged in a straight tube. The coelacanth braincase is 98.5% filled with fat; only 1.5% of the braincase contains brain tissue. The cheeks of the coelacanths are unique because the

text: opercular

text: bone is very small and holds a large soft-tissue opercular flap. A spiracular chamber is present, but the

text: spiracle

text: is closed and never opens during development. Coelacanth also possess a unique

text: rostral organ

text: within the

text: ethmoid

text: region of the braincase. Also unique to extant coelacanths is the presence of a "fatty lung" or a fat-filled single-lobed vestigial

text: lung

text: , homologous to other fishes'

text: swim bladder

text: . The parallel development of a fatty organ for buoyancy control suggest a unique specialization for deep-water habitats. There has also been discovered small, hard but flexible plates around the vestigial lung in adult specimen, though not around the fatty organ. The plates most likely had a regulation function for the volume of the lung. Due to the size of the fatty organ, it is assumed to be responsible for the kidney's unusual relocation. The two kidneys, which are fused into one, are located ventrally within the abdominal cavity, posterior to the cloaca.

text: Though invertebrate chordates such as the lancelet have heads, there has been a question of how the vertebrate head, characterized by a bony skull clearly separated from the main body, might have evolved from the head structures of these animals. In 2014, a transient larva tissue of the lancelet was found to be virtually indistinguishable from the neural crest-derived cartilage which forms the vertebrate skull, suggesting that persistence of this tissue and expansion into the entire head space could be a viable evolutionary route to formation of the vertebrate head.

text: Though

text: invertebrate

text: chordate

text: s such as the

text: lancelet

text: have heads, there has been a question of how the vertebrate head, characterized by a bony skull clearly separated from the main body, might have evolved from the head structures of these animals. In 2014, a transient

text: larva

text: tissue of the lancelet was found to be virtually indistinguishable from the

text: neural crest

text: -derived

text: cartilage

text: which forms the vertebrate

text: skull

text: , suggesting that persistence of this tissue and expansion into the entire head space could be a viable evolutionary route to formation of the vertebrate head.

text: In modern times, Alfred Romer (1894–1973) wrote what has been termed the definitive textbook on the subject, called Vertebrate Paleontology. It shows the progression of evolution in fossil fish, and amphibians and reptiles through comparative anatomy, including a list of all the (then) known fossil vertebrate genera. Romer became the first president of the Society of Vertebrate Paleontology in 1940, alongside co-founder Howard Chiu. An updated work that largely carried on the tradition from Romer, and by many considered definitive book on the subject was written by Robert L. Carroll of McGill University, the 1988 text Vertebrate Paleontology and Evolution. Carroll was president of the Society of Vertebrate Paleontology in 1983. The Society keeps its members informed on the latest discoveries through newsletters and the Journal of Vertebrate Paleontology.

text: In modern times,

text: Alfred Romer

text: (1894–1973) wrote what has been termed the definitive textbook on the subject, called

text: Vertebrate Paleontology

text: . It shows the progression of evolution in fossil fish, and amphibians and reptiles through comparative anatomy, including a list of all the (then) known fossil vertebrate

text: genera

text: . Romer became the first president of the

text: Society of Vertebrate Paleontology

text: in 1940, alongside co-founder Howard Chiu. An updated work that largely carried on the tradition from Romer, and by many considered definitive book on the subject was written by

text: Robert L. Carroll

text: of McGill University, the 1988 text Vertebrate Paleontology and Evolution. Carroll was president of the Society of Vertebrate Paleontology in 1983. The Society keeps its members informed on the latest discoveries through newsletters and the Journal of Vertebrate Paleontology.

text: Within the vertebral column (spine) of vertebrates, including the human spine, each bone has an opening at both its top and bottom to allow nerves, arteries, veins, etc. to pass through.

text: Within the

text: vertebral column

text: (spine) of vertebrates, including the

text: human spine

text: , each bone has an opening at both its top and bottom to allow nerves, arteries, veins, etc. to pass through.

text: The genetic code is, for the most part, universal, with few exceptions: mitochondrial genetics includes some of these. For most organisms the "stop codons" are "UAA", "UAG", and "UGA". In vertebrate mitochondria "AGA" and "AGG" are also stop codons, but not "UGA", which codes for tryptophan instead. "AUA" codes for isoleucine in most organisms but for methionine in vertebrate mitochondrial mRNA.

text: The

text: genetic code

text: is, for the most part, universal, with few exceptions: mitochondrial genetics includes some of these. For most organisms the "

text: stop codon

text: s" are "UAA", "UAG", and "UGA". In vertebrate mitochondria "AGA" and "AGG" are also stop codons, but not "UGA", which codes for

text: tryptophan

text: instead. "AUA" codes for

text: isoleucine

text: in most organisms but for

text: methionine

text: in vertebrate mitochondrial mRNA.

text: Its borders are the left atrium, vertebral column, and aortic arch.

text: Its borders are the

text: left atrium

text: vertebral column

text: , and

text: aortic arch

text: Koreaceratops is notable for the tall neural spines on its caudal vertebrae, and for the structure of its astragalus. In some of the distal caudal vertebrae, the neural spines are over five times the height of the vertebral centra to which they attach.  Lee et al. noted that several other ceratopsians also had tall neural spines on their caudals.  As this trait appears in several branches of ceratopsians, Lee et al. postulated that the feature was independently evolved, perhaps as an adaptation for swimming.  Lee et al. performed a phylogenetic analysis and found Koreaceratops to be positioned between Archaeoceratops and more derived ceratopsians.

text: Koreaceratops is notable for the tall

text: neural spines

text: on its caudal vertebrae, and for the structure of its

text: astragalus

text: . In some of the

text: distal

text: caudal vertebrae, the neural spines are over five times the height of the

text: vertebral centra

text: to which they attach.  Lee et al. noted that several other ceratopsians also had tall neural spines on their caudals.  As this trait appears in several branches of ceratopsians, Lee et al. postulated that the feature was independently evolved, perhaps as an adaptation for swimming.  Lee et al. performed a

text: phylogenetic analysis

text: and found Koreaceratops to be positioned between

text: Archaeoceratops

text: and more

text: derived

text: ceratopsians.

text: Parthenogenesis is a mode of asexual reproduction in which offspring are produced by females without the genetic contribution of a male. Among vertebrates, the only examples of true parthenogenesis, in which all-female populations reproduce without the involvement of males, are found in squamate reptiles (snakes and lizards). There are about 50 species of lizard and 1 species of snake that reproduce solely through parthenogenesis (obligate parthenogenesis). It is unknown how many sexually reproducing species are also capable of parthenogenesis in the absence of males (facultative parthenogenesis), but recent research has revealed that this ability is widespread among squamates.

text: Parthenogenesis

text: is a mode of

text: asexual reproduction

text: in which offspring are produced by females without the genetic contribution of a male. Among

text: vertebrates

text: , the only examples of true parthenogenesis, in which all-female populations reproduce without the involvement of males, are found in

text: squamate

text: reptiles (

text: snakes

text: and

text: lizards

text: ). There are about 50 species of lizard and 1 species of snake that reproduce solely through parthenogenesis (obligate parthenogenesis). It is unknown how many sexually reproducing species are also capable of parthenogenesis in the absence of males (facultative parthenogenesis), but recent research has revealed that this ability is widespread among squamates.

text: The exact pathogenesis of iniencephaly is still unknown though there are proposed theories, most of which view the neural tube malformation from the primary neural anomaly standpoint.Marin-Padilla and MarinPadilla have proposed that the cause for the abnormalities has to do with a deficiency in the primary mesoderm.   P. Erdinçler, et al. suggests from their findings that the cause of the anomaly is actually a defect in the occipital bone and rachischisis of the posterior vertebral arches leading to herniation of neural tissue through the opening in the bone during gestation.

text: The exact

text: pathogenesis

text: of iniencephaly is still unknown though there are proposed theories, most of which view the neural tube malformation from the primary neural anomaly standpoint.Marin-Padilla and MarinPadilla have proposed that the cause for the abnormalities has to do with a deficiency in the primary

text: mesoderm

text: .   P. Erdinçler, et al. suggests from their findings that the cause of the anomaly is actually a defect in the

text: occipital bone

text: and

text: rachischisis

text: of the posterior vertebral arches leading to

text: herniation

text: of neural tissue through the opening in the bone during

text: gestation

text: Fish are vertebrates. All vertebrates are built along the basic chordate body plan: a stiff rod running through the length of the animal (vertebral column or notochord), with a hollow tube of nervous tissue (the spinal cord) above it and the gastrointestinal tract below. In all vertebrates, the mouth is found at, or right below, the anterior end of the animal, while the anus opens to the exterior before the end of the body. The remaining part of the body continuing aft of the anus forms a tail with vertebrae and spinal cord, but no gut.

text: Fish are

text: vertebrate

text: s. All vertebrates are built along the basic

text: chordate

text: body plan

text: : a stiff rod running through the length of the animal (

text: vertebral column

text: or

text: notochord

text: spinal cord

text: ) above it and the

text: gastrointestinal tract

text: below. In all vertebrates, the mouth is found at, or right below, the anterior end of the animal, while the

text: anus

text: opens to the exterior before the end of the body. The remaining part of the body continuing aft of the anus forms a

text: tail

text: with vertebrae and spinal cord, but no gut.

text: Herrerasaurus displays traits that are found in different groups of dinosaurs, and several traits found in non-dinosaurian archosaurs. Although it shares most of the characteristics of dinosaurs, there are a few differences, particularly in the shape of its hip and leg bones. Its pelvis is like that of saurischian dinosaurs, but it has a bony acetabulum (where the femur meets the pelvis) that was only partially open. The ilium, the main hip bone, is supported by only two sacrals, a basal trait. However, the pubis points backwards, a derived trait as seen in dromaeosaurids and birds. Additionally, the end of the pubis has a booted shape, like those in avetheropods; and the vertebral centra has an hourglass shape as found in Allosaurus.

text: Herrerasaurus displays traits that are found in different groups of dinosaurs, and several traits found in non-dinosaurian archosaurs. Although it shares most of the characteristics of dinosaurs, there are a few differences, particularly in the shape of its hip and leg bones. Its pelvis is like that of saurischian dinosaurs, but it has a bony

text: acetabulum

text: (where the

text: femur

text: meets the

text: pelvis

text: ) that was only partially open. The

text: ilium

text: , the main hip bone, is supported by only two

text: sacrals

text: , a

text: basal

text: trait. However, the

text: pubis

text: points backwards, a

text: derived

text: trait as seen in

text: dromaeosaurid

text: s and

text: bird

text: s. Additionally, the end of the pubis has a booted shape, like those in

text: avetheropods

text: ; and the

text: vertebra

text: l

text: centra

text: has an

text: hourglass

text: shape as found in

text: Allosaurus

text: Feduccia is best known for his criticisms of the hypothesis, accepted by most paleontologists, that birds originated from and are deeply nested within Theropoda, and are therefore living theropod dinosaurs.  Feduccia's first contribution relative to the origin and early evolution of birds, and their relationship with dinosaurs, was a critical review of the evidence then available for dinosaurian endothermy in 1973.  In a 1979 paper, Feduccia and Tordoff argued, against the position taken by John Ostrom, that Archaeopteryx was capable of powered flight, as indicated by the asymmetrical vanes of its primary feathers, a feature found only in flying birds.  In a paper coauthored with Storrs Olson in the same year, Feduccia noted that the robust furcula of Archaeopteryx could have served as a site of attachment for a well-developed M. pectoralis major, the principal depressor of the avian wing, responsible for powering the downstroke during avian flight.  Olson and Feduccia concluded that this provided further evidence for the flight capability of Archaeopteryx.  These initial excursions into the subject, and the argument that Archaeopteryx was clearly a bird, albeit primitive, were expanded upon in Feduccia's 1980 book, The Age of Birds.  Feduccia here criticized the theropod hypothesis for the origin of birds, but his position was largely agnostic, conceding that there was evidence in support of both a theropod ancestry of birds and an ancestry from more basal archosaurs, perhaps similar in overall morphological organization to Euparkeria.  Feduccia nevertheless suggested that on the basis of closer stratigraphic fit, ancestry from basal archosaurs rather than from coelurosaurian theropods might prove a better phylogenetic hypothesis.  He thus, essentially, agreed with the model for the origin of birds proposed by Gerhard Heilmann in his influential 1926 book The Origin of Birds.  Feduccia also criticized "ground-up" theories for the origin of avian flight, arguing on biophysical grounds that they were implausible, and noting that in other cases in which flight has developed among vertebrates it has occurred in an arboreal context.  He argued, instead, for a "trees-down" model for the origin of avian flight due to its lack of the biophysical constraints hindering "ground-up" acquisition of flight and due to the ability to call upon biologically functional stages, represented by living analogues, at each stage in the evolution of flight.

text: Feduccia is best known for his criticisms of the hypothesis, accepted by most paleontologists, that birds originated from and are deeply nested within

text: Theropoda

text: , and are therefore living

text: theropod

text: dinosaurs

text: .  Feduccia's first contribution relative to the origin and early evolution of birds, and their relationship with dinosaurs, was a critical review of the evidence then available for dinosaurian

text: endothermy

text: in 1973.  In a 1979 paper, Feduccia and

text: Tordoff

text: argued, against the position taken by

text: John Ostrom

text: , that

text: Archaeopteryx

text: was capable of powered flight, as indicated by the asymmetrical vanes of its primary

text: feathers

text: , a feature found only in flying birds.  In a paper coauthored with

text: Storrs Olson

text: in the same year, Feduccia noted that the robust

text: furcula

text: of

text: Archaeopteryx

text: could have served as a site of attachment for a well-developed M. pectoralis major, the principal depressor of the avian wing, responsible for powering the downstroke during avian flight.  Olson and Feduccia concluded that this provided further evidence for the flight capability of Archaeopteryx.  These initial excursions into the subject, and the argument that

text: Archaeopteryx

text: was clearly a bird, albeit primitive, were expanded upon in Feduccia's 1980 book, The Age of Birds.  Feduccia here criticized the theropod hypothesis for the origin of birds, but his position was largely agnostic, conceding that there was evidence in support of both a theropod ancestry of birds and an ancestry from more basal

text: archosaurs

text: , perhaps similar in overall morphological organization to

text: Euparkeria

text: .  Feduccia nevertheless suggested that on the basis of closer stratigraphic fit, ancestry from basal

text: archosaurs

text: rather than from

text: coelurosaurian

text: theropods

text: might prove a better phylogenetic hypothesis.  He thus, essentially, agreed with the model for the origin of birds proposed by

text: Gerhard Heilmann

text: in his influential 1926 book

text: The Origin of Birds

text: .  Feduccia also criticized "ground-up" theories for the origin of avian flight, arguing on biophysical grounds that they were implausible, and noting that in other cases in which flight has developed among vertebrates it has occurred in an arboreal context.  He argued, instead, for a "trees-down" model for the origin of avian flight due to its lack of the biophysical constraints hindering "ground-up" acquisition of flight and due to the ability to call upon biologically functional stages, represented by living analogues, at each stage in the evolution of flight.

text: miR-214 is a vertebrate-specific miR family that possesses one member in non-teleost vertebrates and two members in teleost fish. miR-214 is likely to have emerged within the Dnm3 gene after the divergence of jawed and jawless vertebrates and is located on the opposite strand of an intron of Dnm3 and is associated in an expression cluster with miR-199.

text: miR-214 is a vertebrate-specific miR family that possesses one member in non-teleost vertebrates and two members in teleost fish. miR-214 is likely to have emerged within the

text: gene after the divergence of

text: jawed

text: and

text: jawless vertebrates

text: and is located on the opposite strand of an intron of Dnm3 and is associated in an expression cluster with

text: Females of this species often undergo parthenogenesis. A male specimen was not noted until 2002. A few years later, a sexually reproducing strain was found.

text: Females of this species often undergo

text: parthenogenesis

text: . A male specimen was not noted until 2002. A few years later, a sexually reproducing strain was found.

text: The significant increase in the size of the cerebral hemisphere through evolution has been made possible in part through the evolution of the vascular pia mater, which allows nutrient blood vessels to penetrate deep into the intertwined cerebral matter, providing the necessary nutrients in this larger neural mass.  Throughout the course of life on earth, the nervous system of animals has continued to evolve to a more compact and increased organization of neurons and other nervous system cells.  This process is most evident in vertebrates and especially mammals in which the increased size of the brain is generally condensed into a smaller space through the presence of sulci or fissures on the surface of the hemisphere divided into gyri allowing more superficies of the cortical grey matter to exist.  The development of the meninges and the existence of a defined pia mater was first noted in the vertebrates, and has been more and more significant membrane in the brains of mammals with larger brains.

text: The story for fish is more complex. In teleost fish (which make up the great majority of existing species), the forebrain is distorted in comparison to other types of vertebrates: Most neuroanatomists believe that the teleost forebrain is in essence everted, like a sock turned inside-out, so that structures that lie in the interior, next to the ventricles, for most vertebrates, are found on the outside in teleost fish, and vice versa. One of the consequences of this is that the medial pallium ("hippocampal" zone) of a typical vertebrate is thought to correspond to the lateral pallium of a typical fish. Several types of fish (particularly goldfish) have been shown experimentally to have strong spatial memory abilities, even forming "cognitive maps" of the areas they inhabit. There is evidence that damage to the lateral pallium impairs spatial memory.

text: The story for fish is more complex. In

text: teleost

text: fish (which make up the great majority of existing species), the forebrain is distorted in comparison to other types of vertebrates: Most neuroanatomists believe that the teleost forebrain is in essence everted, like a sock turned inside-out, so that structures that lie in the interior, next to the ventricles, for most vertebrates, are found on the outside in teleost fish, and vice versa. One of the consequences of this is that the medial pallium ("hippocampal" zone) of a typical vertebrate is thought to correspond to the lateral pallium of a typical fish. Several types of fish (particularly goldfish) have been shown experimentally to have strong spatial memory abilities, even forming "cognitive maps" of the areas they inhabit. There is evidence that damage to the lateral pallium impairs spatial memory.

text: Like all Plasmodium species P. uilenbergi has both vertebrate and insect hosts. The vertebrate hosts for this parasite are mammals.

text: Like all Plasmodium species P. uilenbergi has both

text: vertebrate

text: and

text: insect

text: mammal

text: s.

text: Vision is the most important sense for birds, since good eyesight is essential for safe flight, and this group has a number of adaptations which give visual acuity superior to that of other vertebrate groups; a pigeon has been described as "two eyes with wings". The avian eye resembles that of a reptile, with ciliary muscles that can change the shape of the lens rapidly and to a greater extent than in the mammals. Birds have the largest eyes relative to their size in the animal kingdom, and movement is consequently limited within the eye's bony socket. In addition to the two eyelids usually found in vertebrates, it is protected by a third transparent movable membrane. The eye's internal anatomy is similar to that of other vertebrates, but has a structure, the pecten oculi, unique to birds.

text: Vision is the most important sense for

text: bird

text: s, since good eyesight is essential for safe flight, and this group has a number of adaptations which give visual acuity superior to that of other

text: vertebrate

text: groups; a pigeon has been described as "two eyes with wings". The avian eye resembles that of a

text: reptile

text: , with

text: ciliary muscles

text: that can change the shape of the

text: lens

text: rapidly and to a greater extent than in the

text: mammal

text: s. Birds have the largest eyes relative to their size in the animal kingdom, and movement is consequently limited within the eye's bony socket. In addition to the two eyelids usually found in vertebrates, it is protected by a third transparent movable membrane. The eye's internal anatomy is similar to that of other vertebrates, but has a structure, the

text: pecten oculi

text: , unique to birds.

text: In common parlance, endotherms are characterized as "warm-blooded." The opposite of endothermy is ectothermy, although there is no absolute or clear separation between the nature of endotherms and ectotherms in general.

text: In common parlance, endotherms are characterized as "

text: warm-blooded

text: ." The opposite of endothermy is

text: ectothermy

text: , although there is no absolute or clear separation between the nature of endotherms and ectotherms in general.

text: The Popeye (POP) family of proteins, is restricted to vertebrates and is preferentially expressed in developing and adult striated muscle. It is represented by a conserved region which includes three potential transmembrane domains. The strong conservation of POP genes during evolution and their preferential expression in heart and skeletal muscle suggest that these novel proteins may have an important function in these tissues in vertebrates.

text: Basal Ichthyopterygia, like their land-dwelling ancestors, still had vertebrae that possessed a full set of processes that allowed them to interlock and articulate forming a vertebral column supporting the weight of the body. As ichthyosaurs were fully aquatic, their bodies were supported by the Archimedes force exerted by the water; in other words: they were buoyant. Therefore, the vertebral processes had lost much of their function. Early ichthyosaurs proper had rear dorsal vertebrae that had become disc-shaped, like those of typical fishes. With more derived species, the front dorsals also became discs. Gradually, most processes were lost, including those for rib attachment. The vertebral bodies became much shorter. The front and rear sides of the discs were hollowed out, resulting in a so-called amphicoelous condition. A transverse cross-section of such a vertebra has an hourglass-shape. This morphology is unique within the Amniota and makes it easy to discern ichthyosaur vertebrae from those of other marine reptiles. The only process that kept its function was the spine at the top, serving as an attachment for the dorsal muscles. However, even the spine became a simple structure. The neural arch, of which it was an out-growth, typically no longer fused to the vertebral centre.

text: Basal Ichthyopterygia, like their land-dwelling ancestors, still had

text: vertebrae

text: that possessed a full set of processes that allowed them to interlock and articulate forming a

text: vertebral column

text: supporting the weight of the body. As ichthyosaurs were fully aquatic, their bodies were supported by the

text: Archimedes force

text: exerted by the water; in other words: they were

text: buoyant

text: . Therefore, the vertebral processes had lost much of their function. Early ichthyosaurs proper had rear dorsal vertebrae that had become disc-shaped, like those of typical fishes. With more derived species, the front dorsals also became discs. Gradually, most processes were lost, including those for rib attachment. The vertebral bodies became much shorter. The front and rear sides of the discs were hollowed out, resulting in a so-called

text: amphicoelous

text: condition. A transverse cross-section of such a vertebra has an hourglass-shape. This morphology is unique within the

text: Amniota

text: and makes it easy to discern ichthyosaur vertebrae from those of other marine reptiles. The only process that kept its function was the spine at the top, serving as an attachment for the dorsal muscles. However, even the spine became a simple structure. The

text: neural arch

text: , of which it was an out-growth, typically no longer fused to the vertebral centre.

text: Eyes in various animals show adaptation to their requirements. For example, the eye of a bird of prey has much greater visual acuity than a human eye, and in some cases can detect ultraviolet radiation. The different forms of eye in, for example, vertebrates and molluscs are examples of parallel evolution, despite their distant common ancestry. Phenotypic convergence of the geometry of cephalopod and most vertebrate eyes creates the impression that the vertebrate eye evolved from an imaging cephalopod eye, but this is not the case, as the reversed roles of their respective ciliary and rhabdomeric opsin classes and different lens crystallins show.

text: Eyes in various animals show adaptation to their requirements. For example, the eye of a

text: bird of prey

text: has much greater visual acuity than a

text: human eye

text: , and in some cases can detect

text: ultraviolet

text: radiation. The different forms of eye in, for example, vertebrates and molluscs are examples of

text: parallel evolution

text: , despite their distant common ancestry. Phenotypic convergence of the geometry of cephalopod and most vertebrate eyes creates the impression that the vertebrate eye evolved from an imaging

text: cephalopod eye

text: , but this is not the case, as the reversed roles of their respective ciliary and rhabdomeric opsin classes and different lens crystallins show.

text: Both basilosaurids have skeletons that are immediately recognizable as cetaceans. A basilosaurid was as big as the larger modern whales, with genera like Basilosaurus reaching lengths of up to  long; dorudontines were smaller, with genera like Dorudon reaching about  long.  The large size of basilosaurids is due to the extreme elongation of their lumbar vertebrae. They had a tail fluke, but their body proportions suggest that they swam by caudal undulation and that the fluke was not used for propulsion. In contrast, dorudontines had a shorter but powerful vertebral column. They too had a fluke and, unlike basilosaurids, they probably swam similarly to modern cetaceans, by using caudal oscillations. The forelimbs of basilosaurids were probably flipper-shaped, and the external hind limbs were tiny and were certainly not involved in locomotion. Their fingers, however, retained the mobile joints of their ambulocetid relatives. The two tiny but well-formed hind legs of basilosaurids were probably used as claspers when mating. The pelvic bones associated with these hind limbs were not connected to the vertebral column as they were in protocetids. Essentially, any sacral vertebrae can no longer be clearly distinguished from the other vertebrae.

text: Both basilosaurids have skeletons that are immediately recognizable as cetaceans. A basilosaurid was as big as the larger modern whales, with genera like Basilosaurus reaching lengths of up to  long; dorudontines were smaller, with genera like Dorudon reaching about  long.  The large size of basilosaurids is due to the extreme elongation of their lumbar vertebrae. They had a tail fluke, but their body proportions suggest that they swam by caudal undulation and that the fluke was not used for propulsion. In contrast, dorudontines had a shorter but powerful vertebral column. They too had a fluke and, unlike basilosaurids, they probably swam similarly to modern cetaceans, by using caudal oscillations. The forelimbs of basilosaurids were probably flipper-shaped, and the external hind limbs were tiny and were certainly not involved in locomotion. Their fingers, however, retained the mobile joints of their ambulocetid relatives. The two tiny but well-formed hind legs of basilosaurids were probably used as

text: clasper

text: s when mating. The pelvic bones associated with these hind limbs were not connected to the vertebral column as they were in protocetids. Essentially, any sacral vertebrae can no longer be clearly distinguished from the other vertebrae.

text: Denton suggested that these data undermined the notion that fish were ancestral to frogs, which were ancestral to reptiles, which were ancestral to birds and mammals. If they were, then wouldn't the difference in cytochrome C structures be increasingly different from carp to frog, to reptile, to mammal? How could the cytochrome c amino acid sequences for such a wide range of species all be "equidistant" from the sequence for bacteria? Molecular biologists quickly pointed out the fallacy in Denton's argument. Just as there is no such thing as a "living fossil", and all modern species are cousins, so too, the amino acid sequences for all living species have been evolving since the time of their divergence from a common ancestor. A modern carp is not an ancestor to a frog; frogs are not ancestors to turtles; turtles are not ancestors to rabbits. Similarly, the variations in eukaryotic cytochrome c structure with respect to bacteria are all due to mutations taking place since divergence from the common ancestor of these different organisms. It thus is not surprising that they show a similar level of divergence and equidistance of this type was even predicted and confirmed by researchers as early as 1963.

text: This extracellular endopeptidase is present in vertebrate tissues.

text: This extracellular

text: endopeptidase

text: is present in

text: vertebrate

text: tissues.

text: Ossicles are created intracellularly by specialised secretory cells known as sclerocytes in the dermis of the body wall of echinoderms. Each ossicle is composed of microcrystals of calcite arranged in a three-dimensional lattice known as a stereom. Under polarized light the ossicle behaves as if it were a single crystal because the axes of all the crystals are parallel. The space between the crystals is known as the stroma and allows entry to sclerocytes for enlargement and repair. The honeycomb structure is light but tough and collagenous ligaments connect the ossicles together. The ossicles are embedded in a tough connective tissue which is also part of the endoskeleton. When an ossicle becomes redundant, specialised cells known as phagocytes are able to reabsorb the calcareous material. All the ossicles, even those that protrude from the body wall, are covered by a thin layer of epidermis but functionally they act more like an exoskeleton than an endoskeleton.

text: Ossicles are created intracellularly by specialised secretory cells known as

text: sclerocyte

text: s in the

text: dermis

text: of the body wall of echinoderms. Each ossicle is composed of microcrystals of

text: calcite

text: arranged in a three-dimensional lattice known as a

text: stereom

text: . Under

text: polarized light

text: the ossicle behaves as if it were a single crystal because the axes of all the crystals are parallel. The space between the crystals is known as the

text: stroma

text: and allows entry to sclerocytes for enlargement and repair. The honeycomb structure is light but tough and

text: collagen

text: ous

text: ligament

text: s connect the ossicles together. The ossicles are embedded in a tough connective tissue which is also part of the endoskeleton. When an ossicle becomes redundant, specialised cells known as

text: phagocyte

text: s are able to reabsorb the calcareous material. All the ossicles, even those that protrude from the body wall, are covered by a thin layer of

text: epidermis

text: but functionally they act more like an

text: exoskeleton

text: than an endoskeleton.

text: Like all Plasmodium species P. lophurae has both vertebrate and insect hosts. The vertebrate hosts for this parasite are birds.

text: Like all Plasmodium species P. lophurae has both

text: vertebrate

text: and

text: insect

text: bird

text: s.

text: In the vertebrate spinal column, each vertebra is an irregular bone with a complex structure composed of bone and some hyaline cartilage, the proportions of which vary according to the segment of the backbone and the species of vertebrate.

text: In the vertebrate

text: spinal column

text: , each vertebra is an

text: irregular bone

text: with a complex structure composed of

text: bone

text: and some

text: hyaline cartilage

text: , the proportions of which vary according to the segment of the

text: backbone

text: and the species of

text: vertebrate

text: Protists generally reproduce asexually under favorable environmental conditions, but tend to reproduce sexually under stressful conditions, such as starvation or heat shock.

text: Templeton also studied the vertebrates of the island, especially the fish, birds and monkeys. Amongst the birds were five endemic species new to science. These were described by Edward Blyth in the Calcutta Journal as Athene castanotus, the chestnut-winged hawk owl; Malacocercus rufescens, the red dung thrush; Dicrurus edoliformis, the kingcrow, Dicrurus leucopyygialis the Ceylon kingcrow, and Eulabes ptilogenes, Templeton's mynah. The monkeys were studiously appraised and some of the results communicated to the Zoological Society of London. These communications, one of the monkey Cercopithecus pileatus and the loris Loris gracilis and the other on a supposed new species Semnopithecus leucoprymnus cephalopterus which turned out to be identical with Bennet's Semnopithecus nestor, are Templetons only personal contribution to the literature on the vertebrates of Ceylon. His knowledge of the smaller mammals, birds, reptiles and fishes was instead incorporated in the work of others, notably George Robert Waterhouse and his coworker Edgar Leopold Layard who in the introduction to Notes on the Ornithology of Ceylon says "I have had the advantage of consulting with Mr. Blyth and Drs. Templeton and Kelaart with each of whom i have been on terms of the closest intimacy and we mutually communicated our discoveries".

text: Templeton also studied the

text: vertebrate

text: s of the island, especially the fish,

text: bird

text: s and

text: monkey

text: s. Amongst the birds were five endemic species new to science. These were described by

text: Edward Blyth

text: in the Calcutta Journal as

text: Athene castanotus

text: , the chestnut-winged hawk owl;

text: Malacocercus rufescens

text: , the red dung thrush;

text: Dicrurus edoliformis

text: , the kingcrow,

text: Dicrurus leucopyygialis

text: the Ceylon kingcrow, and

text: Eulabes ptilogenes

text: , Templeton's mynah. The monkeys were studiously appraised and some of the results communicated to the Zoological Society of London. These communications, one of the monkey Cercopithecus pileatus and the loris Loris gracilis and the other on a supposed new species Semnopithecus leucoprymnus cephalopterus which turned out to be identical with Bennet's

text: Semnopithecus nestor

text: , are Templetons only personal contribution to the literature on the vertebrates of Ceylon. His knowledge of the smaller mammals, birds, reptiles and fishes was instead incorporated in the work of others, notably

text: George Robert Waterhouse

text: and his coworker

text: Edgar Leopold Layard

text: who in the introduction to Notes on the Ornithology of Ceylon says "I have had the advantage of consulting with Mr. Blyth and Drs. Templeton and Kelaart with each of whom i have been on terms of the closest intimacy and we mutually communicated our discoveries".

text: According to the Talmud, a shofar may be made from the horn of any animal from the Bovidae family except that of a cow although a ram is preferable. Bovidae horns are made of a layer of keratin (the same material as human toenails and fingernails) around a core of bone, with a layer of cartilage in between, which can be removed to leave the hollow keratin horn. An antler, on the other hand, is made of solid bone, so an antler cannot be used as a shofar because it cannot be hollowed out.

text: According to the Talmud, a shofar may be made from the horn of any animal from the

text: Bovid

text: ae family except that of a cow although a ram is preferable. Bovidae horns are made of a layer of

text: keratin

text: (the same material as human toenails and fingernails) around a core of bone, with a layer of cartilage in between, which can be removed to leave the hollow keratin horn. An

text: antler

text: , on the other hand, is made of solid bone, so an antler cannot be used as a shofar because it cannot be hollowed out.

text: Like all Plasmodium species P. neusticuri has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. neusticuri has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: The aquatic to terrestrial transition of vertebrate organisms occurred in the late Devonian era and was an important step in the evolutionary history of modern land vertebrates. The transition allowed animals to escape competitive pressure from the water and explore niche opportunities on land. Fossils from this period have allowed scientists to identify some of the species that existed during this transition, such as Tiktaalik and Acanthostega. Many of these species were also the first to develop adaptations suited to terrestrial over aquatic life, such as neck mobility and hindlimb locomotion.

text: The aquatic to terrestrial transition of

text: vertebrate

text: organisms occurred in the late

text: Devonian

text: era and was an important step in the evolutionary history of modern land vertebrates. The transition allowed animals to escape

text: competitive pressure

text: from the water and explore

text: niche

text: opportunities on land. Fossils from this period have allowed scientists to identify some of the species that existed during this transition, such as

text: Tiktaalik

text: and

text: Acanthostega

text: . Many of these species were also the first to develop adaptations suited to terrestrial over aquatic life, such as neck mobility and hindlimb locomotion.

text: The Living Planet Index (LPI) is an indicator of the state of global biological diversity, based on trends in vertebrate populations of species from around the world.

text: The Living Planet Index (LPI) is an indicator of the state of global

text: biological diversity

text: , based on trends in

text: vertebrate

text: populations of species from around the world.

text: Self-avoidance has only recently been explored in the vertebrate brain development and mainly in the context of patterning neurites in the Inner plexiform layers (IPLs). In contrast to Drosophila, mouse DSCAMs are typical cell surface molecules, lacking the massive alternative splicing of the fly Dscam1 orthologous undergoes. So although DSCAMs may retain a conserved function in mediating self-avoidance in vertebrates, the absence of molecular diversity makes it clear that they do not play a role in self-recognition.

text: Self-avoidance has only recently been explored in the vertebrate brain development and mainly in the context of patterning neurites in the

text: Inner plexiform layer

text: s (IPLs). In contrast to Drosophila, mouse DSCAMs are typical cell surface molecules, lacking the massive

text: alternative splicing

text: of the fly Dscam1 orthologous undergoes. So although DSCAMs may retain a conserved function in mediating self-avoidance in vertebrates, the absence of molecular diversity makes it clear that they do not play a role in self-recognition.

text: Romer was very keen in investigating vertebrate evolution. Comparing facts from paleontology, comparative anatomy, and embryology, he taught the basic structural and functional changes that happened during the evolution of fishes to primitive terrestrial vertebrates and from these to all other tetrapods. He always emphasized the evolutionary significance of the relationship between the form and function of animals and the environment.

text: Romer was very keen in investigating vertebrate evolution. Comparing facts from

text: paleontology

text: , comparative

text: anatomy

text: , and

text: embryology

text: , he taught the basic structural and functional changes that happened during the

text: evolution of fish

text: es to primitive terrestrial

text: vertebrate

text: s and from these to all other

text: tetrapod

text: s. He always emphasized the evolutionary significance of the relationship between the form and function of animals and the environment.

text: Vertebrae articulate with each other to  give strength and flexibility to the spinal column, and the shape at their back and front aspects determines the range of movement. Structurally, vertebrae are essentially alike across the vertebrate species, with the greatest difference seen between an aquatic animal and other vertebrate animals. As such, vertebrates take their name from the vertebrae that compose the vertebral column.

text: Vertebrae articulate with each other to  give strength and flexibility to the spinal column, and the shape at their back and front aspects determines the range of movement. Structurally, vertebrae are essentially alike across the vertebrate species, with the greatest difference seen between an

text: aquatic animal

text: and other vertebrate animals. As such, vertebrates take their name from the vertebrae that compose the

text: vertebral column

text: Various patterns of behavior enable certain ectotherms to regulate body temperature to a useful extent. To warm up, reptiles and many insects find sunny places and adopt positions that maximise their exposure; at harmfully high temperatures they seek shade or cooler water. In cold weather, honey bees huddle together to retain heat. Butterflies and moths may orient their wings to maximize exposure to solar radiation in order to build up heat before take-off. Gregarious caterpillars, such as the Forest Tent caterpillar, benefit from basking in large groups for thermoregulation. Many flying insects, such as honey bees and bumble bees, also raise their internal temperatures endothermally prior to flight, by vibrating their flight muscles without violent movement of the wings (see insect thermoregulation). Such endothermal activity is an example of the difficulty of consistent application of terms such as poikilothermy and homiothermy.

text: Various patterns of behavior enable certain ectotherms to regulate body temperature to a useful extent. To warm up, reptiles and many insects find sunny places and adopt positions that maximise their exposure; at harmfully high temperatures they seek shade or cooler water. In cold weather, honey bees huddle together to retain heat. Butterflies and moths may orient their wings to maximize exposure to solar radiation in order to build up heat before take-off. Gregarious caterpillars, such as the

text: Forest Tent caterpillar

text: , benefit from basking in large groups for thermoregulation. Many flying insects, such as honey bees and bumble bees, also raise their internal temperatures endothermally prior to flight, by vibrating their flight muscles without violent movement of the wings (see

text: insect thermoregulation

text: ). Such endothermal activity is an example of the difficulty of consistent application of terms such as poikilothermy and homiothermy.

text: Although the word dinosaur literally means "terrible lizard", the name is something of an etymological misnomer; even though dinosaurs are reptiles, they are not lizards, nor are they descended from them. Instead, dinosaurs, like many extinct forms of reptile sub-groups, did not exhibit characteristics which were traditionally regarded as reptilian, such as a sprawling limb posture or ectothermy (colloquially referred to as "cold-bloodedness"). Additionally, many other prehistoric animals, including mosasaurs, ichthyosaurs, pterosaurs, plesiosaurs, and Dimetrodon, while often popularly conceived of as dinosaurs, are not taxonomically classified as dinosaurs.

text: Although the word dinosaur literally means "terrible lizard", the name is something of an etymological

text: misnomer

text: ; even though dinosaurs are

text: reptiles

text: , they are not

text: lizards

text: , nor are they descended from them. Instead, dinosaurs, like many extinct forms of reptile sub-groups, did not exhibit characteristics which were traditionally regarded as reptilian, such as a

text: sprawling limb posture

text: or

text: ectothermy

text: (colloquially referred to as "cold-bloodedness"). Additionally, many other prehistoric animals, including

text: mosasaur

text: s,

text: ichthyosaur

text: s,

text: pterosaur

text: s,

text: plesiosaur

text: s, and

text: Dimetrodon

text: , while often popularly conceived of as dinosaurs, are not

text: taxonomically

text: classified as dinosaurs.

text: Like all Plasmodium species P. paranucleophilum has both vertebrate and insect hosts. The vertebrate hosts for this parasite are birds.

text: Like all Plasmodium species P. paranucleophilum has both

text: vertebrate

text: and

text: insect

text: bird

text: s.

text: The cephalopods have a non-inverted retina which is comparable in resolving power to the eyes of many vertebrates. Squid eyes do not have an analog of the vertebrate RPE. Although their photoreceptors contain a protein, retinochrome, that recycles retinal and replicates one of the functions of the vertebrate RPE, one could argue that the photoreceptor as a whole is not maintained as well overall in cephalopods as in vertebrates. As a result, the useful lifetime of photoreceptors in invertebrates is much shorter than in vertebrates.  A third possibility, of having easily replaced stalk-eyes (some lobsters) or retinae (some spiders, such as Deinopis) is rare.

text: By the 18th century, references to fish were hard to find in the Fishmongers' Company Court minutes, since the Company's main business had evolved into managing its extensive properties and administering its charities and trusts, such as Gresham's School as well as St. Peter's Hospital and almshouses at Newington in Surrey.

text: By the 18th century, references to fish were hard to find in the Fishmongers' Company Court minutes, since the Company's main business had evolved into managing its extensive properties and administering its charities and trusts, such as

text: Gresham's School

text: as well as

text: St. Peter's Hospital

text: and

text: almshouse

text: s at

text: Newington

text: in Surrey.

text: A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (Ancient Greek an-, without + oura, tail). The oldest fossil "proto-frog" appeared in the early Triassic of Madagascar, but molecular clock dating suggests their origins may extend further back to the Permian, 265 million years ago. Frogs are widely distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is in tropical rainforests. There are approximately 4,800 recorded species, accounting for over 85% of extant amphibian species. They are also one of the five most diverse vertebrate orders.

text: A frog is any member of a diverse and largely

text: carnivorous

text: group of short-bodied, tailless

text: amphibian

text: s composing the

text: order

text: Anura (

text: Ancient Greek

text: an-, without + oura, tail). The

text: oldest fossil "proto-frog"

text: appeared in the

text: early Triassic

text: of

text: Madagascar

text: , but

text: molecular clock dating

text: suggests their origins may extend further back to the

text: Permian

text: , 265 million years ago. Frogs are widely distributed, ranging from the

text: tropics

text: to

text: subarctic

text: regions, but the greatest concentration of

text: species diversity

text: is in

text: tropical rainforest

text: s. There are approximately 4,800 recorded species, accounting for over 85% of extant amphibian species. They are also one of the five most diverse

text: vertebrate

text: orders.

text: The cranial endoskeleton of T. roseae shares derived features with tetrapods. There was a loss of opercular and extrascapular elements, enhancing head mobility in T. roseae compared to other tetrapodomorph fish. The formation of the neck allowed for locomotion in shallow waters. This environment allows for less motility compared to the three-dimensional space that fish are able to orient themselves in. The body of the organism in these environments would be fixed in the shallow pools with appendages planted on a substrate.

text: The Bone Valley Formation includes a diverse assemblage of vertebrate fossils. These include remains sea turtles, equines, felines, peccaries, and others.

text: The Bone Valley Formation includes a diverse assemblage of vertebrate fossils. These include remains

text: sea turtle

text: s,

text: equine

text: s,

text: felines

text: peccaries

text: , and others.

text: The organism's evolutionary placement and unique embryology with five-fold symmetry were the major arguments in the proposal to seek the sequencing of its genome. Importantly, urchins act as the closest living relative to chordates and thus may shed light on the evolution of vertebrates. The  genome of Strongylocentrotus purpuratus, was completed in 2006 and established homology between sea urchin and vertebrate immune system-related genes. Sea urchins code for at least 222 Toll-like receptor genes and over 200 genes related to the Nod-like-receptor family found in vertebrates. This increases its usefulness as a valuable model organism for studying the evolution of innate immunity. The sequencing also revealed that while some genes were thought to be limited to vertebrates, there were also innovations that have previously never been seen outside the chordate classification, such as immune transcription factors PU.1 and SPIB.

text: The organism's evolutionary placement and unique embryology with five-fold symmetry were the major arguments in the proposal to seek the sequencing of its genome. Importantly, urchins act as the closest living relative to chordates and thus may shed light on the evolution of

text: vertebrate

text: s. The

text: genome

text: of

text: Strongylocentrotus purpuratus

text: , was completed in 2006 and established homology between sea urchin and

text: vertebrate

text: immune system

text: -related genes. Sea urchins code for at least 222

text: Toll-like receptor

text: genes and over 200 genes related to the

text: Nod-like-receptor

text: family found in vertebrates. This increases its usefulness as a valuable model organism for studying the

text: evolution

text: of

text: innate immunity

text: . The sequencing also revealed that while some genes were thought to be limited to vertebrates, there were also innovations that have previously never been seen outside the chordate classification, such as immune transcription factors

text: and

text: SPIB

text: The rib cage is an arrangement of bones in the thorax of all vertebrates except the lamprey and the frog. It is formed by the vertebral column, ribs, and sternum and encloses the heart and lungs. In humans, the rib cage, also known as the thoracic cage, is a bony and cartilaginous structure which surrounds the thoracic cavity and supports the pectoral girdle (shoulder girdle), forming a core portion of the human skeleton. A typical human rib cage consists of 24 ribs, the sternum (with xiphoid process), costal cartilages, and the 12 thoracic vertebrae. Together with the skin and associated fascia and muscles,  the rib cage makes up the thoracic wall and provides attachments for the muscles of the neck, thorax, upper abdomen, and back.

text: The rib cage is an arrangement of

text: bone

text: s in the

text: thorax

text: of all

text: vertebrate

text: s except the

text: lamprey

text: and the

text: frog

text: . It is formed by the

text: vertebral column

text: rib

text: s, and

text: sternum

text: and encloses the

text: heart

text: and

text: lung

text: s. In humans, the rib cage, also known as the thoracic cage, is a bony and

text: cartilaginous

text: structure which surrounds the

text: thoracic cavity

text: and supports the

text: pectoral girdle

text: (shoulder girdle), forming a core portion of the

text: human skeleton

text: . A typical human rib cage consists of 24 ribs, the sternum (with

text: xiphoid process

text: costal cartilage

text: s, and the 12

text: thoracic vertebra

text: e. Together with the

text: skin

text: and associated

text: fascia

text: and

text: muscle

text: s,  the rib cage makes up the

text: thoracic wall

text: and provides attachments for the muscles of the neck, thorax, upper abdomen, and back.

text: Humans and some other mammals have evolved trichromacy based partly on pigments inherited from early vertebrates. In fish and birds, for example, four pigments are used for vision. These extra cone receptor visual pigments detect energy of other wavelengths, including sometimes ultraviolet. Eventually two of these pigments were lost (in placental mammals) and another was gained, resulting in trichromacy among some primates. Humans and closely related primates are usually trichromats, as are some of the females of most species of New World monkeys, and both male and female howler monkeys.

text: Humans and some other mammals have evolved trichromacy based partly on pigments inherited from early vertebrates. In fish and birds, for example, four pigments are used for vision. These extra cone receptor visual pigments detect energy of other wavelengths, including sometimes ultraviolet. Eventually two of these pigments were lost (in placental mammals) and another was gained, resulting in trichromacy among some primates.

text: Human

text: s and

text: closely related primates

text: are usually trichromats, as are some of the females of most species of

text: New World monkey

text: s, and both male and female

text: howler monkey

text: s.

text: Shark skeletons are very different from those of bony fish and terrestrial vertebrates. Sharks and other cartilaginous fish (skates and rays) have skeletons made of cartilage and connective tissue. Cartilage is flexible and durable, yet is about half the normal density of bone. This reduces the skeleton's weight, saving energy. Because sharks do not have rib cages, they can easily be crushed under their own weight on land.

text: Shark skeletons are very different from those of

text: bony fish

text: and

text: terrestrial vertebrates

text: . Sharks and other

text: cartilaginous fish

text: skate

text: s and

text: rays

text: ) have skeletons made of

text: cartilage

text: and

text: connective tissue

text: . Cartilage is flexible and durable, yet is about half the normal density of bone. This reduces the skeleton's weight, saving energy. Because sharks do not have rib cages, they can easily be crushed under their own weight on land.

text: Reproduction in snakes is almost exclusively sexual. Males ordinarily have a ZZ pair of sex determining chromosomes and females a ZW pair.  However, it was recently shown that E. maurus is capable of reproducing by facultative parthenogenesis resulting in production of WW female progeny.  The WW females were likely produced by terminal automixis (see diagram), a type of parthenogenesis in which two terminal haploid products of meiosis fuse to form a zygote, which then develops into a daughter progeny.  This is only the third genetically confirmed case of consecutive virgin births of viable offspring from a single female within any vertebrate lineage.

text: Reproduction in snakes is almost exclusively sexual. Males ordinarily have a ZZ pair of sex determining chromosomes and females a ZW pair.  However, it was recently shown that E. maurus is capable of reproducing by facultative

text: parthenogenesis

text: resulting in production of WW female progeny.  The WW females were likely produced by terminal automixis (see diagram), a type of parthenogenesis in which two terminal haploid products of meiosis fuse to form a zygote, which then develops into a daughter progeny.  This is only the third genetically confirmed case of consecutive virgin births of viable offspring from a single female within any vertebrate lineage.

text: Like vertebrates, most invertebrates reproduce at least partly through sexual reproduction. They produce specialized reproductive cells that undergo meiosis to produce smaller, motile spermatozoa or larger, non-motile ova. These fuse to form zygotes, which develop into new individuals. Others are capable of asexual reproduction, or sometimes, both methods of reproduction.

text: Like vertebrates, most invertebrates reproduce at least partly through

text: sexual reproduction

text: . They produce specialized

text: reproductive cells

text: that undergo

text: meiosis

text: to produce smaller, motile

text: spermatozoa

text: or larger, non-motile

text: ova

text: . These fuse to form

text: zygote

text: s, which develop into new individuals. Others are capable of asexual reproduction, or sometimes, both methods of reproduction.

text: Somites are bilaterally paired blocks of paraxial mesoderm that form along the head-to-tail axis of the developing embryo in segmented animals. In vertebrates, somites subdivide into the sclerotomes, myotomes and dermatomes that give rise to the vertebrae of the vertebral column, rib cage, and part of the occipital bone; skeletal muscle, cartilage, tendons, and skin (of the back).

text: Somites are bilaterally paired blocks of

text: paraxial mesoderm

text: that form along the head-to-tail axis of the developing embryo in

text: segmented

text: animals. In

text: vertebrate

text: s, somites subdivide into the sclerotomes, myotomes and dermatomes that give rise to the

text: vertebrae

text: of the

text: vertebral column

text: rib cage

text: , and part of the

text: occipital bone

text: skeletal muscle

text: cartilage

text: tendon

text: s, and

text: skin

text: (of the back).

text: New phylogenomic analysis shows urochordates, rather than cephalochordates, as the sister group to vertebrates. All OR genes were lost in the lineage of urochordata because of the absence of any vertebrate-type OR-like genes. The loss of vertebrate type OR-genes therefore suggests that they may have been lost in the urochodates genomes (lost genes conserved between amphioxus and vertebrates).

text: New phylogenomic analysis shows

text: urochordates

text: , rather than

text: cephalochordate

text: s, as the sister group to vertebrates. All OR genes were lost in the lineage of urochordata because of the absence of any vertebrate-type OR-like genes. The loss of vertebrate type OR-genes therefore suggests that they may have been lost in the urochodates genomes (lost genes conserved between

text: amphioxus

text: and vertebrates).

text: Even the groups that survived suffered extremely heavy losses of species, and some terrestrial vertebrate groups very nearly became extinct at the end-Permian. Some of the surviving groups did not persist for long past this period, while others that barely survived went on to produce diverse and long-lasting lineages. Yet it took 30million years for the terrestrial vertebrate fauna to fully recover both numerically and ecologically.

text: For example, the basal ganglia (structures derived from the floor of the forebrain and making up MacLean's reptilian complex) were shown to take up a much smaller portion of the forebrains of reptiles and birds (together called sauropsids) than previously supposed, and to exist in amphibians and fish as well as mammals and sauropsids. Because the basal ganglia are found in the forebrains of all modern vertebrates, they most likely date to the common evolutionary ancestor of the vertebrates, more than 500 million years ago, rather than to the origin of reptiles.

text: For example, the basal ganglia (structures derived from the floor of the forebrain and making up MacLean's reptilian complex) were shown to take up a much smaller portion of the forebrains of reptiles and birds (together called

text: sauropsids

text: ) than previously supposed, and to exist in

text: amphibians

text: and

text: fish

text: as well as

text: mammals

text: and sauropsids. Because the basal ganglia are found in the forebrains of all modern vertebrates, they most likely date to the common evolutionary ancestor of the vertebrates, more than 500 million years ago, rather than to the origin of reptiles.

text: Initial facial changes usually involve the area of the face covered by the temporal or buccinator muscles. The disease progressively spreads from the initial location, resulting in atrophy of the skin and its adnexa, as well as underlying subcutaneous structures such as connective tissue, (fat, fascia, cartilage, bones) and/or muscles of one side of the face. The mouth and nose are typically deviated towards the affected side of the face.

text: Initial facial changes usually involve the area of the face covered by the

text: temporal

text: or

text: buccinator muscle

text: s. The disease progressively spreads from the initial location, resulting in atrophy of the skin and its

text: adnexa

text: , as well as underlying subcutaneous structures such as

text: connective tissue

text: fat

text: fascia

text: cartilage

text: bones

text: ) and/or

text: muscles

text: of one side of the face. The mouth and nose are typically deviated towards the affected side of the face.

text: In the clade of vertebrates, legs are an advanced trait since it is a feature that appears in the clade. However, in the clade of tetrapods, legs are primitive since they were inherited from a common ancestor.

text: In the

text: clade

text: of vertebrates, legs are an advanced trait since it is a feature that appears in the clade. However, in the clade of tetrapods, legs are primitive since they were inherited from a common ancestor.

text: The arrangement in lampreys, which are among the most primitive of all fish, may indicate how the pituitary originally evolved in ancestral vertebrates. Here, the posterior pituitary is a simple flat sheet of tissue at the base of the brain, and there is no pituitary stalk. Rathke's pouch remains open to the outside, close to the nasal openings. Closely associated with the pouch are three distinct clusters of glandular tissue, corresponding to the intermediate lobe, and the rostral and proximal portions of the anterior pituitary. These various parts are separated by meningial membranes, suggesting that the pituitary of other vertebrates may have formed from the fusion of a pair of separate, but associated, glands.

text: The arrangement in

text: lamprey

text: s, which are among the most primitive of all fish, may indicate how the pituitary originally evolved in ancestral vertebrates. Here, the posterior pituitary is a simple flat sheet of tissue at the base of the brain, and there is no pituitary stalk. Rathke's pouch remains open to the outside, close to the nasal openings. Closely associated with the pouch are three distinct clusters of glandular tissue, corresponding to the intermediate lobe, and the rostral and proximal portions of the anterior pituitary. These various parts are separated by

text: meningial

text: membranes, suggesting that the pituitary of other vertebrates may have formed from the fusion of a pair of separate, but associated, glands.

text: In chiropractic, vertebral subluxation is a supposed misalignment of the spinal column leading to a set of signs and symptoms sometimes termed vertebral subluxation complex. It has no biomedical basis and is categorized as pseudoscientific by leading authorities. Traditionally, the "specific focus of chiropractic practice" is the chiropractic subluxation and historical chiropractic practice assumes that a vertebral subluxation or spinal joint dysfunction interferes with the body's function and its innate intelligence, as promulgated by D. D. Palmer, the inventor of chiropractic.

text: In

text: chiropractic

text: , vertebral subluxation is a supposed misalignment of the spinal column leading to a set of

text: signs and symptoms

text: sometimes termed vertebral subluxation complex. It has no

text: biomedical

text: basis and is categorized as

text: pseudoscientific

text: by leading authorities. Traditionally, the "specific focus of chiropractic practice" is the chiropractic subluxation and historical chiropractic practice assumes that a vertebral subluxation or

text: spinal joint

text: dysfunction interferes with the body's function and its

text: innate intelligence

text: , as promulgated by

text: D. D. Palmer

text: , the inventor of chiropractic.

text: Placodermi (from the Greek πλάξ = plate and δέρμα = skin, literally "plate-skinned") is an extinct class of armoured prehistoric fish, known from fossils, which lived from the Silurian to the end of the Devonian Period. Their head and thorax were covered by articulated armoured plates and the rest of the body was scaled or naked, depending on the species. Placoderms were among the first jawed fish; their jaws likely evolved from the first of their gill arches. Placoderms are paraphyletic, and consist of several distinct outgroups or sister taxa to all living jawed vertebrates, which originated among their ranks. This is illustrated by a 419-million-year-old fossil, Entelognathus, from China, which is the only known placoderm with a type of bony jaw like that found in modern bony fishes. This includes a dentary bone, which is found in humans and other tetrapods,. The jaws in other placoderms were simplified and consisted of a single bone. Placoderms were also the first fish to develop pelvic fins, the precursor to hindlimbs in tetrapods, as well as true teeth. 380-million-year-old fossils of three other genera, Incistoscutum, Materpiscis and Austroptyctodus,  represent the oldest known examples of live birth.

text: Placodermi (from the Greek πλάξ = plate and δέρμα = skin, literally "

text: plate

text: -skinned") is an

text: extinct

text: class

text: of armoured

text: prehistoric fish

text: , known from

text: fossil

text: s, which lived from the

text: Silurian

text: to the end of the

text: Devonian

text: Period. Their

text: head

text: and

text: thorax

text: were covered by articulated armoured plates and the rest of the body was

text: scaled

text: or naked, depending on the

text: species

text: . Placoderms were among the first

text: jawed fish

text: ; their

text: jaws

text: likely evolved from the first of their

text: gill arch

text: es. Placoderms are

text: paraphyletic

text: , and consist of several distinct

text: outgroups

text: or

text: sister taxa

text: to all living jawed

text: vertebrate

text: s, which originated among their ranks. This is illustrated by a 419-million-year-old fossil,

text: Entelognathus

text: , from

text: China

text: , which is the only known placoderm with a type of

text: bony

text: jaw like that found in modern

text: bony fishes

text: . This includes a

text: dentary bone

text: , which is found in humans and other

text: tetrapod

text: s,. The jaws in other placoderms were simplified and consisted of a single

text: bone

text: . Placoderms were also the first fish to develop

text: pelvic fin

text: s, the precursor to

text: hindlimb

text: s in tetrapods, as well as true

text: teeth

text: . 380-million-year-old fossils of three other genera, Incistoscutum, Materpiscis and

text: Austroptyctodus

text: ,  represent the oldest known examples of

text: live birth

text: Alfred Sherwood Romer (December 28, 1894 – November 5, 1973) was an American paleontologist and biologist and a specialist in vertebrate evolution.

text: Alfred Sherwood Romer (December 28, 1894 – November 5, 1973) was an American

text: paleontologist

text: and

text: biologist

text: and a specialist in

text: vertebrate

text: evolution

text: Vertebrate is closely related to the word vertebra, which refers to any of the bones or segments of the spinal column.

text: Vertebrate is closely related to the word

text: vertebra

text: , which refers to any of the bones or segments of the

text: spinal column

text: Prothero’s work on documenting evolutionary history of fossil vertebrates was cited by Richard Dawkins in his book The Greatest Show on Earth: the Evidence of Evolution. Skeptic Society founder Michael Shermer called Prothero's 2007 book, Evolution: What the Fossils Say And Why It Matters,  "the best book ever produced on the subject."

text: Prothero’s work on documenting evolutionary history of fossil vertebrates was cited by

text: Richard Dawkins

text: in his book The Greatest Show on Earth: the Evidence of Evolution. Skeptic Society founder

text: Michael Shermer

text: called Prothero's 2007 book, Evolution: What the Fossils Say And Why It Matters,  "the best book ever produced on the subject."

text: Mfge8 is secreted protein found in vertebrates, including mammals as well as birds.

text: Recent work has identified mutations in the hedgehog acyltransferase (HHAT) gene that have caused acrania along with holoprosencephaly and agnathia. The mutation in  which causes this disease is a loss-of-function mutation. Before this discovery in 2010, HHAT was known to play a role in the Sonic Hedgehog Pathway. When HHAT contains a loss-of-function mutation, less HHAT protein is produced.  is necessary for the production of Hedgehog () proteins post-transcriptionally. As HHAT production decreases, production of long-range Hh proteins decreases proportionally. Decreases in Hh| production disturb the production of extracellular signal-regulated kinases, bone morphogenetic proteins, and fibroblast growth factors, all of which play important roles in craniofacial patterning. Disruption of these pathways leads to abnormal bone and cartilage formation causing acrania and multiple other craniofacial patterning problems.

text: Recent work has identified mutations in the

text: hedgehog acyltransferase

text: (HHAT) gene that have caused acrania along with

text: holoprosencephaly

text: and

text: agnathia

text: . The mutation in

text: which causes this disease is a loss-of-function mutation. Before this discovery in 2010, HHAT was known to play a role in the

text: Sonic Hedgehog Pathway

text: . When HHAT contains a loss-of-function mutation, less HHAT protein is produced.  is necessary for the production of Hedgehog () proteins post-transcriptionally. As HHAT production decreases, production of long-range Hh proteins decreases proportionally. Decreases in Hh| production disturb the production of

text: extracellular signal-regulated kinases

text: bone morphogenetic protein

text: s, and

text: fibroblast growth factor

text: s, all of which play important roles in craniofacial patterning. Disruption of these pathways leads to abnormal bone and cartilage formation causing acrania and multiple other craniofacial patterning problems.

text: Like all Plasmodium species P. pulmophilium has both vertebrate and insect hosts. The vertebrate hosts for this parasite are mammals.

text: Like all Plasmodium species P. pulmophilium has both

text: vertebrate

text: and

text: insect

text: mammal

text: s.

text: Bakker and Ostrom both pointed out that all dinosaurs had erect hindlimbs and that all quadrupedal dinosaurs had erect forelimbs; and that among living animals only the endothermic ("warm-blooded") mammals and birds have erect limbs (Ostrom acknowledged that crocodilians' occasional "high walk" was a partial exception). Bakker claimed this was clear evidence of endothermy in dinosaurs, while Ostrom regarded it as persuasive but not conclusive.

text: Bakker and Ostrom both pointed out that all dinosaurs had erect hindlimbs and that all quadrupedal dinosaurs had erect forelimbs; and that among living animals only the endothermic ("warm-blooded") mammals and birds have erect limbs (Ostrom acknowledged that

text: crocodilian

text: s' occasional "high walk" was a partial exception). Bakker claimed this was clear evidence of endothermy in dinosaurs, while Ostrom regarded it as persuasive but not conclusive.

text: In general, external temperature does not influence endothermic animal behavior or circadian rhythm because of the ability of these animals to keep their internal body temperature constant through homeostatic thermoregulation; however, peripheral oscillators (see Circadian rhythm) in mammals are sensitive to temperature pulses and will experience resetting of the circadian clock phase and associated genetic expression, suggesting how peripheral circadian oscillators may be separate entities from one another despite having a master oscillator within the SCN. Furthermore, when individual neurons of the SCN from a mouse were treated with heat pulses, a similar resetting of oscillators was observed, but when an intact SCN was treated with the same heat pulse treatment the SCN was resistant to temperature change by exhibiting an unaltered circadian oscillating phase. In ectothermic  animals, particularly the ruin lizard Podacris sicula, temperature has been shown to affect the circadian oscillators within the SCN. This reflects a potential evolutionary relationship among endothermic and ectothermic vertebrates, in how ectotherms rely on environmental temperature to affect their circadian rhythms and behavior and endotherms have an evolved SCN to essentially ignore external temperature and use photoreception as a means for entraining the circadian oscillators within their SCN. In addition, the differences of the SCN between endothermic and ectothermic vertebrates suggest that the neuronal organization of the temperature-resistant SCN in endotherms is responsible for driving thermoregulatory behaviors in those animals differently from those of ectotherms, since they rely on external temperature for engaging in certain behaviors.

text: In general, external temperature does not influence endothermic animal behavior or circadian rhythm because of the ability of these animals to keep their internal body temperature constant through homeostatic thermoregulation; however, peripheral oscillators (see

text: Circadian rhythm

text: ) in mammals are sensitive to temperature pulses and will experience resetting of the circadian clock phase and associated genetic expression, suggesting how peripheral circadian oscillators may be separate entities from one another despite having a master oscillator within the SCN. Furthermore, when individual neurons of the SCN from a mouse were treated with heat pulses, a similar resetting of oscillators was observed, but when an intact SCN was treated with the same heat pulse treatment the SCN was resistant to temperature change by exhibiting an unaltered circadian oscillating phase. In ectothermic  animals, particularly the

text: ruin lizard

text: Podacris sicula, temperature has been shown to affect the circadian oscillators within the SCN. This reflects a potential evolutionary relationship among endothermic and ectothermic vertebrates, in how ectotherms rely on environmental temperature to affect their circadian rhythms and behavior and endotherms have an evolved SCN to essentially ignore external temperature and use photoreception as a means for entraining the circadian oscillators within their SCN. In addition, the differences of the SCN between endothermic and ectothermic vertebrates suggest that the neuronal organization of the temperature-resistant SCN in endotherms is responsible for driving thermoregulatory behaviors in those animals differently from those of ectotherms, since they rely on external temperature for engaging in certain behaviors.

text: The introduction of the Nile perch had a decisive impact on Haplochromis stocks which it favoured as its prey, affecting both their abundance and diversity. It is believed that the contribution of this species flock to the fish biomass of the lake has decreased from 80% to less than 1% since the introduction of the Nile perch, and that some 65% of the Haplochromis species were driven to extinction in the process, an event which may well represent the largest extinction event amongst vertebrates in the 20th century.

text: The introduction of the Nile perch had a decisive impact on Haplochromis stocks which it favoured as its prey, affecting both their abundance and diversity. It is believed that the contribution of this species flock to the fish biomass of the lake has decreased from 80% to less than 1% since the introduction of the Nile perch, and that some 65% of the Haplochromis species were driven to extinction in the process, an event which may well represent the largest

text: extinction event

text: amongst vertebrates in the 20th century.

text: This theory was popularized by Scott in 1950s and states that cartilage determines the craniofacial growth. Proponents of this theory state that cartilage is responsible for the growth and bone just replaced it. In this theory, mandibular condyle having cartilage at its end allows the downward and forward growth of the mandible. Maxilla, compromising of nasal septum and Nasomaxillary complex which is made up of cartilage, moves forward and downward also by the forces from the nasal septum. Bones in both maxilla and mandible respond to their respective cartilaginous growth centers. To test this theory, two approaches were taken by researchers in past. Either the cartilage was removed from the nasal septum or the cartilage was transplanted into the cultures to see the effects on the growth. When the cartilage was transplanted into the in vitro cultures, it was found that the cartilage from nasal septum grew as nearly as it did in vivo. In comparison, cartilage from mandibular condyle did not grew as well. Therefore, cartilage at condyle, cranial base synchondroses and nasal septum can act as growth centers.

text: This theory was popularized by Scott in 1950s and states that cartilage determines the craniofacial growth. Proponents of this theory state that cartilage is responsible for the growth and bone just replaced it. In this theory, mandibular condyle having cartilage at its end allows the downward and forward growth of the mandible. Maxilla, compromising of nasal septum and

text: Nasomaxillary complex

text: which is made up of cartilage, moves forward and downward also by the forces from the nasal septum. Bones in both maxilla and mandible respond to their respective cartilaginous growth centers. To test this theory, two approaches were taken by researchers in past. Either the cartilage was removed from the nasal septum or the cartilage was transplanted into the cultures to see the effects on the growth. When the cartilage was transplanted into the in vitro cultures, it was found that the cartilage from nasal septum grew as nearly as it did in vivo. In comparison, cartilage from mandibular condyle did not grew as well. Therefore, cartilage at condyle, cranial base synchondroses and nasal septum can act as growth centers.

text: The border mountains of Guizhou, Guangxi, and Hunan have been identified as one of the eight plant diversity hotspots in China. The main ecosystem types include evergreen broad-leaved forest, coniferous and broad-leaved mixed forest, and montane elfin forest. Plant species endemic to this region include Abies ziyuanensis, Cathaya argyrophylla, and Keteleeria pubescens. In broad terms, the Yunnan-Guizhou Plateau is one of the vertebrate diversity hotspots of China. At the level of counties, Xingyi is one of nine Chinese vertebrate diversity (excluding birds) hotspots. Animals only known from Guizhou include Leishan moustache toad, Kuankuoshui salamander, Shuicheng salamander, Guizhou salamander, and Zhijin warty newt.

text: The border mountains of Guizhou, Guangxi, and Hunan have been identified as one of the eight plant diversity hotspots in China. The main ecosystem types include evergreen broad-leaved forest, coniferous and broad-leaved mixed forest, and montane elfin forest. Plant species

text: endemic

text: to this region include

text: Abies ziyuanensis

text: Cathaya argyrophylla

text: , and

text: Keteleeria pubescens

text: . In broad terms, the

text: Yunnan-Guizhou Plateau

text: is one of the vertebrate diversity hotspots of China. At the level of counties,

text: Xingyi

text: is one of nine Chinese vertebrate diversity (excluding birds) hotspots. Animals only known from Guizhou include

text: Leishan moustache toad

text: Kuankuoshui salamander

text: Shuicheng salamander

text: Guizhou salamander

text: , and

text: Zhijin warty newt

text: Other distinctive traits are related to the tusk whorls on the lower jaw. Because they could rotate, this was a different method of jaw articulation which did not compare with primitive ray-finned fish. The lower jaw was entirely articulated with cartilage, without an intermediate structure between the opposite sides, allowing the separation of the bones when prey was struck. Moreover, the loose articulation caused lateral movement, making the tusk walls move out of alignment. The parts of the lower jaw would have rotated inwards upon closing in order for the tusk whorls to fit exactly into the hollow spaces in the upper jaw. It is suggested that a ligament attachment and retractor mechanism existed in a pit under the tusk whorl, a unique condition in vertebrates. The capacity of the teeth on the lower jaw to fit with the tooth rows in the upper jaw, upon closure, kept the tusk whorls in place.

text: Spirometra is a genus of Pseudophyllid cestode that reproduces in canines and felines but which can cause pathology in humans.  As an adult, this tapeworm lives in the small intestine of its definitive host and produces eggs that pass with the animal's feces.  The eggs hatch into coracidia which are eaten by copepods which become infected themselves.  In the copepod, the worm forms a procercoid, which is infective to vertebrates that ingest them.  Often, because the copepods are so small, vertebrates ingest copepods accidentally by drinking them.  In the vertebrate, the worms enter the plerocercoid stage.  The plerocercoids pass through several paratenic hosts before reaching a suitable definitive host where it can mature.  Once eaten by a canid or felid, the tapeworm matures and begins producing eggs.  Theoretically, a canid or felid that ate an infected human could become infected.

text: Spirometra is a

text: genus

text: of

text: Pseudophyllid

text: cestode

text: that reproduces in

text: canines

text: and

text: feline

text: s but which can cause pathology in humans.  As an adult, this

text: tapeworm

text: lives in the

text: small intestine

text: of its

text: definitive host

text: and produces eggs that pass with the animal's

text: feces

text: .  The eggs hatch into

text: coracidia

text: which are eaten by

text: copepod

text: s which become infected themselves.  In the copepod, the worm forms a

text: procercoid

text: , which is infective to

text: vertebrate

text: s that ingest them.  Often, because the copepods are so small, vertebrates ingest copepods accidentally by drinking them.  In the vertebrate, the worms enter the

text: plerocercoid

text: stage.  The plerocercoids pass through several

text: paratenic

text: hosts before reaching a suitable definitive host where it can mature.  Once eaten by a canid or felid, the tapeworm matures and begins producing eggs.  Theoretically, a canid or felid that ate an infected human could become infected.

text: Over the course of his career, Hall’s laboratory research has focused on developmental biology and evolutionary biology. His work played a major role in integrating these two fields into the discipline now known as Evolutionary Developmental Biology (evo-devo). He and his students, according to one source, “pioneered an epigenetic view of bone differentiation and of vertebrate development in general, and highlighted the importance of epigenetic tissue interactions in vertebrate evolution.” His 1975 paper “Evolutionary consequences of skeletal differentiation” (American Zoologist) marked the beginning of “the process of building a bridge between evolutionary and developmental biology from the developmental biology side.” His 1992 textbook Evolutionary Developmental Biology is widely viewed as definitive. “This work defines a field, which, in turn, has revitalized the study of evolution,” writes one source.

text: Sea levels in the Devonian were generally high. Marine faunas were dominated by bryozoa, diverse and abundant brachiopods, the enigmatic hederelloids, microconchids and corals. Lily-like crinoids were abundant, and trilobites were still fairly common. Among vertebrates, jawless armoured fish (ostracoderms) declined in diversity, while the jawed fish (gnathostomes) simultaneously increased in both the sea and fresh water. Armoured placoderms were numerous during the lower stages of the Devonian Period but became extinct in the Late Devonian, perhaps because of competition for food against the other fish species. Early cartilaginous (Chondrichthyes) and bony fishes (Osteichthyes) also become diverse and played a large role within the Devonian seas. The first abundant genus of shark,  Cladoselache, appeared in the oceans during the Devonian Period. The great diversity of fish around at the time have led to the Devonian being given the name "The Age of Fish" in popular culture.

text: Sea levels in the Devonian were generally high. Marine faunas were dominated by

text: bryozoa

text: , diverse and abundant

text: brachiopods

text: , the enigmatic

text: hederelloids

text: microconchids

text: and

text: coral

text: s. Lily-like

text: crinoids

text: were abundant, and

text: trilobite

text: s were still fairly common. Among vertebrates, jawless armoured fish (

text: ostracoderms

text: fresh water

text: . Armoured

text: placoderms

text: were numerous during the lower stages of the Devonian Period but became extinct in the Late Devonian, perhaps because of competition for food against the other fish species. Early cartilaginous (

text: Chondrichthyes

text: ) and bony fishes (

text: Osteichthyes

text: Cladoselache

text: , appeared in the oceans during the Devonian Period. The great diversity of fish around at the time have led to the Devonian being given the name "The Age of Fish" in popular culture.

text: Some fossil vertebrae have been found. The most notable example is a partially preserved vertebral column of a single specimen, excavated in the Antwerp basin, Belgium by M. Leriche in 1926. It comprises 150 vertebral centra, with the centra ranging from  to  in diameter. However, scientists have claimed that considerably larger vertebral centra can be expected. A partially preserved vertebral column of another C. megalodon specimen was excavated from Gram clay in Denmark by Bendix-Almgeen in 1983. This specimen comprises 20 vertebral centra, with the centra ranging from  to  in diameter.

text: Some fossil vertebrae have been found. The most notable example is a partially preserved vertebral column of a single specimen, excavated in the

text: Antwerp basin

text: Belgium

text: by M. Leriche in 1926. It comprises 150 vertebral

text: centra

text: , with the centra ranging from  to  in diameter. However, scientists have claimed that considerably larger vertebral centra can be expected. A partially preserved vertebral column of another C. megalodon specimen was excavated from Gram clay in

text: Denmark

text: by Bendix-Almgeen in 1983. This specimen comprises 20 vertebral centra, with the centra ranging from  to  in diameter.

text: Clodronic acid (INN) or clodronate disodium (USAN) is a first generation (non-nitrogenous) bisphosphonate. It is an anti-osteoporotic drug approved for the prevention and treatment of osteoporosis in post-menopausal women and men to reduce vertebral fractures, hyperparathyroidism, hypercalcemia in malignancy, multiple myeloma and fracture related pain because of its potent anti-inflammatory and analgesic effects shown as a reduction in inflammatory markers like IL-1β, IL-6, and TNF-alfa. While bisphosphonates are shown to be effective in reducing vertebral fractures and pain, their role in improving overall survival remains unclear.

text: Clodronic acid (

text: INN

text: ) or clodronate disodium (

text: USAN

text: ) is a first generation (non-nitrogenous)

text: bisphosphonate

text: . It is an anti-osteoporotic drug approved for the prevention and treatment of

text: osteoporosis

text: in post-menopausal women and men to reduce vertebral fractures,

text: hyperparathyroidism

text: hypercalcemia

text: in malignancy,

text: multiple myeloma

text: and fracture related pain because of its potent anti-inflammatory and analgesic effects shown as a reduction in inflammatory markers like

text: , and

text: TNF-alfa

text: . While bisphosphonates are shown to be effective in reducing vertebral fractures and pain, their role in improving overall survival remains unclear.

text: Like all Plasmodium species P. gonatodi has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. gonatodi has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: Another notable example of animals possessing pharyngeal jaws are the fish from the family Cichlidae. Cichlid pharyngeal jaws have become very specialized in prey processing and may have helped cichlid fishes become one of the most diverse families of vertebrates. However, later studies based on Lake Victoria cichlids suggest that this trait may also become a handicap when competing with other predator species.

text: Another notable example of animals possessing pharyngeal jaws are the fish from the family

text: Cichlid

text: ae. Cichlid pharyngeal jaws have become very specialized in prey processing and may have helped cichlid fishes become one of the most diverse families of vertebrates. However, later studies based on

text: Lake Victoria

text: cichlids suggest that this trait may also become a handicap when competing with other

text: predator

text: species.

text: Like all Plasmodium species P. saurocaudatum has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. saurocaudatum has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: The areas both in and surrounding the Rupununi river are home to a great diversity of terrestrial and aquatic ecosystems that harbor many species extirpated from other areas of South America. The Rupununi's freshwater eco-regions are areas of exceptional species richness, comparable to that of the Amazonia. Flora and fauna flourish in the Rupununi river because of the Rupununi's isolation from human activity. During an expedition, the South Rupununi Biodiversity Assessment Team (BAT), described the Rupununi river as being "very diverse"."The Northern Rupununi has more than fourteen hundred species of vertebrates, more than twenty-eight hundred species of plants, and countless species of invertebrates" (Rupununi, Rediscovering a Lost World).

text: This list of fossil fishes described in 2016 is a list of new taxa of jawless vertebrates, placoderms, acanthodians, fossil cartilaginous fishes, bony fishes and other fishes of every kind that have been described during the year 2016, as well as other significant discoveries and events related to paleontology of fishes that occurred in the year 2016. The list only includes taxa at the level of genus or species.

text: This list of

text: fossil

text: fishes

text: described in 2016 is a list of new

text: taxa

text: of

text: jawless vertebrates

text: placoderm

text: s,

text: acanthodians

text: , fossil

text: cartilaginous fishes

text: bony fishes

text: and other fishes of every kind that have been

text: described

text: during the year 2016, as well as other significant discoveries and events related to

text: paleontology

text: of fishes that occurred in the year 2016. The list only includes taxa at the level of

text: genus

text: or

text: species

text: The pigeye shark or Java shark (Carcharhinus amboinensis) is an uncommon species of requiem shark, in the family Carcharhinidae, found in the warm coastal waters of the eastern Atlantic and western Indo-Pacific. It prefers shallow, murky environments with soft bottoms, and tends to roam within a fairly localised area. With its bulky grey body, small eyes, and short, blunt snout, the pigeye shark looks almost identical to (and is often confused with) the better-known bull shark (C. leucas). The two species differ in vertebral count, the relative sizes of the dorsal fins, and other subtle traits. This shark typically reaches lengths of .

text: The pigeye shark or Java shark (Carcharhinus amboinensis) is an uncommon

text: species

text: of

text: requiem shark

text: , in the

text: family

text: Carcharhinidae, found in the warm coastal waters of the eastern Atlantic and western

text: Indo-Pacific

text: . It prefers shallow, murky environments with soft bottoms, and tends to roam within a fairly localised area. With its bulky grey body, small eyes, and short, blunt snout, the pigeye shark looks almost identical to (and is often confused with) the better-known

text: bull shark

text: (C. leucas). The two species differ in

text: vertebra

text: l count, the relative sizes of the

text: dorsal fin

text: s, and other subtle traits. This shark typically reaches lengths of .

text: Ray-finned fishes are the dominant vertebrate group, containing half of all known vertebrate species. They inhabit abyssal depths in the sea, coastal inlets and freshwater rivers and lakes, and are a major source of food for humans.

text: Over 32,000 species of fish have been described, making them the most diverse group of vertebrates. In addition, there are many species of shellfish. However, only a small number of species are commonly eaten by humans.

text: Over 32,000

text: species

text: of

text: fish

text: have been described, making them the most diverse group of vertebrates. In addition, there are many species of

text: shellfish

text: . However, only a small number of species are commonly eaten by humans.

text: The issue here is psychology versus social intelligence—as a separate and distinct perspective, seldom articulated. An appropriate introduction contains certain hypothetical assumptions about social structure and function, as it relates to intelligence defined and expressed by groups, constrained by cultural expectations that assert potential realities, but make no claims that there is an "exterior" social truth to be defined. This perspective pursues the view that social structures can be defined with the warning that what is mapped into the structure and how that information is stored, retrieved, and decided upon are variable, but can be contained in an abstract and formal grammar—a sort of game of definitions and rules that permit and project an evolving intelligence. Two halves of the coin: one half psychology; the other half social. Unfortunately, most references to social intelligence relate to an individual's social skills. Not mentioned, and more important, is how social intelligence (speaking of a group or assembly of groups) processes information about the world and shares it with participants in the group(s). Are there social structures or can they be designed to accumulate and reveal information to the individual or to other groups. The bigger question is how groups and societies map the environment (ecological, social and personal) into a social structure. How is that structure able to contain a worldview and to reveal that view to the participants? How are decisions made?

text: Vertebrates:

text: Vertebrates:

text: When the damage increases and the chondral defect reaches the subchondral bone, the blood supply in the bone starts a healing process in the defect. Scar tissue made up of a type of cartilage called fibrocartilage is then formed. Although fibrocartilage is able to fill in articular cartilage defects, its structure is significantly different from that of hyaline cartilage; it is much denser and it doesn't withstand the demands of everyday activities as much as hyaline cartilage. It is therefore at a higher risk of breaking down.

text: When the damage increases and the chondral defect reaches the

text: subchondral bone

text: , the blood supply in the bone starts a healing process in the defect. Scar tissue made up of a type of cartilage called

text: fibrocartilage

text: is then formed. Although fibrocartilage is able to fill in articular cartilage defects, its structure is significantly different from that of hyaline cartilage; it is much denser and it doesn't withstand the demands of everyday activities as much as hyaline cartilage. It is therefore at a higher risk of breaking down.

text: Bonaparte (1996) interpreted the relatively large orbital opening in the skull as a juvenile trait. Tykoski agreed (2005) and suggested that certain skull features of the type specimen suggested that it was young, specifically, the skull bones are not completely fused, relatively large orbits, and a short snout. Sereno et al. (1993), supported the notion that Eoraptor was an adult specimen based on the closure of sutures in the vertebral column, and the partial fusion of the scapulocoracoid.

text: Testosterone is observed in most vertebrates. Testosterone and the classical nuclear androgen receptor first appeared in gnathostomes (jawed vertebrates). Agnathans (jawless vertebrates) such as lampreys don't produce testosterone but instead use 4-androstenedione as a male sex hormone. Fish make a slightly different form called 11-ketotestosterone. Its counterpart in insects is ecdysone. The presence of these ubiquitous steroids in a wide range of animals suggest that sex hormones have an ancient evolutionary history.

text: Testosterone is observed in most vertebrates. Testosterone and the classical nuclear

text: androgen receptor

text: first appeared in

text: gnathostome

text: s (jawed vertebrates).

text: Agnathan

text: s (jawless vertebrates) such as

text: lamprey

text: s don't produce testosterone but instead use

text: as a male sex hormone.

text: Fish

text: make a slightly different form called

text: . Its counterpart in insects is

text: ecdysone

text: . The presence of these ubiquitous steroids in a wide range of animals suggest that

text: sex hormone

text: s have an ancient evolutionary history.

text: Hyaline cartilage caps the long bones and the spinal vertebrae. Most childhood limb growth takes place at the ends of the long bones, not in the shaft. Normally, as a child grows, the most interior portion of the joint cartilage converts into bone, and new cartilage forms on the surface to maintain smooth joints. The old joint margins (edges) reabsorb, so that the overall shape of the joint is maintained as growth continues. Failure of this process throughout the body results in skeletal dysplasia. It also leads to very early onset of osteoarthritis, because the defective cartilage is extremely fragile and vulnerable to normal wear and tear.

text: Hyaline cartilage caps the long

text: bone

text: s and the spinal vertebrae. Most childhood limb growth takes place at the ends of the long bones, not in the shaft. Normally, as a child grows, the most interior portion of the joint cartilage converts into bone, and new cartilage forms on the surface to maintain smooth joints. The old joint margins (edges) reabsorb, so that the overall shape of the joint is maintained as growth continues. Failure of this process throughout the body results in skeletal dysplasia. It also leads to very early onset of

text: osteoarthritis

text: , because the defective cartilage is extremely fragile and vulnerable to normal wear and tear.

text: As the sclerotome develops, it condenses further eventually developing into the vertebral body. Development of the appropriate shapes of the vertebral bodies is regulated by HOX genes.

text: As the sclerotome develops, it condenses further eventually developing into the

text: vertebral body

text: . Development of the appropriate shapes of the vertebral bodies is regulated by

text: HOX gene

text: s.

text: Role of skin in locomotion  describes how the integumentary system is involved in locomotion. Typically the integumentary system can be thought of as skin, however the integumentary system also includes the segmented exoskeleton in arthropods and feathers of birds. The primary role of the integumentary system is to provide protection for the body. However, the structure of the skin has evolved to aid animals in their different modes of locomotion.Soft bodied animals such as starfish rely on the arrangement of the fibers in their tube feet for movement. Eels, snakes, and fish use their skin like an external tendon to generate the propulsive forces need for undulatory locomotion. Vertebrates that fly, glide, and parachute also have a characteristic fiber arrangements of their flight membranes that allows for the skin to maintain its structural integrity during the stress and strain experienced during flight.

text: Role of skin in locomotion  describes how the

text: integumentary system

text: is involved in locomotion. Typically the integumentary system can be thought of as

text: skin

text: , however the integumentary system also includes the

text: segmented exoskeleton

text: in

text: arthropod

text: s and

text: feathers

text: of birds. The primary role of the

text: integumentary system

text: is to provide protection for the body. However, the structure of the skin has evolved to aid animals in their different modes of locomotion.Soft bodied

text: animals

text: such as

text: starfish

text: rely on the arrangement of the fibers in their tube feet for movement.

text: Eels

text: snakes

text: , and

text: fish

text: use their skin like an external

text: tendon

text: to generate the propulsive forces need for

text: undulatory locomotion

text: . Vertebrates that fly, glide, and parachute also have a characteristic

text: fiber

text: arrangements of their flight

text: membrane

text: s that allows for the skin to maintain its structural integrity during the stress and strain experienced during flight.

text: Additional support comes from work on the development of the polychaete annelid Platynereis dumerilii, another protostome. Even more so than Drosophila, its pattern of central-nervous-system development is strikingly similar to that of vertebrates, but inverted. There is also evidence from left-right asymmetry. Vertebrates have a highly conserved Nodal signaling pathway that acts on the left side of the body, determining left-right asymmetries of internal organs. Sea urchins have the same signaling pathway, but it acts on the right side of the body. It was even shown that an opposing right-sided signal for regulating left-right asymmetry in vertebrates, i.e. BMP signaling pathway, is activated on the left side of the sea urchin larva, suggesting an axial inversion during evolution from basal deuterostome to chordate such like amphioxus. Because in amphioxus, Nodal signaling pathway is on the left side of the embryo, which is the same situation as vertebrates.  Sea urchins, like other echinoderms, have radially-symmetric adults, but bilaterally-symmetric larvae. Since sea urchins are deuterostomes, this suggests that the ancestral deuterostome shared its orientation with protostomes, and that dorsoventral inversion originated in some ancestral chordate.

text: Additional support comes from work on the development of the

text: polychaete

text: annelid

text: Platynereis dumerilii

text: , another protostome. Even more so than Drosophila, its pattern of central-nervous-system development is strikingly similar to that of vertebrates, but inverted. There is also evidence from left-right asymmetry. Vertebrates have a highly conserved Nodal signaling pathway that acts on the left side of the body, determining left-right asymmetries of internal organs.

text: Sea urchin

text: s have the same signaling pathway, but it acts on the right side of the body. It was even shown that an opposing right-sided signal for regulating left-right asymmetry in vertebrates, i.e. BMP signaling pathway, is activated on the left side of the sea urchin larva, suggesting an axial inversion during evolution from basal deuterostome to chordate such like amphioxus. Because in amphioxus, Nodal signaling pathway is on the left side of the embryo, which is the same situation as vertebrates.  Sea urchins, like other echinoderms, have radially-symmetric adults, but bilaterally-symmetric larvae. Since sea urchins are deuterostomes, this suggests that the ancestral deuterostome shared its orientation with protostomes, and that dorsoventral inversion originated in some ancestral chordate.

text: The defining characteristic of a vertebrate is the vertebral column, in which the notochord (a stiff rod of uniform composition) found in all chordates has been replaced by a segmented series of stiffer elements (vertebrae) separated by mobile joints (intervertebral discs, derived embryonically and evolutionarily from the notochord). However, a few fish have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon.

text: vertebral column

text: , in which the

text: notochord

text: chordates

text: has been replaced by a segmented series of stiffer elements (vertebrae) separated by mobile joints (intervertebral discs, derived embryonically and evolutionarily from the notochord). However, a few fish have secondarily lost this anatomy, retaining the notochord into adulthood, such as the

text: sturgeon

text: When vertebrates found their way onto land, the hyomandibula, with its location near the ear, began to function as a sound amplifier beside its function to support the skull. As evolution later attached the cranium of terrestrial vertebrates to the rest of the skull, the hyomandibula lost its supportive function and became an interior organ, the stapes, and thus its secondary function had become its primary function.

text: When vertebrates found their way onto land, the hyomandibula, with its location near the ear, began to function as a sound amplifier beside its function to support the skull. As evolution later attached the cranium of terrestrial vertebrates to the rest of the skull, the hyomandibula lost its supportive function and became an interior organ, the

text: stapes

text: , and thus its secondary function had become its primary function.

text: The external oblique functions to pull the chest downwards and compress the abdominal cavity, which increases the intra-abdominal pressure as in a valsalva maneuver.  It also has limited actions in both flexion and rotation of the vertebral column. One side of the obliques contracting can create lateral flexion.

text: The external oblique functions to pull the chest downwards and compress the abdominal cavity, which increases the intra-abdominal pressure as in a

text: valsalva maneuver

text: .  It also has limited actions in both flexion and rotation of the

text: vertebral column

text: . One side of the obliques contracting can create lateral flexion.

text: Kabardino-Balkarski is located in the Caucasus mixed forests ecoregion.  This ecoregion is located along the Caucasus Mountains between the Black Sea and the Caspian Sea.  It has one of the highest levels of species endemism and diversity in the world: 23% of vascular species, and 10% of vertebrates.

text: Kabardino-Balkarski is located in the Caucasus mixed forests ecoregion.  This ecoregion is located along the Caucasus Mountains between the

text: Black Sea

text: and the

text: Caspian Sea

text: .  It has one of the highest levels of species endemism and diversity in the world: 23% of vascular species, and 10% of vertebrates.

text: :This article is about a group of ray-finned fish called Acanthomorpha or acanthomorphs.  ‘’Acanthomorph’‘ is also a descriptive name for a spiny-walled subgroup of the microscopic fossils called acritarchs.Acanthomorpha (meaning "thorn-shaped" in Greek) is a extraordinarily diverse taxon of teleost fishes with spiny-rays. The clade contains about one third of the world’s modern species of vertebrates: over 14,000 species.

text: :This article is about a group of ray-finned fish called Acanthomorpha or acanthomorphs.  ‘’Acanthomorph’‘ is also a descriptive name for a spiny-walled subgroup of the microscopic fossils called

text: acritarch

text: s.Acanthomorpha (meaning "thorn-shaped" in Greek) is a extraordinarily diverse

text: taxon

text: of

text: teleost

text: fishes with spiny-

text: ray

text: s. The

text: clade

text: contains about one third of the world’s modern species of vertebrates: over 14,000 species.

text: Traumatic vertebral dissection may follow blunt trauma to the neck, such as in a traffic collision, direct blow to the neck, strangulation, or whiplash injury. 1–2% of those with major trauma may have an injury to the carotid or vertebral arteries. In many cases of vertebral dissection, people report recent very mild trauma to the neck or sudden neck movements, e.g. in the context of playing sports. Others report a recent infection, particularly respiratory tract infections associated with coughing. Trauma has been reported to have occurred within a month of dissection in 40% with nearly 90% of this time the trauma being minor.  It has been difficult to prove the association with mild trauma and infections statistically. It is likely that many "spontaneous" cases may in fact have been caused by such relatively minor insults in someone predisposed by other structural problems to the vessels.

text: Traumatic vertebral dissection may follow blunt trauma to the neck, such as in a

text: traffic collision

text: , direct blow to the neck,

text: strangulation

text: , or

text: whiplash injury

text: . 1–2% of those with major trauma may have an injury to the carotid or vertebral arteries. In many cases of vertebral dissection, people report recent very mild trauma to the neck or sudden neck movements, e.g. in the context of playing sports. Others report a recent infection, particularly

text: respiratory tract infection

text: s associated with

text: cough

text: ing. Trauma has been reported to have occurred within a month of dissection in 40% with nearly 90% of this time the trauma being minor.  It has been difficult to prove the association with mild trauma and infections statistically. It is likely that many "spontaneous" cases may in fact have been caused by such relatively minor insults in someone predisposed by other structural problems to the vessels.

text: The describing authors established some distinguishing traits. These were all autapomorphies, unique derived qualities. The longest neural spines reach a height of at least 4.3 times the height of their vertebral bodies. The rear middle back vertebrae have a very high and deep depression between their rear articular processes and the base of the neural spine, 2.6 times higher than that base is long, measured from the front to the rear. The rib of the dorsosacral vertebra is fused with the sacral yoke. With the second and third sacral vertebrae the keel at the underside is limited to the front part of the vertebral body. With the fourth sacral vertebra the keel has a similar position but is low and wide. The facets for the dorsosacral and first sacral ribs are located close to each other near the top edge of the ilium, higher than the facets of the other sacral ribs. The ridge on the inner side of the rear blade of the ilium runs obliquely to behind and above, forming a slightly swollen bone shelf, directed to the inside, on the rear part of the rear blade. The lower end of the ischium has a D-shaped cross-section due to an extension on the outer side.

text: The describing authors established some distinguishing traits. These were all

text: autapomorphies

text: , unique derived qualities. The longest neural spines reach a height of at least 4.3 times the height of their vertebral bodies. The rear middle back vertebrae have a very high and deep depression between their rear articular processes and the base of the neural spine, 2.6 times higher than that base is long, measured from the front to the rear. The rib of the dorsosacral vertebra is fused with the sacral yoke. With the second and third sacral vertebrae the keel at the underside is limited to the front part of the vertebral body. With the fourth sacral vertebra the keel has a similar position but is low and wide. The facets for the dorsosacral and first sacral ribs are located close to each other near the top edge of the ilium, higher than the facets of the other sacral ribs. The ridge on the inner side of the rear blade of the ilium runs obliquely to behind and above, forming a slightly swollen bone shelf, directed to the inside, on the rear part of the rear blade. The lower end of the ischium has a D-shaped cross-section due to an extension on the outer side.

text: Several characteristics in therapsids have been noted as being consistent with the development of endothermy: the presence of turbinates, erect limbs, highly vascularized bones, limb and tail proportions conducive to the preservation of body heat, and the absence of growth rings in bones. Therefore, like modern mammals, non-mammalian therapsids were most likely warm-blooded.

text: Several characteristics in therapsids have been noted as being consistent with the development of

text: endothermy

text: : the presence of

text: turbinates

text: , erect limbs, highly

text: vascularized bones

text: , limb and tail proportions conducive to the preservation of body heat, and the absence of

text: growth ring

text: s in bones. Therefore, like modern mammals, non-mammalian therapsids were most likely warm-blooded.

text: Cartilage in the second pharyngeal arch is referred to as Reichert's cartilage and contributes to many structures in the fully developed adult. In contrast to the Meckel's cartilage of the first pharyngeal arch it does not constitute a continuous element, and instead is composed of two distinct cartilagenous segments joined by a faint layer of mesenchyme.  Dorsal ends of Reichert's cartilage ossify during development to form the stapes of the middle ear before being incorporated into the middle ear cavity, while the ventral portion ossifies to form the lesser cornu and upper part of the body of the hyoid bone. Caudal to what will eventually become the stapes, Reichert's cartilage also forms the styloid process of the temporal bone. The cartilage between the hyoid bone and styloid process will not remain as development continues, but its perichondrium will eventually form the stylohyoid ligament.

text: Cartilage in the second pharyngeal arch is referred to as Reichert's cartilage and contributes to many structures in the fully developed adult. In contrast to the

text: Meckel's cartilage

text: of the

text: first pharyngeal arch

text: it does not constitute a continuous element, and instead is composed of two distinct cartilagenous segments joined by a faint layer of

text: mesenchyme

text: .  Dorsal ends of Reichert's cartilage

text: ossify

text: during development to form the

text: stapes

text: of the

text: middle ear

text: before being incorporated into the middle ear cavity, while the ventral portion ossifies to form the lesser cornu and upper part of the body of the

text: hyoid bone

text: . Caudal to what will eventually become the

text: stapes

text: , Reichert's cartilage also forms the

text: styloid process

text: of the

text: temporal bone

text: . The cartilage between the

text: hyoid bone

text: and

text: styloid process

text: will not remain as development continues, but its

text: perichondrium

text: will eventually form the

text: stylohyoid ligament

text: In the adjacent picture, the arrow points to an inferior costal facet. The facets are named for their location on the vertebral body, not the rib. The inferior costal facet is located on the inferior aspect of the vertebral body, but has a superior location on the rib. Similarly, the superior costal facet is superior on the vertebral body but is inferior on the rib.

text: Cartilaginous fish, such as sharks, also lack a true maxilla. Their upper jaw is instead formed from a cartilagenous bar that is not homologous with the bone found in other vertebrates.

text: Cartilaginous fish

text: , such as sharks, also lack a true maxilla. Their upper jaw is instead formed from a

text: cartilage

text: nous bar that is not

text: homologous

text: Vertebral anomalies, or defects of the spinal column, usually consist of small (hypoplastic) vertebrae or hemivertebra where only one half of the bone is formed. About 80 percent of patients with VACTERL association will have vertebral anomalies. In early life these rarely cause any difficulties, although the presence of these defects on a chest x-ray may alert the physician to other defects associated with VACTERL. Later in life these spinal column abnormalities may put the child at risk for developing scoliosis, or curvature of the spine.

text: Vertebral anomalies, or defects of the spinal column, usually consist of small (

text: hypoplastic

text: ) vertebrae or hemivertebra where only one half of the bone is formed. About 80 percent of patients with VACTERL association will have vertebral anomalies. In early life these rarely cause any difficulties, although the presence of these defects on a chest x-ray may alert the physician to other defects associated with VACTERL. Later in life these spinal column abnormalities may put the child at risk for developing

text: scoliosis

text: , or curvature of the spine.

text: Conventional classification has living vertebrates grouped into seven classes based on traditional interpretations of gross anatomical and physiological traits. This classification is the one most commonly encountered in school textbooks, overviews, non-specialist, and popular works. The extant vertebrates are:

text: Conventional classification has living vertebrates grouped into seven classes based on traditional interpretations of gross

text: anatomical

text: and

text: physiological

text: traits. This classification is the one most commonly encountered in school textbooks, overviews, non-specialist, and popular works. The

text: extant

text: vertebrates are:

text: In the Early Devonian (416-397 Ma), the lobe-finned fishes split into two main lineages — the coelacanths and the rhipidistians. The former never left the oceans and their heyday was the Late Devonian and Carboniferous, from 385 to 299 Ma, as they were more common during those periods than in any other period in the Phanerozoic; coelacanths still live today in the oceans (genus Latimeria). The Rhipidistians, whose ancestors probably lived in estuaries, migrated into freshwater habitats. They in turn split into two major groups: the lungfish and the tetrapodomorphs. The lungfish's greatest diversity was in the Triassic period; today there are fewer than a dozen genera left. The lungfish evolved the first proto-lungs and proto-limbs; developing the ability to live outside a water environment in the middle Devonian (397-385 Ma). The first tetrapodomorphs, which included the gigantic rhizodonts, had the same general anatomy as the lungfish, who were their closest kin, but they appear not to have left their water habitat until the late Devonian epoch (385 - 359 Ma), with the appearance of tetrapods (four-legged vertebrates). Tetrapods are the only tetrapodomorphs that survived after the Devonian. Lobe-finned fishes continued until towards the end of Paleozoic era, suffering heavy losses during the Permian-Triassic extinction event (251 Ma).

text: In the Early Devonian (416-397 Ma), the lobe-finned fishes split into two main lineages — the

text: coelacanth

text: s and the

text: rhipidistian

text: s. The former never left the oceans and their heyday was the

text: Late Devonian

text: and

text: Carboniferous

text: , from 385 to 299 Ma, as they were more common during those periods than in any other period in the Phanerozoic; coelacanths still live today in the

text: ocean

text: s (genus

text: Latimeria

text: ). The Rhipidistians, whose ancestors probably lived in

text: estuaries

text: , migrated into freshwater habitats. They in turn split into two major groups: the

text: lungfish

text: and the

text: tetrapodomorph

text: s. The lungfish's greatest diversity was in the

text: Triassic

text: period; today there are fewer than a dozen genera left. The lungfish evolved the first proto-lungs and proto-limbs; developing the ability to live outside a water environment in the middle Devonian (397-385 Ma). The first tetrapodomorphs, which included the gigantic rhizodonts, had the same general anatomy as the lungfish, who were their closest kin, but they appear not to have left their water habitat until the late Devonian epoch (385 - 359 Ma), with the appearance of

text: tetrapods

text: (four-legged vertebrates). Tetrapods are the only tetrapodomorphs that survived after the Devonian. Lobe-finned fishes continued until towards the end of Paleozoic era, suffering heavy losses during the

text: Permian-Triassic extinction event

text: (251 Ma).

text: Endochondral ossification is responsible for the initial bone development from cartilage in utero and infants and the longitudinal growth of long bones in the epiphyseal plate. The plate's chondrocytes are under constant division by mitosis. These daughter cells stack facing the epiphysis while the older cells are pushed towards the diaphysis. As the older chondrocytes degenerate, osteoblasts ossify the remains to form new bone. In puberty increasing levels of estrogen, in both females and males, leads to increased apoptosis of chondrocytes in the epiphyseal plate. Depletion of chondrocytes due to apoptosis leads to less ossification and growth slows down and later stops when the entire cartilage have become replaced by bone, leaving only a thin epiphyseal scar which later disappears.

text: Endochondral ossification

text: is responsible for the initial bone development from cartilage

text: in utero

text: and infants and the longitudinal growth of long bones in the epiphyseal plate. The plate's

text: chondrocytes

text: are under constant division by

text: mitosis

text: . These

text: daughter cell

text: s stack facing the

text: epiphysis

text: while the older cells are pushed towards the

text: diaphysis

text: . As the older chondrocytes degenerate,

text: osteoblasts

text: ossify the remains to form new bone. In puberty increasing levels of estrogen, in both females and males, leads to increased

text: apoptosis

text: of chondrocytes in the epiphyseal plate. Depletion of chondrocytes due to apoptosis leads to less

text: ossification

text: and growth slows down and later stops when the entire cartilage have become replaced by bone, leaving only a thin epiphyseal scar which later disappears.

text: It has been suggested that invertebrate and vertebrate signaling downstream from Smoothened has diverged significantly. The role of Suppressor of Fused (SUFU) has been enhanced in vertebrates compared to Drosophila where its role is relatively minor. Costal-2 is particularly important in Drosophila. The protein kinase Fused is a regulator of SUFU in Drosophila, but may not play a role in the Hh pathway of vertebrates. In vertebrates, Hh signaling has been heavily coupled to cilia.

text: It has been suggested that invertebrate and vertebrate signaling downstream from Smoothened has diverged significantly. The role of Suppressor of Fused (SUFU) has been enhanced in vertebrates compared to Drosophila where its role is relatively minor. Costal-2 is particularly important in Drosophila. The protein kinase Fused is a regulator of SUFU in Drosophila, but may not play a role in the Hh pathway of vertebrates. In vertebrates, Hh signaling has been heavily coupled to

text: cilia

text: Castile and León has a great diversity of fauna. Some of these are notable either for being endemic to the region or for their rarity. 418 species of vertebrates have been identified, constituting 63 percent of the vertebrates that can be found in Spain. Animals adapted to the high mountains, inhabitant of rocky landscapes, river dwellers, lowland species, and forest animals all can be found in Castile and León.

text: Castile and León has a great diversity of fauna. Some of these are notable either for being endemic to the region or for their rarity. 418 species of

text: vertebrate

text: s have been identified, constituting 63 percent of the vertebrates that can be found in Spain. Animals adapted to the high mountains, inhabitant of rocky landscapes, river dwellers, lowland species, and forest animals all can be found in Castile and León.

text: They are minute rounded or pyriform parasites found within erythrocytes, or other circulating or endothelial cells of vertebrates, where they reproduce by merogony. The trophozoite stage is separated from erythrocyte by a single membrane. This distinguishes them from other blood parasites that usually have at least two membranes.

text: They are minute rounded or

text: pyriform

text: parasites found within erythrocytes, or other circulating or endothelial cells of vertebrates, where they reproduce by

text: merogony

text: . The

text: trophozoite

text: stage is separated from erythrocyte by a single membrane. This distinguishes them from other blood parasites that usually have at least two membranes.

text: The style of writing is very light and readable, and technical concepts kept to a minimum. In the book vertebrate evolution is studied utilizing comparative anatomy & functional morphology of existing vertebrates, and fossil records. The book is considered a classic and has been used very frequently as a college-level or university introductory level text on the subjects of basic paleontology and vertebrate evolution.

text: The style of writing is very light and readable, and technical concepts kept to a minimum. In the book vertebrate evolution is studied utilizing comparative anatomy & functional morphology of existing vertebrates, and fossil records. The book is considered a classic and has been used very frequently as a college-level or university introductory level text on the subjects of basic

text: paleontology

text: and

text: vertebrate evolution

text: Three critical assumptions underlie the study of Mhc evolution: First, the Mhc is absent in all non-vertebrates. Second, jawless vertebrates (Agnatha) are monophyletic and are a sister group of jawed vertebrates (Gnathostoma). And third, jawless vertebrates lack the Mhc, which is present in all the jawed vertebrates. Klein’s group contributed significantly to the current general acceptance of these suppositions. The absence of the Mhc in non-vertebrates became apparent when scrutiny of non-vertebrate genomes failed to identify homologs of Mhc genes. Klein’s group provided strong support for agnathan monophyly by cloning, sequencing, and analyzing long DNA stretches of the representative agnathan and gnathostome species. And they isolated, in collaboration with Max Cooper’s group, lymphocyte-like cells, cloned, sequenced, and analyzed genes expressed in these cells, and found no evidence for expressed Mhc gene homologs. They did find, however, evidence for gradual evolution of the adaptive immune system. They could demonstrate the presence in jawless vertebrates of several auxiliary components and pathways, which the AIS co-opted when the three central receptors (Mhc, Tcr, and Bcr) emerged in the jawed vertebrates. They also contributed evidence for the omnipresence of Mhc genes in jawed vertebrates by identifying such genes in a wide range of species from bony fishes [zebrafish (Danio rerio), cichlid Aulonocara hansbaenschi, tilapia (Oreochromis niloticus), carp (Cyprinus carpio), guppy (Poecilia reticulata), threespine stickleback (Gasterosteus aculeatus), swordtail (Xiphophorus)]; through coelacanth (Latimeria chalumnae), African lungfish (Protopterus aethiopicus); birds [Bengalese finch (Lonchura striata), Darwin’s finches and their South American relatives]; to metatherian mammals [red-necked wallaby (Macropus rufogriseus) and eutherian mammal [rodents such as the mole rat (Spalax ehrenbergi)] and a variety of primates including prosimians, New World monkeys (NWM, Platyrrhini), Old World monkeys (OWM, Catarrhini) and apes]. In several of these species they worked out also the organization of the Mhcs, most notably in the zebrafish.

text: The classification of hagfish has been controversial. The issue is whether the hagfish is a degenerate type of vertebrate-fish (most closely related to lampreys), or represents a stage that precedes the evolution of the vertebral column (as do lancelets). The original scheme groups hagfish and lampreys together as cyclostomes (or historically, Agnatha), as the oldest surviving class of vertebrates alongside gnathostomes (the now-ubiquitous jawed vertebrates). An alternative scheme proposed that jawed vertebrates are more closely related to lampreys than to hagfish (i.e., that vertebrates include lampreys but exclude hagfish), and introduces the category craniata to group vertebrates near hagfish. Recent DNA evidence has supported the original scheme.

text: The classification of hagfish has been controversial. The issue is whether the hagfish is a degenerate type of vertebrate-fish (most closely related to lampreys), or represents a stage that precedes the evolution of the vertebral column (as do

text: lancelets

text: ). The original scheme groups hagfish and lampreys together as

text: cyclostomes

text: (or historically,

text: Agnatha

text: ), as the oldest surviving class of

text: vertebrates

text: alongside

text: gnathostomes

text: (the now-ubiquitous jawed vertebrates). An alternative scheme proposed that jawed vertebrates are more closely related to lampreys than to hagfish (i.e., that vertebrates include lampreys but exclude hagfish), and introduces the category

text: craniata

text: to group vertebrates near hagfish. Recent DNA evidence has supported the original scheme.

text: Pinealocytes in many non-mammalian vertebrates have a strong resemblance to the photoreceptor cells of the eye. Some evolutionary biologists believe that the vertebrate pineal cells possess a common evolutionary ancestor with retinal cells.

text: Pinealocyte

text: s in many non-mammalian

text: vertebrate

text: s have a strong resemblance to the

text: photoreceptor cell

text: s of the

text: eye

text: . Some evolutionary biologists believe that the vertebrate pineal cells possess a common

text: evolution

text: ary ancestor with retinal cells.

text: Calcaneal fracture- Camurati–Engelmann disease- Cancellous bone- Cartilage- Cartilaginous joint- Catel–Manzke syndrome- Cenani–Lenz syndactylism- Cervical dislocation- Cervical fracture- Cervical rib- Chalkstick fracture- Chance fracture- Chandler's disease- Charnley prosthesis- Charnley Retractor- Chauffeur's fracture- Child bone fracture- Chondroblast- Chondroblastoma- Chondrocyte- Chondrogenesis- Chondromalacia patellae- Chondromyxoid fibroma- Chondrosarcoma- Chopart's fracture-dislocation- Clarke's test- Clavicle fracture- Clay-shoveler fracture- Cleidocranial dysostosis- Clinodactyly- Club foot- Clubbed thumb- Cobb angle- Codman triangle- Cole carpenter syndrome- Colles' fracture- Combined tibia and fibula fracture- Compartment syndrome- Complex regional pain syndrome- Compression fracture- Computer-assisted orthopedic surgery- Congenital knee dislocation- Congenital limb deformities- Congenital patellar dislocation- Conradi–Hünermann syndrome- Coopernail's sign- Cortical bone- Cotrel–Dubousset instrumentation- Coxa valga- Coxa vara- Cozen's test- Crus fracture- Crush injury- Crush syndrome- Cubitus valgus- Cubitus varus- Cunningham shoulder reduction- Currarino syndrome

text: Calcaneal fracture

text: Camurati–Engelmann disease

text: Cancellous bone

text: Cartilage

text: Cartilaginous joint

text: Catel–Manzke syndrome

text: Cenani–Lenz syndactylism

text: Cervical dislocation

text: Cervical fracture

text: Cervical rib

text: Chalkstick fracture

text: Chance fracture

text: Chandler's disease

text: Charnley prosthesis

text: Charnley Retractor

text: Chauffeur's fracture

text: Child bone fracture

text: Chondroblast

text: Chondroblastoma

text: Chondrocyte

text: Chondrogenesis

text: Chondromalacia patellae

text: Chondromyxoid fibroma

text: Chondrosarcoma

text: Chopart's fracture-dislocation

text: Clarke's test

text: Clavicle fracture

text: Clay-shoveler fracture

text: Cleidocranial dysostosis

text: Clinodactyly

text: Club foot

text: Clubbed thumb

text: Cobb angle

text: Codman triangle

text: Cole carpenter syndrome

text: Colles' fracture

text: Combined tibia and fibula fracture

text: Compartment syndrome

text: Complex regional pain syndrome

text: Compression fracture

text: Computer-assisted orthopedic surgery

text: Congenital knee dislocation

text: Congenital limb deformities

text: Congenital patellar dislocation

text: Conradi–Hünermann syndrome

text: Coopernail's sign

text: Cortical bone

text: Cotrel–Dubousset instrumentation

text: Coxa valga

text: Coxa vara

text: Cozen's test

text: Crus fracture

text: Crush injury

text: Crush syndrome

text: Cubitus valgus

text: Cubitus varus

text: Cunningham shoulder reduction

text: Currarino syndrome

text: The vertebral arch is formed by pedicles and laminae. Two pedicles extend from the sides of the vertebral body to join the body to the arch. The pedicles are short thick processes that extend, one from each side, posteriorly, from the junctions of the posteriolateral surfaces of the centrum, on its upper surface.From each pedicle a broad plate, a lamina, projects backwards and medialwards to join and complete the vertebral arch and form the posterior border of the vertebral foramen, which completes the triangle of the vertebral foramen. The upper surfaces of the laminae are rough to give attachment to the ligamenta flava. These ligaments connect the laminae of adjacent vertebra along the length of the spine from the level of the second cervical vertebra. Above and below the pedicles are shallow depressions called vertebral notches (superior and inferior). When the vertebrae articulate the notches align with those on adjacent vertebrae and these form the openings of the intervertebral foramina. The foramina allow the entry and exit of the spinal nerves from each vertebra, together with associated blood vessels. The articulating vertebrae provide a strong pillar of support for the body.

text: The vertebral arch is formed by pedicles and laminae. Two pedicles extend from the sides of the vertebral body to join the body to the arch. The pedicles are short thick

text: process

text: es that extend, one from each side, posteriorly, from the junctions of the posteriolateral surfaces of the centrum, on its upper surface.From each pedicle a broad plate, a lamina, projects backwards and medialwards to join and complete the vertebral arch and form the posterior border of the vertebral foramen, which completes the triangle of the vertebral foramen. The upper surfaces of the laminae are rough to give attachment to the

text: ligamenta flava

text: . These ligaments connect the laminae of adjacent vertebra along the length of the spine from the level of the second cervical vertebra. Above and below the pedicles are shallow depressions called vertebral notches (superior and inferior). When the vertebrae

text: articulate

text: the notches align with those on adjacent vertebrae and these form the openings of the

text: intervertebral foramina

text: . The foramina allow the entry and exit of the spinal nerves from each vertebra, together with associated blood vessels. The articulating vertebrae provide a strong pillar of support for the body.

text: The molecular mechanism behind this process lies in the expression and repression of bone morphogenetic proteins (BMPs). BMPs are a wide family of proteins that perform many functions throughout the growing embryo, including stimulating the growth of cartilage and bone. In order to allow for the growth of precursor neural tissues, as opposed to precursor bone or cartilage tissues, BMP expression is decreased in the neural plate, specifically along the medial line, where the neural groove will soon form.The proteins produced from the genes Noggin and Chordin inhibit these BMPs, and subsequently allow neural commitment genes, like SOX, to be expressed.  These genes encode transcription factors, which alter the genomic expression of these cells, furthering them along the path of neural cell commitment.This process of BMP inhibition allows for the anchoring of the medial hinge point cells, providing the  neural folds with the foundation necessary for folding and closure to occur.  Noggin and Chordin have other roles in the neurulation process, including stimulating the neural crest cells to emigrate from the newly formed neural tube. The Sonic hedgehog gene also plays a role in attenuating BMP expression, forming the medial hinge point while inhibiting the formation of the dorsolateral hinge points, and in ensuring the proper closure of the neural folds.<ref>{{cite journal  |vauthors=Kirillova I, Novikova I, Augé J, etal |title=Expression of the sonic hedgehog gene in human embryos with neural tube defects |journal=Teratology |volume=61 |issue=5 |pages=347–54 |date=May 2000  |pmid=10777830 |doi=10.1002/(SICI)1096-9926(200005)61:5

text: The molecular mechanism behind this process lies in the expression and repression of

text: bone morphogenetic proteins

text: (BMPs). BMPs are a wide family of proteins that perform many functions throughout the growing embryo, including stimulating the growth of cartilage and bone. In order to allow for the growth of precursor neural tissues, as opposed to precursor bone or cartilage tissues, BMP expression is decreased in the neural plate, specifically along the medial line, where the neural groove will soon form.The proteins produced from the

text: gene

text: s

text: Noggin

text: and

text: Chordin

text: inhibit these BMPs, and subsequently allow neural commitment genes, like

text: SOX

text: , to be expressed.  These genes encode

text: transcription factor

text: s, which alter the genomic expression of these cells, furthering them along the path of neural cell commitment.This process of BMP inhibition allows for the anchoring of the medial hinge point cells, providing the  neural folds with the foundation necessary for folding and closure to occur.  Noggin and Chordin have other roles in the neurulation process, including stimulating the neural crest cells to emigrate from the newly formed neural tube. The

text: Sonic hedgehog

text: gene also plays a role in attenuating BMP expression, forming the medial hinge point while inhibiting the formation of the dorsolateral hinge points, and in ensuring the proper closure of the neural folds.<ref>{{cite journal  |vauthors=Kirillova I, Novikova I, Augé J, etal |title=Expression of the sonic hedgehog gene in human embryos with neural tube defects |journal=Teratology |volume=61 |issue=5 |pages=347–54 |date=May 2000  |pmid=10777830 |doi=10.1002/(SICI)1096-9926(200005)61:5

text: David Burton Wake (born June 8, 1936, Webster, South Dakota) is emeritus professor of integrative biology and former Director and curator of herpetology of the Museum of Vertebrate Zoology at the University of California, Berkeley. Wake is known for his work on the biology and evolution of salamanders as well as general issues of vertebrate evolutionary biology. He has served as president of the Society for the Study of Evolution, the American Society of Naturalists, and American Society of Zoologists.  He is a member of the American Association for the Advancement of Science, the Linnean Society of London, the American Academy of Arts and Sciences, the American Philosophical Society, and in 1998 was elected into the National Academy of Sciences. He was awarded the 2006 Leidy Award from the Academy of Natural Sciences of Philadelphia. He is married to the biologist Marvalee Wake. Wake is commemorated in the names of the salamander Cryptotriton wakei (Wake's moss salamander), the skink genus Davewakeum, the frog genus Wakea, and the lizard Cyrtodactylus wakeorum (Wakes' gecko)—the latter two named jointly after him and his wife.

text: David Burton Wake (born June 8, 1936,

text: Webster, South Dakota

text: ) is emeritus professor of

text: integrative biology

text: and former Director and curator of

text: herpetology

text: of the

text: Museum of Vertebrate Zoology

text: at the

text: University of California, Berkeley

text: . Wake is known for his work on the biology and evolution of

text: salamander

text: s as well as general issues of vertebrate evolutionary biology. He has served as president of the

text: Society for the Study of Evolution

text: , the

text: American Society of Naturalists

text: , and

entity_name: Society for Integrative and Comparative Biology

text: American Society of Zoologists

text: .  He is a member of the

entity_name: American Association for the Advancement of Science

text: American Association for the Advancement of Science

text: , the

text: Linnean Society of London

text: , the

text: American Academy of Arts and Sciences

text: , the

text: American Philosophical Society

text: , and in 1998 was elected into the

text: National Academy of Sciences

text: . He was awarded the 2006

text: Leidy Award

text: from the Academy of Natural Sciences of Philadelphia. He is married to the biologist

text: Marvalee Wake

text: . Wake is commemorated in the names of the salamander

text: Cryptotriton wakei

text: (Wake's moss salamander), the skink genus

text: Davewakeum

text: , the frog genus

text: Wakea

text: , and the lizard

text: Cyrtodactylus wakeorum

text: (Wakes' gecko)—the latter two named jointly after him and his wife.

text: The vertebral column consists of vertebrae, and is divided into three sections: cervical (11-25) (neck), synsacrum (fused vertebrae of the back, also fused to the hips (pelvis)), and pygostyle (tail).

text: The vertebral column consists of vertebrae, and is divided into three sections: cervical (11-25) (neck),

text: synsacrum

text: (fused vertebrae of the back, also fused to the hips (pelvis)), and pygostyle (tail).

text: This species is also known from fossil teeth and some fossilized vertebral centra. Shark skeleton is composed of cartilage and not bone, and cartilage rarely gets fossilized. Hence, fossils of C. chubutensis are generally poorly preserved. Although the teeth of C. chubutensis are morphologically similar to teeth of C. megalodon, they are comparatively slender with curved crown, and with presence of lateral heels feebly serrated. Fossils of this species have been found in North America, South America, Cuba, Puerto Rico, Africa, and Europe.

text: This species is also known from

text: fossil

text: teeth

text: and some fossilized

text: vertebral centra

text: . Shark

text: skeleton

text: is composed of

text: cartilage

text: and not

text: bone

text: , and cartilage rarely gets

text: fossilized

text: . Hence, fossils of C. chubutensis are generally poorly preserved. Although the teeth of C. chubutensis are morphologically similar to teeth of C. megalodon, they are comparatively slender with curved crown, and with presence of lateral heels feebly serrated. Fossils of this species have been found in

text: North America

text: South America

text: Cuba

text: Puerto Rico

text: Africa

text: , and

text: Europe

text: The earliest animals were marine invertebrates, that is, vertebrates came later. Animals are multicellular eukaryotes, and are distinguished from plants, algae, and fungi by lacking cell walls. Marine invertebrates are animals that inhabit a marine environment apart from the vertebrate members of the chordate phylum; invertebrates lack a vertebral column. Some have evolved a shell or a hard exoskeleton.

text: The earliest

text: animal

text: s were marine

text: invertebrate

text: s, that is,

text: vertebrate

text: s came later. Animals are

text: multicellular

text: eukaryote

text: s, and are distinguished from plants, algae, and fungi by lacking

text: cell wall

text: s. Marine invertebrates are animals that inhabit a

text: marine

text: environment apart from the vertebrate members of the

text: chordate

text: phylum; invertebrates lack a

text: vertebral column

text: . Some have evolved a

text: shell

text: or a hard

text: exoskeleton

text: The circulatory systems of all vertebrates are closed, just as in humans. Still, the systems of fish, amphibians, reptiles, and birds show various stages of the evolution of the circulatory system. In fish, the system has only one circuit, with the blood being pumped through the capillaries of the gills and on to the capillaries of the body tissues. This is known as single cycle circulation. The heart of fish is therefore only a single pump (consisting of two chambers). Fish have a closed-loop circulatory system. The heart pumps the blood in a single loop throughout the body. In most fish, the heart consists of four parts, including two chambers and an entrance and exit. The first part is the sinus venosus, a thin-walled sac that collects blood from the fish's veins before allowing it to flow to the second part, the atrium, which is a large muscular chamber. The atrium serves as a one-way antechamber, sends blood to the third part, ventricle. The ventricle is another thick-walled, muscular chamber and it pumps the blood, first to the  fourth part, bulbus arteriosus, a large tube, and then out of the heart. The bulbus arteriosus connects to the aorta, through which blood flows to the gills for oxygenation.

text: The circulatory systems of all

text: vertebrate

text: s are closed, just as in humans. Still, the systems of

text: fish

text: amphibian

text: s,

text: reptile

text: s, and

text: bird

text: s show various stages of the

text: evolution

text: of the

text: circulatory system

text: . In fish, the system has only one circuit, with the blood being pumped through the capillaries of the

text: gill

text: s and on to the capillaries of the body tissues. This is known as single cycle circulation. The heart of fish is therefore only a single pump (consisting of two chambers). Fish have a

text: closed-loop circulatory system

text: . The

text: heart

text: pumps the blood in a single loop throughout the body. In most fish, the heart consists of four parts, including two chambers and an entrance and exit. The first part is the

text: sinus venosus

text: , a thin-walled sac that collects blood from the fish's

text: vein

text: s before allowing it to flow to the second part, the

text: atrium

text: , which is a large muscular chamber. The atrium serves as a one-way antechamber, sends blood to the third part,

text: ventricle

text: . The ventricle is another thick-walled, muscular chamber and it pumps the blood, first to the  fourth part,

text: bulbus arteriosus

text: , a large tube, and then out of the heart. The bulbus arteriosus connects to the

text: aorta

text: , through which blood flows to the gills for oxygenation.

text: Arthritis is a disorder of the joints. It involves inflammation of one or more joints. When affected by arthritis, the joint or joints affected may be painful to move, may move in unusual directions or may be immobile completely. The symptoms of arthritis will vary differently between types of arthritis. The most common form of arthritis: Osteoarthritis can affect both the larger and smaller joints of the human skeleton. The cartilage in the affected joints will degrade, soften and wear away. This decreases the mobility of the joints and decreases the space between bones where cartilage should be.

text: Arthritis is a

text: disorder

text: of the joints. It involves inflammation of one or more joints. When affected by arthritis, the joint or joints affected may be painful to move, may move in unusual directions or may be immobile completely. The symptoms of arthritis will vary differently between types of arthritis. The most common form of arthritis:

text: Osteoarthritis

text: can affect both the larger and smaller joints of the human skeleton. The

text: cartilage

text: in the affected joints will degrade, soften and wear away. This decreases the mobility of the joints and decreases the space between

text: bone

text: s where cartilage should be.

text: At least nine groups of vertebrate OR genes have been identified (α,β,γ,δ,ε,ζ,η, and θ), each of which derived from ancestral genes in the most common ancestor of tetrapods and fish. Specifically, vertebrate OR genes convey an evolutionary pattern of three separate lineages: fish, amphibians, and mammals.

text: At least nine groups of vertebrate OR genes have been identified (α,β,γ,δ,ε,ζ,η, and θ), each of which derived from ancestral genes in the most common ancestor of tetrapods and

text: fish

text: . Specifically, vertebrate OR genes convey an evolutionary pattern of three separate lineages: fish,

text: amphibian

text: s, and mammals.

text: In fish, there is a single membrane known as the primitive meninx. In other vertebrates – amphibians, reptiles and birds, the meninges include a thick outer dura mater and a thick inner secondary meninx. In the early 1900s, Giuseppe Sterzi an Italian anatomist carried out comparative studies on the meninges from the lancelet to man. Contrary to previous reports the spinal meninges were seen to be very simple, both in the adult lower vertebrates and in the early developmental stages of the more advanced vertebrates. From the mesenchyme surrounding the neural tube only a single leaflet forms the primitive meninx. In the following phylogenetic and ontogenetic stages, the latter divides into an internal leaflet: the secondary meninx, and into an external one: the dura mater. Finally, in higher vertebrates, even the secondary meninx divides into the arachnoid and the pia. In the same animals, Sterzi demonstrated that, while in the spinal medulla the dura keeps its identity, in the skull it fuses with the periosteum. He also demonstrated the continuity of all meninges with the envelopes of nerves and with the filum terminale.

text: In

text: fish

text: , there is a single membrane known as the primitive meninx. In other vertebrates –

text: amphibian

text: s,

text: reptile

text: s and

text: bird

text: s, the meninges include a thick outer

text: dura mater

text: and a thick inner secondary meninx. In the early 1900s,

text: Giuseppe Sterzi

text: an Italian anatomist carried out comparative studies on the meninges from the

text: lancelet

text: to man. Contrary to previous reports the spinal meninges were seen to be very simple, both in the adult lower vertebrates and in the early developmental stages of the more advanced vertebrates. From the

text: mesenchyme

text: surrounding the

text: neural tube

text: only a single leaflet forms the primitive meninx. In the following

text: phylogenetic

text: and

text: ontogenetic

text: stages, the latter divides into an internal leaflet: the secondary meninx, and into an external one: the dura mater. Finally, in higher vertebrates, even the secondary meninx divides into the arachnoid and the pia. In the same animals, Sterzi demonstrated that, while in the spinal medulla the dura keeps its identity, in the skull it fuses with the periosteum. He also demonstrated the continuity of all meninges with the envelopes of nerves and with the filum terminale.

text: The vertebral column is often used as a marker of human anatomy. This includes:

text: The

text: vertebral column

text: is often used as a marker of

text: human anatomy

text: . This includes:

text: The musculoskeletal system consists of the human skeleton (which includes bones, ligaments, tendons, and cartilage) and attached muscles. It gives the body basic structure and the ability for movement. In addition to their structural role, the larger bones in the body contain bone marrow, the site of production of blood cells. Also, all bones are major storage sites for calcium and phosphate. This system can be split up into the muscular system and the skeletal system.

text: The

text: musculoskeletal system

text: consists of the

text: human skeleton

text: (which includes

text: bone

text: s,

text: ligament

text: s,

text: tendon

text: s, and

text: cartilage

text: ) and attached

text: muscle

text: s. It gives the body basic structure and the ability for movement. In addition to their structural role, the larger bones in the body contain

text: bone marrow

text: , the site of production of blood cells. Also, all bones are major storage sites for

text: calcium

text: and

text: phosphate

text: . This system can be split up into the

text: muscular system

text: and the

text: skeletal system

text: The psoas minor is a weak flexor of the lumbar vertebral column.

text: In a recent workshop organized by the LDA on "Management of Phumdis" in the Loktak Lake, which involved presentations by locals, the emphasis was on the need to open the barrage for eight months per year (January, April and June–September) to clear the phumdis, control floods and wash away the silt and waste that had accumulated over time. The LDA is also implementing action plans that are economically viable and technically feasible which would result in livelihood enhancement such as evolving an attractive resettlement plan for the phumdi dwellers backed by remunerative livelihood programs and examine the introduction of fishing nets instead of Athapum, the circular shaped Phumdis floating in the lake, planted or cultured artificially for catching fish.

text: Species in this genus have two hosts (a vertebrate and an invertebrate) in their life cycle: for species in this genus the vertebrate host is a fish.

text: Species in this genus have two hosts (a

text: vertebrate

text: and an

text: invertebrate

text: ) in their life cycle: for species in this genus the

text: vertebrate

text: host is a

text: fish

text: Ichnofauna is the diversity of fauna based on the ichnological (tracks and footprints) evidences. This term is often used by vertebrate paleontologists.

text: Ichnofauna is the diversity of fauna based on the ichnological (

text: tracks

text: and

text: footprints

text: ) evidences. This term is often used by vertebrate

text: paleontologists

text: Vertebrate animals were primitively tetrachromatic. They possessed four types of cones—long, mid, short wavelength cones, and ultraviolet sensitive cones.  Today, fish, reptiles and birds are all tetrachromatic. Placental mammals lost both the mid and short wavelength cones. Thus, most mammals do not have complex color vision—they are dichromatic but they are sensitive to ultraviolet light, though they cannot see its colors. Human trichromatic color vision is a recent evolutionary novelty that first evolved in the common ancestor of the Old World Primates. Our trichromatic color vision evolved by duplication of the long wavelength sensitive opsin, found on the X chromosome. One of these copies evolved to be sensitive to green light and constitutes our mid wavelength opsin. At the same time, our short wavelength opsin evolved from the ultraviolet opsin of our vertebrate and mammalian ancestors.

text: Vertebrate animals were primitively

text: tetrachromatic

text: . They possessed four types of cones—long, mid, short wavelength cones, and ultraviolet sensitive cones.  Today, fish, reptiles and birds are all tetrachromatic. Placental mammals lost both the mid and short wavelength cones. Thus, most mammals do not have complex color vision—they are

text: dichromatic

text: but they are sensitive to ultraviolet light, though they cannot see its colors. Human trichromatic color vision is a recent evolutionary novelty that first evolved in the common ancestor of the Old World Primates. Our trichromatic color vision evolved by duplication of the long wavelength sensitive

text: opsin

text: , found on the X chromosome. One of these copies evolved to be sensitive to green light and constitutes our mid wavelength opsin. At the same time, our short wavelength opsin evolved from the ultraviolet opsin of our vertebrate and mammalian ancestors.

text: The first proto-eyes evolved among animals  about the time of the Cambrian explosion. The last common ancestor of animals possessed the biochemical toolkit necessary for vision, and more advanced eyes have evolved in 96% of animal species in six of the ~35 main phyla. In most vertebrates and some molluscs, the eye works by allowing light to enter and project onto a light-sensitive panel of cells, known as the retina, at the rear of the eye. The cone cells (for colour) and the rod cells (for low-light contrasts) in the retina detect and convert light into neural signals for vision. The visual signals are then transmitted to the brain via the optic nerve. Such eyes are typically roughly spherical, filled with a transparent gel-like substance called the vitreous humour, with a focusing lens and often an iris; the relaxing or tightening of the muscles around the iris change the size of the pupil, thereby regulating the amount of light that enters the eye, and reducing aberrations when there is enough light. The eyes of most cephalopods, fish, amphibians and snakes have fixed lens shapes, and focusing vision is achieved by telescoping the lens—similar to how a camera focuses.

text: The first proto-eyes evolved among animals  about the time of the

text: Cambrian explosion

text: . The last common ancestor of animals possessed the biochemical toolkit necessary for vision, and more advanced eyes have evolved in 96% of animal species in six of the ~35 main

text: phyla

text: . In most

text: vertebrate

text: s and some

text: mollusc

text: s, the eye works by allowing light to enter and project onto a light-sensitive panel of

text: cells

text: , known as the

text: retina

text: , at the rear of the eye. The

text: cone cell

text: s (for colour) and the

text: rod cell

text: s (for low-light contrasts) in the retina detect and convert light into neural signals for vision. The visual signals are then transmitted to the

text: brain

text: via the

text: optic nerve

text: . Such eyes are typically roughly spherical, filled with a

text: transparent

text: gel-like substance called the

text: vitreous humour

text: , with a focusing

text: lens

text: and often an

text: iris

text: ; the relaxing or tightening of the muscles around the iris change the size of the

text: pupil

text: , thereby regulating the amount of light that enters the eye, and reducing aberrations when there is enough light. The eyes of most

text: cephalopod

text: s,

text: fish

text: amphibian

text: s and

text: snake

text: s have fixed lens shapes, and focusing vision is achieved by telescoping the lens—similar to how a

text: camera

text: focuses.

text: More recent studies demonstrated that mice use a different family of cell recognition molecules: clustered Protocadherins (Pcdhs), in a fly Dscam1-like strategy to regulate self-avoidance. Although both clustered Pcdhs and Dscam1 genes generate families of proteins with diverse ectodomains joined to a common cytoplasmic domain, the mode of generating clustered Pcdhs and fly Dscam1 counterpart diversity is markedly different. Pcdhs diversity is largely generated by alternative promoter choice, as opposed to alternative splicing.The number of Pcdhs isoforms varies between different vertebrate species, but in aggregate, there are typically on the order of 50 isoforms.

text: More recent studies demonstrated that mice use a different family of cell recognition molecules: clustered

text: Protocadherins (Pcdhs)

text: , in a fly Dscam1-like strategy to regulate self-avoidance. Although both clustered Pcdhs and Dscam1 genes generate families of proteins with diverse ectodomains joined to a common cytoplasmic domain, the mode of generating clustered Pcdhs and fly Dscam1 counterpart diversity is markedly different. Pcdhs diversity is largely generated by alternative promoter choice, as opposed to alternative splicing.The number of Pcdhs isoforms varies between different vertebrate species, but in aggregate, there are typically on the order of 50 isoforms.

text: The sternoclavicular joint  or sternoclavicular articulation is the joint between the manubrium of the sternum and the clavicle bone. It is structurally classed as a saddle joint and functionally classed as a synovial joint. It is composed of two portions separated by an articular disc of fibrocartilage. The bone areas entering into its formation are the sternal end of the clavicle, the upper and lateral part of the sternum, (the clavicular notch), and the cartilage of the first rib, visible from the outside as the suprasternal notch. The articular surface of the clavicle is much larger than that of the sternum, and is invested with a layer of cartilage, which is considerably thicker than that on the sternum.

text: The sternoclavicular joint  or sternoclavicular articulation is the

text: joint

text: between the

text: manubrium of the sternum

text: and the

text: clavicle bone

text: . It is structurally classed as a

text: saddle joint

text: and functionally classed as a

text: synovial joint

text: . It is composed of two portions separated by an

text: articular disc

text: of

text: fibrocartilage

text: . The bone areas entering into its formation are the sternal end of the clavicle, the upper and lateral part of the sternum, (the

text: clavicular notch

text: ), and the cartilage of the

text: first rib

text: , visible from the outside as the

text: suprasternal notch

text: . The articular surface of the clavicle is much larger than that of the sternum, and is invested with a layer of cartilage, which is considerably thicker than that on the sternum.

text: Anchiceratops specimens are found in the upper part of Unit one of this formation, part of the Horsetheif member, dated to about 72-71 million years ago. Anchiceratops shared its paleoenvironment with other dinosaurs, such as maniraptorans (Epichirostenotes curriei), ornithomimids (Ornithomimus edmontonicus), pachycephalosaurids (Sphaerotholus edmontonensis), hadrosaurids (Edmontosaurus regalis), ceratopsians (Pachyrhinosaurus canadensis), and unidentified tyrannosaurids, which were apex predators. Of these, the hadrosaurs dominated in terms of shear number and made up half of all dinosaurs who lived in this region. Other vertebrates present in the Horseshoe Canyon Formation at the time of Anchiceratops included reptiles, and amphibians. Sharks, rays, sturgeons, bowfins, gars and the gar-like Aspidorhynchus made up the fish fauna.  Reptiles such as turtles and crocodilians are rare in the Horseshoe Canyon Formation, and this was thought to reflect the relatively cool climate which prevailed at the time.  A study by Quinney et al. (2013) however, showed that the decline in turtle diversity, which was previously attributed to climate, coincided instead with changes in soil drainage conditions, and was limited by aridity, landscape instability, and migratory barriers.   The saltwater plesiosaur Leurospondylus was present and freshwater environments were populated by turtles, Champsosaurus, and crocodilians like Leidyosuchus and Stangerochampsa.  Evidence has shown that multituberculates and the early marsupial Didelphodon coyi were present.  Vertebrate trace fossils from this region included the tracks of theropods, ceratopsians and ornithopods, which provide evidence that these animals were also present. 	Non-vertebrates in this ecosystem included both marine and terrestrial invertebrates.

text: Anchiceratops specimens are found in the upper part of Unit one of this formation, part of the Horsetheif member, dated to about 72-71 million years ago. Anchiceratops shared its

text: paleoenvironment

text: with other dinosaurs, such as

text: maniraptoran

text: s (

text: Epichirostenotes curriei

text: ornithomimids

text: Ornithomimus edmontonicus

text: pachycephalosaurids

text: Sphaerotholus edmontonensis

text: hadrosaurids

text: Edmontosaurus regalis

text: ceratopsians

text: Pachyrhinosaurus canadensis

text: ), and unidentified

text: tyrannosaurids

text: , which were

text: apex predators

text: . Of these, the hadrosaurs dominated in terms of shear number and made up half of all dinosaurs who lived in this region. Other vertebrates present in the Horseshoe Canyon Formation at the time of Anchiceratops included

text: reptile

text: s, and

text: amphibian

text: s.

text: Shark

text: s,

text: rays

text: sturgeon

text: s,

text: bowfin

text: s,

text: gar

text: s and the gar-like

text: Aspidorhynchus

text: made up the fish fauna.  Reptiles such as turtles and crocodilians are rare in the Horseshoe Canyon Formation, and this was thought to reflect the relatively cool climate which prevailed at the time.  A study by Quinney et al. (2013) however, showed that the decline in turtle diversity, which was previously attributed to climate, coincided instead with changes in soil drainage conditions, and was limited by aridity, landscape instability, and migratory barriers.   The saltwater

text: plesiosaur

text: Leurospondylus

text: turtle

text: s,

text: Champsosaurus

text: , and

text: crocodilia

text: ns like

text: Leidyosuchus

text: and

text: Stangerochampsa

text: .  Evidence has shown that

text: multituberculate

text: s and the early

text: marsupial

text: Didelphodon

text: theropods

text: ceratopsians

text: and

text: ornithopods

text: , which provide evidence that these animals were also present. 	Non-vertebrates in this ecosystem included both marine and terrestrial

text: invertebrate

text: s.

text: Monge-Nájera's studies with vertebrates asked similar questions to those he studied in invertebrates (what characteristics allow a species to live in a particular habitat, and how those characteriscs evolved), but were done with turtles, snakes, birds and mammals. The study of the semiaquatic turtle Rhinoclemmys pulcherrima described behavioral adaptations to their moist habitat, and the redescription of the venomous snake Bothriechis supraciliaris included a morphometric study of geographic variation in related snakes. The question of why brown quetzal feathers are perceived as green by the human eye also considered how such adaptation can work in the moist ecosystems inhabited by these birds. Even though his work with birds was minimal, he edited and coauthored a book about how birds and other organisms might have participated in the development of music, Music Origins. Gastric bacteria in mammals were the basis for a cladogram of how the bacteria could have evolved. Why coyotes could expand their geographic range in the last centuries rejected the hypothesis that it was caused by deforestation.

text: While this traditional classification is orderly, most of the groups are paraphyletic, i.e. do not contain all descendants of the class' common ancestor. For instance, descendants of the first reptiles include modern reptiles as well as mammals and birds. Most of the classes listed are not "complete" (and are therefore paraphyletic) taxa, meaning they do not include all the descendants of the first representative of the group. For example, the agnathans have given rise to the jawed vertebrates; the bony fishes have given rise to the land vertebrates; the traditional "amphibians" have given rise to the reptiles (traditionally including the synapsids, or mammal-like "reptiles"), which in turn have given rise to the mammals and birds. Most scientists working with vertebrates use a classification based purely on phylogeny, organized by their known evolutionary history and sometimes disregarding the conventional interpretations of their anatomy and physiology.

text: While this traditional classification is orderly, most of the groups are

text: paraphyletic

text: , i.e. do not contain all descendants of the class' common ancestor. For instance, descendants of the first reptiles include modern reptiles as well as mammals and birds. Most of the classes listed are not "complete" (and are therefore paraphyletic)

text: taxa

text: , meaning they do not include all the descendants of the first representative of the group. For example, the

text: agnatha

text: ns have given rise to the

text: jawed vertebrates

text: ; the

text: bony fishes

text: have given rise to the

text: land vertebrates

text: ; the traditional "

text: amphibians

text: " have given rise to the

text: reptiles

text: (traditionally including the

text: synapsid

text: s, or mammal-like "reptiles"), which in turn have given rise to the mammals and birds. Most scientists working with vertebrates use a classification based purely on

text: phylogeny

text: , organized by their known evolutionary history and sometimes disregarding the conventional interpretations of their anatomy and physiology.

text: There was a persistent debate during the twentieth century as to whether the vertebrate head is “old” or “new”. Scientists who champion the idea of an “old” head suggest that the vertebrate head resulted from the evolution of important modifications to a previously existing head. The idea of a "new" vertebrate head was proposed originally by American vertebrate morphologists Carl Gans and Glenn Northcutt in 1983. They suggested that the vertebrate head is a new structure, which has no corresponding structure in close relatives such as Branchiostoma.

text: There was a persistent debate during the twentieth century as to whether the vertebrate head is “old” or “new”. Scientists who champion the idea of an “old” head suggest that the vertebrate head resulted from the evolution of important modifications to a previously existing head. The idea of a "new" vertebrate head was proposed originally by American vertebrate morphologists Carl Gans and

text: Glenn Northcutt

text: in 1983. They suggested that the vertebrate head is a new structure, which has no corresponding structure in close relatives such as Branchiostoma.

text: The zygosphen-zygantrum joint function to stabilize the vertebral column. While it permits horizontal and vertical movements of the vertebral column, it prevents rotations of the single vertebrae against each other.

text: The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male. A female individual cannot reproduce sexually without access to the gametes of a male (an exception is parthenogenesis). Some organisms can reproduce both sexually and asexually.

text: The

text: ova

text: are defined as the larger

text: gamete

text: s in a

text: heterogamous

text: reproduction system

text: , while the smaller, usually

text: motile

text: gamete, the

text: spermatozoon

text: , is produced by the

text: male

text: . A female individual cannot reproduce

text: sexually

text: without access to the gametes of a male (an exception is

text: parthenogenesis

text: ). Some organisms can reproduce both sexually and

text: asexually

text: Although apparently doing well in its location, the species is considered vulnerable because of its very limited range in a fragile environment. Having evolved without any competition, there is concern over the possible effects of exotic fish introduction, whether deliberate or accidental.

text: Although apparently doing well in its location, the species is considered vulnerable because of its very limited range in a fragile

text: environment

text: . Having

text: evolved

text: without any competition, there is concern over the possible effects of

text: exotic fish introduction

text: , whether deliberate or accidental.

text: Many species reproduce asexually by way of parthenogenesis, wherein females lay eggs without mating and males are absent or rare.

text: Many species reproduce asexually by way of

text: parthenogenesis

text: , wherein females lay eggs without mating and males are absent or rare.

text: In the wild, five species of Ambystoma salamanders contribute to a unisexual complex that reproduces via a combination of gynogenesis and kleptogenesis: A. tigrinum, A. barbouri, A. texanum, A. jeffersonium, and A. laterale. Over twenty genomic combinations have been found in nature, ranging from "LLJ"  individuals (two A. laterale and an A. jeffersonium genome) to "LJTi" individuals (an A. laterale, A. jeffersonium, and an A. tigrinum genome). Every combination, however, contains the genetic information from the A. laterale species, and analysis of mitochondrial DNA has indicated that these unisexual species most likely diverged from an A. barbouri individual some 5 million years ago, making them the oldest unisexual vertebrate species on Earth

text: In the wild, five species of

text: Ambystoma

text: salamanders contribute to a unisexual complex that reproduces via a

entity_section: Modes of parthenogenesis and parthenogenetic-like reproduction in amphibians

text: combination of gynogenesis and kleptogenesis

text: : A. tigrinum, A. barbouri, A. texanum, A. jeffersonium, and A. laterale. Over twenty genomic combinations have been found in nature, ranging from "LLJ"  individuals (two A. laterale and an A. jeffersonium genome) to "LJTi" individuals (an A. laterale, A. jeffersonium, and an A. tigrinum genome). Every combination, however, contains the genetic information from the A. laterale species, and analysis of mitochondrial DNA has indicated that these unisexual species most likely diverged from an A. barbouri individual some 5 million years ago, making them the oldest unisexual vertebrate species on Earth

text: A growth center is located in the head of each mandibular condyle before an individual reaches maturity. This growth center consists of hyaline cartilage underneath the periosteum on the articulating surface of the condyle. This is the last growth center of bone in the body and is multidirectional in its growth capacity, unlike a typical long bone. This area of cartilage within the bone grows in length by appositional growth as the individual grows to maturity. Over time, the cartilage is replaced by bone, using endochondral ossification. This mandibular growth center in the condyle allows the increased length of the mandible needed for the larger permanent teeth, as well as for the larger brain capacity of the adult. This growth of the mandible also influences the overall shape of the face, and thus is charted and referred to during orthodontic therapy. When an individual reaches full maturity, the growth center of bone within the condyle has disappeared.

text: Oikopleura dioica (class Appendicularia) is a semelparous organism, reproducing only once in its lifetime.  It employs an original reproductive strategy in which the entire female germ-line is contained within an ovary that is a single giant multinucleate cell termed the "coenocyst".  O.  dioica can be maintained in laboratory culture, and is of growing interest as a model organism because of its phylogenetic position within the closest sister group to vertebrates.

text: Oikopleura dioica

text: (class

text: Appendicularia

text: ) is a

text: semelparous

text: organism, reproducing only once in its lifetime.  It employs an original

text: reproductive strategy

text: in which the entire female

text: germ-line

text: is contained within an ovary that is a single giant

text: multinucleate

text: cell termed the "coenocyst".  O.  dioica can be maintained in laboratory culture, and is of growing interest as a

text: model organism

text: because of its

text: phylogenetic

text: position within the closest sister group to

text: vertebrates

text: A study on deforestation in the Amazon looked at two patterns of habitat fragmentation: "fish-bone" in smaller properties and another unnamed large property pattern. The large property pattern contained fewer fragments than the smaller fish-bone pattern. The results suggested that higher levels of fragmentation within the fish-bone pattern led to the loss of species and decreased diversity of large vertebrates. Human impacts, such as the fragmentation of forests, may cause large areas to lose the ability to maintain biodiversity and ecosystem function due to loss of key ecological processes. This can consequently cause changes within environments and skew evolutionary processes.

text: A study on

text: deforestation in the Amazon

text: looked at two patterns of habitat fragmentation: "fish-bone" in smaller properties and another unnamed large property pattern. The large property pattern contained fewer fragments than the smaller fish-bone pattern. The results suggested that higher levels of fragmentation within the fish-bone pattern led to the loss of species and decreased diversity of large vertebrates. Human impacts, such as the fragmentation of forests, may cause large areas to lose the ability to maintain

text: biodiversity

text: and ecosystem function due to loss of key ecological processes. This can consequently cause changes within environments and skew evolutionary processes.

text: It was initially thought that cartilage conduction was a type of bone conduction. However, several studies demonstrated that the mechanisms of cartilage conduction differ from that of bone conduction. Bone conduction is attributed to bone vibration at the skull, which is transmitted to the inner ear. In contrast, cartilage conduction is accounted for by sound (vibration) energy stimulating the cartilage at the external auditory canal to create sonic waves in the ear canal. Such sonic wave energy passes through the eardrum and the middle ear before finally activating the auditory nerve. These different mechanisms would explain the following observed differences between cartilage and bone pathways:

text: The axial skeleton is the part of the skeleton that consists of the bones of the head and trunk of a vertebrate.  In the human skeleton, it consists of 80 bones and is composed of six parts; the skull bones, the ossicles of the middle ear, the hyoid bone, the rib cage, sternum and the vertebral column.  The axial skeleton together with the appendicular skeleton form the complete skeleton. Another definition of axial skeleton is the bones including the vertebrae, sacrum, coccyx, ribs, and sternum.

text: The axial skeleton is the part of the

text: skeleton

text: that consists of the

text: bone

text: s of the

text: head

text: and

text: trunk

text: of a

text: vertebrate

text: .  In the

text: human skeleton

text: , it consists of 80 bones and is composed of six parts; the

text: skull

text: bones, the

text: ossicles

text: of the

text: middle ear

text: , the

text: hyoid bone

text: , the

text: rib cage

text: sternum

text: and the

text: vertebral column

text: .  The axial skeleton together with the

text: appendicular skeleton

text: form the complete skeleton. Another definition of axial skeleton is the bones including the vertebrae, sacrum, coccyx, ribs, and sternum.

text: The term "cyberchondria" is a portmanteau neologism derived from the terms cyber- and hypochondria. (The term "hypochondrium" derives from Greek and literally means the region below the "cartilage" or "breast bone.") Researchers at Harris Interactive clarified the etymology of cyberchondria, and state in studies and interviews that the term is not necessarily intended to be pejorative.

text: The term "cyberchondria" is a

text: portmanteau

text: neologism

text: derived from the terms

text: cyber-

text: and

text: hypochondria

text: . (The term "

text: hypochondrium

text: " derives from Greek and literally means the region below the "

text: cartilage

text: " or "

text: breast bone

text: .") Researchers at Harris Interactive clarified the

text: etymology

text: of cyberchondria, and state in studies and interviews that the term is not necessarily intended to be

text: pejorative

text: The vertebrate jaw probably originally evolved in the Silurian period and appeared in the Placoderm fish which further diversified in the Devonian.  Jaws are thought to derive from the pharyngeal arches that support the gills in fish.  The two most anterior of these arches are thought to have become the jaw itself (see hyomandibula) and the hyoid arch, which braces the jaw against the braincase and increases mechanical efficiency.  While there is no fossil evidence directly to support this theory, it makes sense in light of the numbers of pharyngeal arches that are visible in extant jawed (the Gnathostomes), which have seven arches, and primitive jawless vertebrates (the Agnatha), which have nine.

text: The vertebrate jaw probably originally evolved in the

text: Silurian

text: period and appeared in the

text: Placoderm

text: fish

text: which further diversified in the

text: Devonian

text: .  Jaws are thought to derive from the

text: pharyngeal arch

text: es that support the

text: gills

text: in fish.  The two most anterior of these arches are thought to have become the jaw itself (see

text: hyomandibula

text: ) and the hyoid arch, which braces the jaw against the braincase and increases mechanical efficiency.  While there is no fossil evidence directly to support this theory, it makes sense in light of the numbers of pharyngeal arches that are visible in extant jawed (the

text: Gnathostomes

text: ), which have seven arches, and primitive jawless vertebrates (the

text: Agnatha

text: ), which have nine.

text: Research has shown that the flying fish has undergone morphological changes throughout its history, the first of which is fully broadened neural arches. Neural arches act as insertion sites for muscles, connective tissues, and ligaments in a fish’s skeleton. Fully broadened neural arches act as more stable and sturdier sites for these connections, creating a strong link between the vertebral column and cranium. This ultimately allows a rigid and sturdy vertebral column (body) that is beneficial in flight. Having a rigid body during glided flight gives the flying fish aerodynamic advantages, increasing its speed and improving its aim. Furthermore, flying fish have developed vertebral columns and ossified caudal complexes. These features provide the majority of strength to the flying fish, allowing them to physically lift their body out of water and glide remarkable distances. These additions also reduce the flexibility of the flying fish, allowing them to perform powerful leaps without weakening midair. At the end of a glide, it folds its pectoral fins to re-enter the sea, or drops its tail into the water to push against the water to lift itself for another glide, possibly changing direction. The curved profile of the "wing" is comparable to the aerodynamic shape of a bird wing. The fish is able to increase its time in the air by flying straight into or at an angle to the direction of updrafts created by a combination of air and ocean currents.

text: Research has shown that the flying fish has undergone morphological changes throughout its history, the first of which is fully broadened

text: neural arches

text: . Neural arches act as insertion sites for muscles, connective tissues, and ligaments in a fish’s skeleton. Fully broadened neural arches act as more stable and sturdier sites for these connections, creating a strong link between the vertebral column and cranium. This ultimately allows a rigid and sturdy vertebral column (body) that is beneficial in flight. Having a rigid body during glided flight gives the flying fish aerodynamic advantages, increasing its speed and improving its aim. Furthermore, flying fish have developed vertebral columns and ossified caudal complexes. These features provide the majority of strength to the flying fish, allowing them to physically lift their body out of water and glide remarkable distances. These additions also reduce the flexibility of the flying fish, allowing them to perform powerful leaps without weakening midair. At the end of a glide, it folds its pectoral fins to re-enter the sea, or drops its tail into the water to push against the water to lift itself for another glide, possibly changing direction. The curved profile of the "wing" is comparable to the aerodynamic shape of a bird wing. The fish is able to increase its time in the air by flying straight into or at an angle to the direction of

text: updraft

text: s created by a combination of

text: air

text: and

text: ocean current

text: s.

text: The lancelets (from "lancet") — also known as amphioxi (singular, amphioxus) — comprise some 32 species of fish-like marine chordates in the order Amphioxiformes, with a global distribution in shallow temperate (as far north as Scotland) and tropical seas, usually found half-buried in sand. They are the modern representatives of the subphylum Cephalochordata, formerly thought to be the sister group of the craniates. In Asia, they are harvested commercially as food for humans and domesticated animals. They are an important object of study in zoology as they provide indications about the evolutionary origins of the vertebrates. Lancelets serve as an intriguing comparison point for tracing how vertebrates have evolved and adapted. Although lancelets split from vertebrates more than 520 million years ago, their genomes hold clues about evolution, particularly how vertebrates have employed old genes for new functions. They are regarded as similar to the archetypal vertebrate form.

text: The lancelets (from "lancet") — also known as amphioxi (singular, amphioxus) — comprise some 32 species of fish-like marine

text: chordates

text: in the order Amphioxiformes, with a global distribution in shallow

text: temperate

text: (as far north as

text: Scotland

text: ) and

text: tropical

text: sea

text: s, usually found half-buried in sand. They are the modern representatives of the subphylum

text: Cephalochordata

text: , formerly thought to be the sister group of the

text: craniate

text: s. In

text: Asia

text: , they are harvested commercially as

text: food

text: for

text: human

text: s and

text: domesticated animal

text: s. They are an important object of study in

text: zoology

text: as they provide indications about the evolutionary origins of the

text: vertebrate

text: s. Lancelets serve as an intriguing comparison point for tracing how vertebrates have evolved and adapted. Although lancelets split from vertebrates more than 520 million years ago, their genomes hold clues about evolution, particularly how vertebrates have employed old genes for new functions. They are regarded as similar to the archetypal vertebrate form.

text: Therefore, the successful rhinoplastic outcome depends entirely upon the respective maintenance or restoration of the anatomic integrity of the nasal skeleton, which comprises (a) the nasal bones and the ascending processes of the maxilla in the upper third; (b) the paired upper-lateral cartilages in the middle third; and (c) the lower-lateral, alar cartilages in the lower third. Hence, managing the surgical reconstruction of a damaged, defective, or deformed nose, requires that the plastic surgeon manipulate three (3) anatomic layers:

text: The sides of the vertebral column are separated from the posterior surface by the articular processes in the cervical and thoracic regions, and by the transverse processes in the lumbar region. In the thoracic region, the sides of the bodies of the vertebrae are marked in the back by the facets for articulation with the heads of the ribs. More posteriorly are the intervertebral foramina, formed by the juxtaposition of the vertebral notches, oval in shape, smallest in the cervical and upper part of the thoracic regions, and gradually increasing in size to the last lumbar. They transmit the special spinal nerves and are situated between the transverse processes in the cervical region, and in front of them in the thoracic and lumbar regions.

text: Like all sauropods, Brachiosaurus was homeothermic (maintaining a stable internal temperature) and endothermic (controlling body temperature through internal means), meaning that it was able to actively control its body temperature ("warm-blooded"), producing the necessary heat through a high basic metabolic rate of its cells. In the past, Brachiosaurus has been used an example of a dinosaur for which endothermy is unlikely, because of the combination of great size (leading to overheating) and great caloric needs to fuel endothermy. However, these calculations were based on incorrect assumptions about the available cooling surfaces (the large air sacs were not known), and a grossly inflated body mass. These inaccuracies resulted in the overestimation of heat production and the underestimation of heat loss. The large nasal arch has been postulated as an adaptation for cooling the brain, as a surface for evaporative cooling of the blood.

text: Like all sauropods, Brachiosaurus was

text: homeothermic

text: (maintaining a stable internal temperature) and

text: endothermic

text: (controlling body temperature through internal means), meaning that it was able to actively control its body temperature ("

text: warm-blooded

text: "), producing the necessary heat through a high

text: basic metabolic rate

text: of its cells. In the past, Brachiosaurus has been used an example of a dinosaur for which endothermy is unlikely, because of the combination of great size (leading to overheating) and great

text: caloric

text: needs to fuel endothermy. However, these calculations were based on incorrect assumptions about the available cooling surfaces (the large air sacs were not known), and a grossly inflated body mass. These inaccuracies resulted in the overestimation of heat production and the underestimation of heat loss. The large nasal arch has been postulated as an adaptation for cooling the brain, as a surface for evaporative cooling of the blood.

text: Adult reproduce sexually by spawning in spring and the neotenous form reproduce asexually by transverse binary fission.

text: Adult reproduce sexually by

text: spawning

text: in spring and the neotenous form reproduce asexually by transverse

text: binary fission

text: Females of the Apatosaurus and Diplodocus species have an interconnected caudal vertebrate that allows them to keep their tails elevated to aid in copulation. Discovering that this fusion occurred in only 50% of the Apatosaurus and Diplodocus skeletons and 25% of the Camarasaurus skeletons, indicated that this is a sexually dimorphic trait.

text: Females of the

text: Apatosaurus

text: and

text: Diplodocus

text: species have an interconnected

text: caudal vertebrate

text: that allows them to keep their tails elevated to aid in copulation. Discovering that this fusion occurred in only 50% of the Apatosaurus and Diplodocus skeletons and 25% of the

text: Camarasaurus

text: skeletons, indicated that this is a sexually dimorphic trait.

text: In the developing vertebrate embryo, somites split to form dermatomes, skeletal muscle (myotomes), tendons and cartilage (syndetomes) and bone (sclerotomes).

text: In the developing vertebrate

text: embryo

text: , somites split to form dermatomes, skeletal muscle (myotomes),

text: tendon

text: s and cartilage (syndetomes) and

text: bone

text: (sclerotomes).

text: After gastrulation, neural crest cells are specified at the border of the neural plate and the non-neural ectoderm.  During neurulation, the borders of the neural plate, also known as the neural folds, converge at the dorsal midline to form the neural tube.  Subsequently, neural crest cells from the roof plate of the neural tube undergo an epithelial to mesenchymal transition, delaminating from the neuroepithelium and migrating through the periphery where they differentiate into varied cell types.  The emergence of neural crest was important in vertebrate evolution because many of its structural derivatives are defining features of the vertebrate clade.

text: After

text: gastrulation

text: , neural crest cells are specified at the border of the neural plate and the non-neural

text: ectoderm

text: .  During

text: neurulation

text: , the borders of the neural plate, also known as the

text: neural fold

text: s, converge at the dorsal midline to form the

text: neural tube

text: .  Subsequently, neural crest cells from the roof plate of the neural tube undergo an

text: epithelial to mesenchymal transition

text: , delaminating from the neuroepithelium and migrating through the periphery where they differentiate into varied cell types.  The emergence of neural crest was important in vertebrate evolution because many of its structural derivatives are defining features of the vertebrate clade.

text: A 2009 study supported the hypothesis that endothermy was widespread in at least larger non-avian dinosaurs, and that It was plausibly ancestral for all dinosauriforms, based on the biomechanics of running.

text: Sarahsaurus shared its paleoenvironment with other dinosaurs, such as several theropods including Dilophosaurus, Kayentavenator, Megapnosaurus kayentakatae, the "Shake N Bake" theropod, and the armored dinosaurs Scelidosaurus and Scutellosaurus.   The Kayenta formation has produced that remains of three coelophysoid taxa of different body size,which represents the most diverse ceratosaur fauna yet known. The Kayenta Formation has yielded a small but growing assemblage of organisms. Vertebrates present in the Kayenta Formation at the time of Saharasaurus included hybodont sharks, bony fish known as osteichthyes, lungfish, salamanders, the frog Prosalirus, the caecilian Eocaecilia, the turtle Kayentachelys, a sphenodontian reptile, various lizards.  Also present were, the synapsids Dinnebiton, Kayentatherium, and Oligokyphus., several early crocodylomorphs including Calsoyasuchus, Eopneumatosuchus, Kayentasuchus, and Protosuchus, and the pterosaur Rhamphinion. The possible presence of the early true mammal Dinnetherium, and a haramyid mammal has also been proposed, based on fossil finds. Vertebrate trace fossils from this area included coprolites and the tracks of therapsids, lizard-like animals, and dinosaurs, which provided evidence that these animals were also present. Non-vertebrates in this ecosystem included microbial or "algal" limestone, freshwater bivalves, freshwater mussels and snails, and ostracods. The plant life known from this area included trees that became preserved as petrified wood.

text: Sarahsaurus shared its

text: paleoenvironment

text: with other dinosaurs, such as several theropods including Dilophosaurus,

text: Kayentavenator

text: Megapnosaurus kayentakatae

text: , the "Shake N Bake" theropod, and the armored dinosaurs

text: Scelidosaurus

text: and

text: Scutellosaurus

text: .   The Kayenta formation has produced that remains of three coelophysoid taxa of different body size,which represents the most diverse ceratosaur fauna yet known. The Kayenta Formation has yielded a small but growing assemblage of organisms. Vertebrates present in the Kayenta Formation at the time of Saharasaurus included

text: hybodont

text: sharks,

text: bony fish

text: known as osteichthyes,

text: lungfish

text: , salamanders, the frog

text: Prosalirus

text: , the

text: caecilia

text: n

text: Eocaecilia

text: , the turtle

text: Kayentachelys

text: , a

text: sphenodontia

text: n reptile, various lizards.  Also present were, the

text: synapsids

text: Dinnebiton

text: Kayentatherium

text: , and

text: Oligokyphus

text: ., several early

text: crocodylomorphs

text: including

text: Calsoyasuchus

text: Eopneumatosuchus

text: Kayentasuchus

text: , and

text: Protosuchus

text: , and the

text: pterosaur

text: Rhamphinion

text: . The possible presence of the early true mammal Dinnetherium, and a haramyid mammal has also been proposed, based on fossil finds. Vertebrate trace fossils from this area included

text: coprolite

text: s and the tracks of

text: therapsid

text: s, lizard-like animals, and dinosaurs, which provided evidence that these animals were also present. Non-vertebrates in this ecosystem included microbial or "algal" limestone, freshwater bivalves, freshwater mussels and snails, and

text: ostracod

text: s. The plant life known from this area included trees that became preserved as petrified wood.

text: The development of children’s feet begins in-utero, being mainly derived from basic embryological tissue called mesenchyme. In simple terms, the mesenchyme differentiates to form a cartilage foot template, which is largely complete by the end of the embryonic period (8 weeks after conception). The lower limb buds appear around the 4th embryonic  week, slightly later than the upper limb buds, and the developing nervous system is already evident. The blood supply of the foot then begins to infiltrate the tarsal bones, whilst the process of endochondral ossification sees cartilage become bone. Not all of the foot bones are formed at birth. The navicular is the last bone to ossify, occurring between 2 and 5 years of age. The ossification of the cuboid occurs reliably at 37 weeks gestation and its appearance is often used as a marker of foetal maturity. At birth of a ‘full-term’ baby the average foot length is 7.6 centimetres (range 7.1  – 8.7 cm). Foot growth continues to be very rapid in the first 5 years of life; slower development continues until skeletal maturity of the feet, which occurs on average at 13 years in girls and 15 years in boys. Final foot length is achieved before maximum height is reached in both genders.

text: The development of children’s feet begins in-utero, being mainly derived from basic embryological tissue called

text: mesenchyme

text: . In simple terms, the mesenchyme differentiates to form a

text: cartilage

text: foot template, which is largely complete by the end of the embryonic period (8 weeks after conception). The lower limb buds appear around the 4th embryonic  week, slightly later than the upper limb buds, and the developing

text: nervous system

text: is already evident. The

text: blood

text: supply of the foot then begins to infiltrate the

text: tarsal bones

text: , whilst the process of endochondral ossification sees cartilage become bone. Not all of the foot bones are formed at birth. The

text: navicular

text: is the last bone to ossify, occurring between 2 and 5 years of age. The

text: ossification

text: of the

text: cuboid

text: occurs reliably at 37 weeks gestation and its appearance is often used as a marker of foetal maturity. At birth of a ‘full-term’ baby the average foot length is 7.6 centimetres (range 7.1  – 8.7 cm). Foot growth continues to be very rapid in the first 5 years of life; slower development continues until skeletal maturity of the feet, which occurs on average at 13 years in girls and 15 years in boys. Final foot length is achieved before maximum height is reached in both genders.

text: The cervical intersegmental arteries merge into the vertebral artery with the exception of the 7th (or possibly the 6th) cervical intersegmental artery, which becomes the subclavian artery. The confusion arises because the vertebral artery drains into the subclavian artery following the disappearance of the dorsal aortae in part of the cervical region.

text: The cervical intersegmental arteries merge into the

text: vertebral artery

text: with the exception of the 7th (or possibly the 6th) cervical intersegmental artery, which becomes the

text: subclavian artery

text: . The confusion arises because the vertebral artery drains into the subclavian artery following the disappearance of the dorsal aortae in part of the cervical region.

text: MHC diversity in vertebrates may also be generated by the recombination of alleles on the MHC gene.

text: The vertebral column of Scipionyx probably includes ten cervical vertebrae and thirteen dorsal vertebrae; due to the fact the specimen is just a hatchling, the differentiation between the two categories has not fully developed, making any distinction rather arbitrary. With certainty five sacral vertebrae are present. The fossil has preserved just nine tail vertebrae; likely fifty or more had been originally present. The neck vertebrae are opisthocoelous. The axis is pneumatised as a pneumatopore, an opening through which a diverticulum of the air sack of the neck base could reach its hollow interior, is visible on its side. The third, fourth and fifth vertebrae also show pneumatopores but the consecutive series lacks them, which is surprising as it had been assumed the pneumatisation process would have started at the back, working itself forward. Contrary to what was stated by the 1998 study, the cervical ribs are very elongated, with a length of up to three vertebral centra.

text: The

text: vertebral column

text: of Scipionyx probably includes ten cervical vertebrae and thirteen dorsal vertebrae; due to the fact the specimen is just a hatchling, the differentiation between the two categories has not fully developed, making any distinction rather arbitrary. With certainty five sacral vertebrae are present. The fossil has preserved just nine tail vertebrae; likely fifty or more had been originally present. The neck vertebrae are

text: opisthocoelous

text: . The

text: axis

text: is

text: pneumatised

text: as a pneumatopore, an opening through which a diverticulum of the

text: air sack

text: of the neck base could reach its hollow interior, is visible on its side. The third, fourth and fifth vertebrae also show pneumatopores but the consecutive series lacks them, which is surprising as it had been assumed the pneumatisation process would have started at the back, working itself forward. Contrary to what was stated by the 1998 study, the cervical ribs are very elongated, with a length of up to three vertebral centra.

text: Like all Plasmodium species P. marginatum has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. marginatum has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: Some ectotherms, including several species of fish and reptiles, have been shown to make use of regional endothermy, where muscle activity causes certain parts of the body to remain at higher temperatures than the rest of the body. This allows for better locomotion and use of the senses in cold environments.

text: Some

text: ectotherms

text: , including several species of

text: fish

text: and

text: reptiles

text: , have been shown to make use of regional endothermy, where muscle activity causes certain parts of the body to remain at higher temperatures than the rest of the body. This allows for better locomotion and use of the senses in cold environments.

text: In 1942 he was sent with the rank of Lieutenant Colonel to defend the Italian trenches during World War II in the Africa Campaign on the El Alamein front, recruited by the Military Intelligence commanded by the Major Paolo Caccia Dominioni. During a battle he had a lucky landing in the Sahara Desert with his Fiat Cicogna, that brought him till the last days of the life several damns to the vertebral column.

text: In 1942 he was sent with the rank of Lieutenant Colonel to defend the Italian trenches during

text: World War II

text: in the Africa Campaign on the

text: El Alamein

text: front, recruited by the

text: Military Intelligence

text: commanded by the Major

text: Paolo Caccia Dominioni

text: . During a battle he had a lucky landing in the Sahara Desert with his Fiat Cicogna, that brought him till the last days of the life several damns to the vertebral column.

text: Sediments at the site were originally deposited in lakes or rivers, and carbonates found there contain low carbon isotope ratios. This information suggests that the environment of the Middle Awash was wet during the late Miocene, and that this currently arid region was occupied then by woodland or grassy woodland habitats. Fossil remains of other vertebrates found with the hominins, including the cane rat, further suggest such an environment. The region was the site of periodic volcanism, which probably created distinct ecological regions inhabited by different species of vertebrate animals.

text: Sediment

text: s at the site were originally

text: deposited

text: in lakes or rivers, and

text: carbonate

text: s found there contain low

text: carbon isotope

text: ratios. This information suggests that the environment of the Middle Awash was wet during the late Miocene, and that this currently arid region was occupied then by

text: woodland

text: or grassy woodland habitats. Fossil remains of other

text: vertebrate

text: s found with the hominins, including the

text: cane rat

text: , further suggest such an environment. The region was the site of periodic

text: volcanism

text: , which probably created distinct

text: ecological

text: regions inhabited by different species of vertebrate animals.

text: The evolution of different feeding strategies is varied with some feeding strategies evolving several times in independent lineages. In terrestrial vertebrates, the earliest forms were large amphibious piscivores 400 million years ago. While amphibians continued to feed on fish and later insects, reptiles began exploring two new food types, other tetrapods (carnivory), and later, plants (herbivory). Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation (in contrast, a complex set of adaptations was necessary for feeding on highly fibrous plant materials).

text: The evolution of different feeding strategies is varied with some feeding strategies evolving several times in independent lineages. In terrestrial vertebrates, the earliest forms were large amphibious

text: piscivore

text: s 400 million years ago. While amphibians continued to feed on fish and later insects, reptiles began exploring two new food types, other tetrapods (carnivory), and later, plants (herbivory). Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation (in contrast, a complex set of adaptations was necessary for feeding on highly fibrous plant materials).

text: Just as one can easily analyze how a linear combination of eigenfunctions evolves under application of an operator (because, with respect to these functions, the operator is diagonalized), one can easily analyze how a convex combination of conjugate priors evolves under conditioning; this is called using a hyperprior, and corresponds to using a mixture density of conjugate priors, rather than a single conjugate prior.

text: Just as one can easily analyze how a linear combination of eigenfunctions evolves under application of an operator (because, with respect to these functions, the operator is

text: diagonalized

text: ), one can easily analyze how a convex combination of conjugate priors evolves under conditioning; this is called using a

text: hyperprior

text: , and corresponds to using a

text: mixture density

text: of conjugate priors, rather than a single conjugate prior.

text: Vertebral fixation (also known as "spinal fixation") is a neurosurgical procedure in which two or more vertebrae are anchored to each other through a synthetic "vertebral fixation device", with the aim of reducing vertebral mobility and thus avoiding possible damage to the spinal cord and/or spinal roots.

text: Vertebral fixation (also known as "spinal fixation") is a

text: neurosurgical

text: procedure in which two or more

text: vertebra

text: e are anchored to each other through a synthetic "vertebral fixation device", with the aim of reducing vertebral mobility and thus avoiding possible damage to the

text: spinal cord

text: and/or

text: spinal roots

text: The basic configuration of a vertebra varies; the large part is the body, and the central part is the centrum. The upper and lower surfaces of the vertebra body give attachment to the intervertebral discs. The posterior part of a vertebra forms a vertebral arch, in eleven parts, consisting of two pedicles, two laminae, and seven processes. The laminae give attachment to the ligamenta flava (ligaments of the spine). There are vertebral notches formed from the shape of the pedicles, which form the intervertebral foramina when the vertebrae articulate. These foramina are the entry and exit conducts for the spinal nerves. The body of the vertebra and the vertebral arch form the vertebral foramen, the larger, central opening that accommodates the spinal canal, which encloses and protects the spinal cord.

text: The basic configuration of a vertebra varies; the large part is the body, and the central part is the centrum. The upper and lower surfaces of the vertebra body give attachment to the

text: intervertebral disc

text: s. The posterior part of a vertebra forms a vertebral arch, in eleven parts, consisting of two pedicles, two laminae, and seven

text: processes

text: . The laminae give attachment to the

text: ligamenta flava

text: (ligaments of the spine). There are vertebral notches formed from the shape of the pedicles, which form the

text: intervertebral foramina

text: when the vertebrae

text: articulate

text: . These foramina are the entry and exit conducts for the

text: spinal nerve

text: s. The body of the vertebra and the vertebral arch form the vertebral foramen, the larger, central opening that accommodates the

text: spinal canal

text: , which encloses and protects the

text: spinal cord

text: It functions to prevent hyperflexion of the vertebral column.

text: This complex primitive pattern has, however, been simplified to various degrees in the great majority of vertebrates, as bones have either fused or vanished entirely. In teleosts, only the dentary, articular, and angular bones remain. Cartilagenous fish, such as sharks, do not have any of the bones found in the lower jaw of other vertebrates. Instead, their lower jaw is composed of a cartilagenous structure homologous with the Meckel's cartilage of other groups. This also remains a significant element of the jaw in some primitive bony fish, such as sturgeons.

text: This complex primitive pattern has, however, been simplified to various degrees in the great majority of vertebrates, as bones have either fused or vanished entirely. In

text: teleost

text: s, only the dentary, articular, and

text: angular

text: bones remain.

text: Cartilagenous fish

text: , such as

text: shark

text: cartilage

text: nous structure homologous with the

text: Meckel's cartilage

text: sturgeon

text: s.

text: Jawless fishes belong to the superclass Agnatha in the phylum Chordata, subphylum Vertebrata. Agnatha comes from the Greek, and means "no jaws". It excludes all vertebrates with jaws, known as gnathostomes. Although a minor element of modern marine fauna, jawless fish were prominent among the early fish in the early Paleozoic. Two types of Early Cambrian animal apparently having fins, vertebrate musculature, and gills are known from the early Cambrian Maotianshan shales of China: Haikouichthys and Myllokunmingia. They have been tentatively assigned to Agnatha by Janvier. A third possible agnathid from the same region is Haikouella. A possible agnathid that has not been formally described was reported by Simonetti from the Middle Cambrian Burgess Shale of British Columbia.

text: Jawless fishes belong to the

text: superclass

text: Agnatha

text: in the

text: phylum

text: Chordata

text: , subphylum

text: Vertebrata

text: . Agnatha comes from the

text: Greek

text: , and means "no jaws". It excludes all vertebrates with jaws, known as

text: gnathostome

text: s. Although a minor element of modern marine

text: fauna

text: , jawless fish were prominent among the early fish in the early

text: Paleozoic

text: . Two types of

text: Early Cambrian

text: animal apparently having fins,

text: vertebrate

text: musculature, and gills are known from the early Cambrian

text: Maotianshan shales

text: of

text: China

text: Haikouichthys

text: and

text: Myllokunmingia

text: . They have been tentatively assigned to Agnatha by Janvier. A third possible agnathid from the same region is

text: Haikouella

text: . A possible agnathid that has not been formally described was reported by Simonetti from the Middle Cambrian

text: Burgess Shale

text: of

text: British Columbia

text: Carl H. Eigenmann an ichthyologist wrote Cave vertebrates of America: a study in degenerative evolution (1909) in which he concluded that cave evolution was essentially degenerative. The entomologist William Morton Wheeler and the Lamarckian Ernest MacBride (1866–1940) also advocated degenerative evolution. According to Macbride invertebrates were actually degenerate vertebrates, his argument was based on the idea that "crawling on the seabed was inherently less stimulating than swimming in open waters."

text: Carl H. Eigenmann

text: an

text: ichthyologist

text: wrote Cave vertebrates of America: a study in degenerative evolution (1909) in which he concluded that

text: cave

text: evolution

text: was essentially degenerative. The

text: entomologist

text: William Morton Wheeler

text: and the

text: Lamarckian

text: Ernest MacBride

text: (1866–1940) also advocated degenerative evolution. According to Macbride

text: invertebrate

text: s were actually degenerate

text: vertebrate

text: s, his argument was based on the idea that "crawling on the seabed was inherently less stimulating than swimming in open waters."

text: Like all Plasmodium species P. arachniformis has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. arachniformis has both

text: vertebrate

text: and

text: insect

text: hosts. The

text: vertebrate

text: hosts for this parasite are

text: reptile

text: s.

text: In 1867, physician Theophilus Turner near Fort Wallace in Kansas uncovered a plesiosaur skeleton, which he donated to Cope. Cope attempted to reconstruct the animal on the assumption that the longer extremity of the vertebral column was the tail, the shorter one the neck. He soon noticed that the skeleton taking shape under his hands had some very special qualities: the neck vertebrae had chevrons and with the tail vertebrae the joint surfaces were orientated back to front. Excited, Cope concluded to have discovered an entirely new group of reptiles: the Streptosauria or "Turned Saurians", which would be distinguished by reversed vertebrae and a lack of hindlimbs, the tail providing the main propulsion. After having published a description of this animal, followed by an illustration in a textbook about reptiles and amphibians, Cope invited Marsh and Joseph Leidy to admire his new Elasmosaurus platyurus. Having listened to Cope's interpretation for a while, Marsh suggested that a simpler explanation of the strange build would be that Cope had reversed the vertebral column relative to the body as a whole. When Cope reacted indignantly to this suggestion, Leidy silently took the skull and placed it against the presumed last tail vertebra, to which it fitted perfectly: it was in fact the first neck vertebra, with still a piece of the rear skull attached to it. Mortified, Cope tried to destroy the entire edition of the textbook and, when this failed, immediately published an improved edition with a correct illustration but an identical date of publication. He excused his mistake by claiming that he had been misled by Leidy himself, who, describing a specimen of Cimoliasaurus, had also reversed the vertebral column. Marsh later claimed that the affair was the cause of his rivalry with Cope: "he has since been my bitter enemy". Both Cope and Marsh in their rivalry named many plesiosaur genera and species, most of which are today considered invalid.

text: In 1867, physician Theophilus Turner near

text: Fort Wallace

text: in

text: Kansas

text: uncovered a plesiosaur skeleton, which he donated to Cope. Cope attempted to reconstruct the animal on the assumption that the longer extremity of the vertebral column was the tail, the shorter one the neck. He soon noticed that the skeleton taking shape under his hands had some very special qualities: the neck vertebrae had chevrons and with the tail vertebrae the joint surfaces were orientated back to front. Excited, Cope concluded to have discovered an entirely new group of reptiles: the

text: Streptosauria

text: or "Turned Saurians", which would be distinguished by reversed vertebrae and a lack of hindlimbs, the tail providing the main propulsion. After having published a description of this animal, followed by an illustration in a textbook about reptiles and amphibians, Cope invited Marsh and

text: Joseph Leidy

text: to admire his new

text: Elasmosaurus

text: platyurus. Having listened to Cope's interpretation for a while, Marsh suggested that a simpler explanation of the strange build would be that Cope had reversed the vertebral column relative to the body as a whole. When Cope reacted indignantly to this suggestion, Leidy silently took the skull and placed it against the presumed last tail vertebra, to which it fitted perfectly: it was in fact the first neck vertebra, with still a piece of the rear skull attached to it. Mortified, Cope tried to destroy the entire edition of the textbook and, when this failed, immediately published an improved edition with a correct illustration but an identical date of publication. He excused his mistake by claiming that he had been misled by Leidy himself, who, describing a specimen of

text: Cimoliasaurus

text: , had also reversed the vertebral column. Marsh later claimed that the affair was the cause of his rivalry with Cope: "he has since been my bitter enemy". Both Cope and Marsh in their rivalry named many plesiosaur genera and species, most of which are today considered invalid.

text: Some species reproduce via parthenogenesis, with young emerging from unfertilized eggs, and males of the species have never even been observed.

text: Some species reproduce via

text: parthenogenesis

text: , with young emerging from unfertilized eggs, and males of the species have never even been observed.

text: Anatomy is the study of the shape and form of the human body. The human body has four limbs (two arms and two legs), a head and a neck which connect to the torso. The body's shape is determined by a strong skeleton made of bone and cartilage, surrounded by fat, muscle, connective tissue, organs, and other structures. The spine at the back of the skeleton contains the flexible vertebral column which surrounds the spinal cord, which is a collection of nerve fibres connecting the brain to the rest of the body. Nerves connect the spinal cord and brain to the rest of the body. All major bones, muscles and nerves in the body are named, with the exception of anatomical variations such as sesamoid bones and accessory muscles.

text: Anatomy

text: is the study of the shape and form of the human body. The human body has four

text: limb

text: s (two

text: arm

text: s and two

text: leg

text: s), a

text: head

text: and a

text: neck

text: which connect to the

text: torso

text: . The body's shape is determined by a strong

text: skeleton

text: made of

text: bone

text: and

text: cartilage

text: , surrounded by fat, muscle, connective tissue, organs, and other structures. The

text: spine

text: at the back of the skeleton contains the flexible

text: vertebral column

text: which surrounds the

text: spinal cord

text: , which is a collection of nerve fibres connecting the

text: brain

text: to the rest of the body.

text: Nerve

text: s connect the spinal cord and brain to the rest of the body. All major bones, muscles and nerves in the body are named, with the exception of

text: anatomical variation

text: s such as

text: sesamoid bone

text: s and

text: accessory muscle

text: s.

text: The pedicles are directed backward and slightly upward, and the inferior vertebral notches are of large size, and deeper than in any other region of the vertebral column.

text: The

text: pedicles

text: are directed backward and slightly upward, and the inferior vertebral notches are of large size, and deeper than in any other region of the vertebral column.

text: Facultative endothermy can also be seen in multiple snake species that use their metabolic heat to warm their eggs. Python molurus and Morelia spilota are two python species where females surround their eggs and shiver in order to incubate them.

text: In 2016 a morphological study showed that Tullimonstrum was in fact a basal vertebrate, and thus a member of the phylum Chordata, closely related to modern lampreys. This affinity was attributed based on pronounced cartilaginous arcualia, a dorsal fin and asymmetric caudal fin, keratinous teeth, a single nostril, and tectal cartilages like in lampreys. McCoy et al. raise the possibility that Tullimonstrum belongs to the ancestral group of lamprey, but it also has many features not found in Cyclostomes (lampreys + hagfishes) and thus its exact phylogenetic position is still controversial. Researchers at the University of Leicester found further evidence that Tullimonstrum was a vertebrate: two types of melanosomes in the creature's eyes, a feature found only in vertebrates.

text: In 2016 a morphological study showed that Tullimonstrum was in fact a

text: basal

text: vertebrate

text: , and thus a member of the phylum

text: Chordata

text: , closely related to modern

text: lamprey

text: s. This affinity was attributed based on pronounced cartilaginous arcualia, a

text: dorsal fin

text: and asymmetric

text: caudal fin

text: keratinous

text: teeth, a single nostril, and

text: tectal

text: cartilages like in lampreys. McCoy et al. raise the possibility that Tullimonstrum belongs to the ancestral group of

text: lamprey

text: , but it also has many features not found in

text: Cyclostome

text: s (lampreys +

text: hagfish

text: es) and thus its exact phylogenetic position is still controversial. Researchers at the University of Leicester found further evidence that Tullimonstrum was a vertebrate: two types of

text: melanosome

text: s in the creature's eyes, a feature found only in vertebrates.

text: While normally considered more basal than Ichthyostega, it is possible that Acanthostega was actually more derived. Since Acanthostega resembles juvenile Ichthyostega and shows a lot less differences from juveniles to adults than the latter, it has been suggested that Acanthostega might be descended from a neotenic lineage. Although it appears to have spent its whole life in water, its humerus also exhibits traits that resemble those of later, fully terrestrial stem-tetrapods (the humerus in Ichthyostega is more similar to earlier fishes). This could indicate that vertebrates evolved terrestrial traits earlier than previously assumed, and numerous times independently from another.

text: While normally considered more

text: basal

text: than

text: Ichthyostega

text: , it is possible that Acanthostega was actually more derived. Since Acanthostega resembles juvenile Ichthyostega and shows a lot less differences from juveniles to adults than the latter, it has been suggested that Acanthostega might be descended from a

text: neotenic

text: lineage. Although it appears to have spent its whole life in water, its humerus also exhibits traits that resemble those of later, fully terrestrial stem-tetrapods (the humerus in Ichthyostega is more similar to earlier fishes). This could indicate that vertebrates evolved terrestrial traits earlier than previously assumed, and numerous times independently from another.

text: Limbs in vertebrates are occasionally organized into stylopod (relating to the humerus and femur), zeugopod (relating to the radius and tibia, along with associated structures) and autopod (relating to digits) categories, although anatomically, the evolutionary differences between these groups in early tetrapods tends to be vague.	The transition from fins to limbs occurred once an endoskeleton entered the base of the fin, as seen in today's lungfish. This is thought to have originated in the group Sarcopterygians, including osteolipiforms like Eusthenopteron, due to the homology of the tetrapod forelimb and the osteolepiform fin endoskeleton.

text: Limbs in vertebrates are occasionally organized into stylopod (relating to the humerus and femur), zeugopod (relating to the radius and tibia, along with associated structures) and autopod (relating to digits) categories, although anatomically, the evolutionary differences between these groups in early tetrapods tends to be vague.	The transition from fins to limbs occurred once an endoskeleton entered the base of the fin, as seen in today's lungfish. This is thought to have originated in the group

text: Sarcopterygians

text: , including osteolipiforms like Eusthenopteron, due to the homology of the tetrapod forelimb and the osteolepiform fin endoskeleton.

text: Teleostomi is an obsolete clade of jawed vertebrates that supposedly includes the tetrapods, bony fish, and the wholly extinct acanthodian fish. Key characters of this group include an operculum and a single pair of respiratory openings, features which were lost or modified in some later representatives.  The teleostomes include all jawed vertebrates except the chondrichthyans and the extinct class Placodermi.

text: Teleostomi is an obsolete

text: clade

text: of

text: jawed vertebrates

text: that supposedly includes the

text: tetrapod

text: s,

text: bony fish

text: , and the wholly extinct

text: acanthodian

text: fish. Key characters of this group include an

text: operculum

text: and a single pair of respiratory openings, features which were lost or modified in some later representatives.  The teleostomes include all jawed vertebrates except the

text: chondrichthyans

text: and the

text: extinct

text: class

text: Placodermi

text: Oligokyphus lived beneath the feet of dinosaurs, such as the theropods Dilophosaurus, Kayentavenator  Megapnosaurus kayentakatae, the "Shake N Bake" theropod, the basal sauropodomorph Sarahsaurus,heterodontosaurids, and the armored dinosaurs Scelidosaurus and Scutellosaurus.  The Kayenta Formation has produced that remains of three coelophysoid taxa of different body size, which represents the most diverse ceratosaur fauna yet known.  The Kayenta Formation has yielded a small but growing assemblage of organisms.  Vertebrates present here at the time of Oligokyphus included hybodont sharks, bony fish known as osteichthyes, lungfish, salamanders, the frog Prosalirus, the caecilian Eocaecilia, the turtle Kayentachelys, a sphenodontian reptile, various lizards.  Also present were the synapsids Dinnebiton and Kayentatherium, several early crocodylomorphs including Calsoyasuchus, Eopneumatosuchus, Kayentasuchus, and Protosuchus), and the pterosaur Rhamphinion.	The possible presence of the early true mammal Dinnetherium, and a haramyid mammal has also been proposed, based on fossil finds.  Vertebrate trace fossils from this area included coprolites and the tracks of therapsids, lizard-like animals, and dinosaurs, which provided evidence that these animals were also present.  Non-vertebrates in this ecosystem included microbial or "algal" limestone, freshwater bivalves, freshwater mussels and snails, and ostracods.  The plant life known from this area included trees that became preserved as petrified wood.

text: Oligokyphus lived beneath the feet of dinosaurs, such as the theropods Dilophosaurus,

text: Kayentavenator

text: Megapnosaurus kayentakatae

text: , the "Shake N Bake" theropod, the

text: basal

text: sauropodomorph

text: Sarahsaurus

text: heterodontosaurids

text: , and the armored dinosaurs

text: Scelidosaurus

text: and

text: Scutellosaurus

text: .  The Kayenta Formation has produced that remains of three coelophysoid taxa of different body size, which represents the most diverse ceratosaur fauna yet known.  The Kayenta Formation has yielded a small but growing assemblage of organisms.  Vertebrates present here at the time of Oligokyphus included

text: hybodont

text: sharks,

text: bony fish

text: known as osteichthyes,

text: lungfish

text: , salamanders, the frog

text: Prosalirus

text: , the

text: caecilia

text: n

text: Eocaecilia

text: , the turtle

text: Kayentachelys

text: , a

text: sphenodontia

text: n reptile, various lizards.  Also present were the

text: synapsids

text: Dinnebiton and

text: Kayentatherium

text: , several early

text: crocodylomorphs

text: including

text: Calsoyasuchus

text: Eopneumatosuchus

text: Kayentasuchus

text: , and

text: Protosuchus

text: ), and the

text: pterosaur

text: Rhamphinion

text: .	The possible presence of the early true mammal

text: Dinnetherium

text: , and a

text: haramyid

text: mammal has also been proposed, based on fossil finds.  Vertebrate trace fossils from this area included

text: coprolite

text: s and the tracks of

text: therapsid

text: s, lizard-like animals, and dinosaurs, which provided evidence that these animals were also present.  Non-vertebrates in this ecosystem included microbial or "algal" limestone, freshwater bivalves, freshwater mussels and snails, and

text: ostracod

text: s.  The plant life known from this area included trees that became preserved as petrified wood.

text: In air-breathing vertebrates, cartilage is replaced by cellular bone. A transitional tissue is mineralized cartilage. Cartilage mineralizes by massive expression of phosphate-producing enzymes, which cause high local concentrations of calcium and phosphate that precipitate. This mineralized cartilage is not dense or strong. In the air breathing vertebrates it is used as a scaffold for formation of cellular bone made by osteoblasts, and then it is removed by osteoclasts, which specialize in degrading mineralized tissue.

text: In air-breathing vertebrates, cartilage is replaced by cellular bone. A transitional tissue is mineralized

text: cartilage

text: . Cartilage mineralizes by massive expression of phosphate-producing enzymes, which cause high local concentrations of calcium and phosphate that precipitate. This mineralized cartilage is not dense or strong. In the air breathing vertebrates it is used as a scaffold for formation of cellular bone made by osteoblasts, and then it is removed by

text: osteoclasts

text: , which specialize in degrading mineralized tissue.

text: Several hypotheses have been proposed for how bone evolved as a structural element in vertebrates. One hypothesis is that bone developed from tissues that evolved to store minerals. Specifically, calcium-based minerals were stored in cartilage and bone was an exaptation development from this calcified cartilage. However, other possibilities include bony tissue evolving as an osmotic barrier, or as a protective structure.

text: Several hypotheses have been proposed for how bone evolved as a structural element in

text: vertebrates

text: . One hypothesis is that bone developed from tissues that evolved to store

text: mineral

text: s. Specifically, calcium-based minerals were stored in cartilage and bone was an

text: exaptation

text: development from this calcified cartilage. However, other possibilities include bony tissue evolving as an

text: osmotic barrier

text: , or as a protective structure.

text: There has been long debate as to why there are so few fossils from this time period. Some have suggested the problem was of fossilization itself, suggesting that there may have been differences in the geochemistry of the time that did not favour fossil formation. Also, excavators simply may not have dug in the right places. However, the existence of a true low point in vertebrate diversity has been supported by independent lines of evidence.

text: There has been long debate as to why there are so few fossils from this time period. Some have suggested the problem was of

text: fossilization

text: itself, suggesting that there may have been differences in the geochemistry of the time that did not favour fossil formation. Also, excavators simply may not have dug in the right places. However, the existence of a true low point in vertebrate diversity has been supported by independent lines of evidence.

text: In cartilage, the lacunae and hence, the chondrocytes, are isolated from each other.  Materials picked up by osteocytes adjacent to blood vessels are distributed throughout the bone matrix via the canaliculi.

text: In

text: cartilage

text: , the lacunae and hence, the

text: chondrocytes

text: , are isolated from each other.  Materials picked up by osteocytes adjacent to blood vessels are distributed throughout the bone matrix via the canaliculi.

text: The circulatory systems of all vertebrates, as well as of annelids (for example, earthworms) and cephalopods (squids, octopuses and relatives) are closed, just as in humans. Still, the systems of fish, amphibians, reptiles, and birds show various stages of the evolution of the circulatory system.

text: The circulatory systems of all

text: vertebrate

text: s, as well as of

text: annelid

text: s (for example,

text: earthworm

text: s) and

text: cephalopod

text: s (

text: squid

text: s,

text: octopus

text: es and relatives) are closed, just as in humans. Still, the systems of

text: fish

text: amphibian

text: s,

text: reptile

text: s, and

text: bird

text: s show various stages of the

text: evolution

text: of the circulatory system.

text: From the ninth cervical vertebra to the back, the vertebral joints show the remains of articular capsules. Between the spines at places very thin interspinal and supraspinal ligaments are visible. Six vertebrae are visibly capped by cartilaginous synchondroses, a typical juvenile feature. Cartilaginous caps are also present on all limb joints, even the smallest, and are especially thick in the shoulder, elbow and wrist joints. Also the pubic foot is capped and the ilium and pubic bone are separated by cartilage.

text: From the ninth cervical vertebra to the back, the vertebral joints show the remains of

text: articular capsule

text: s. Between the spines at places very thin interspinal and supraspinal

text: ligaments

text: are visible. Six vertebrae are visibly capped by cartilaginous synchondroses, a typical juvenile feature. Cartilaginous caps are also present on all limb joints, even the smallest, and are especially thick in the shoulder, elbow and wrist joints. Also the pubic foot is capped and the ilium and pubic bone are separated by cartilage.

text: The pharyngula is a stage in the embryonic development of vertebrates. At this stage, the embryos of all vertebrates are similar, having developed features typical of vertebrates, such as the beginning of a spinal cord. Named by William Ballard, the pharyngula stage follows the blastula, gastrula and neurula stages.

text: The pharyngula is a stage in the

text: embryo

text: nic development of vertebrates. At this stage, the embryos of all vertebrates are similar, having developed features typical of vertebrates, such as the beginning of a spinal cord. Named by

text: William Ballard

text: , the pharyngula stage follows the

text: blastula

text: gastrula

text: and

text: neurula

text: stages.

text: Many ectotherms exploit the heat produced by endotherms by sharing their nests and burrows. For example, mammal burrows are used by geckos and seabird burrows by Australian tiger snakes  and New Zealand tuatara   Termites create in their mounds high and regulated temperatures and this is exploited by some species of lizards, snakes and crocodiles.

text: Many ectotherms exploit the heat produced by endotherms by sharing their

text: nest

text: s and

text: burrow

text: s. For example, mammal burrows are used by

text: gecko

text: s and seabird burrows by Australian

text: tiger snake

text: s  and New Zealand

text: tuatara

text: Termite

text: s create in their mounds high and regulated temperatures and this is exploited by some species of lizards, snakes and crocodiles.

text: Bony fish include the lobe-finned fish and the ray finned fish. The lobe-finned fish is the class of fleshy finned fishes, consisting of lungfish, and coelacanths. They are bony fish with fleshy, lobed paired fins, which are joined to the body by a single bone. These fins evolved into the legs of the first tetrapod land vertebrates, amphibians. Ray finned fishes are so-called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines ("rays").

text: Bony fish

text: include the

text: lobe-finned fish

text: and the

text: ray finned fish

text: . The lobe-finned fish is the

text: class

text: of fleshy finned fishes, consisting of

text: lungfish

text: , and

text: coelacanth

text: s. They are bony fish with fleshy, lobed paired fins, which are joined to the body by a single bone. These fins evolved into the legs of the first

text: tetrapod

text: land

text: vertebrates

text: amphibian

text: s. Ray finned fishes are so-called because they possess

text: lepidotrichia

text: or "fin rays", their fins being webs of skin supported by bony or horny spines ("rays").

text: The spinal cord is divided into 31 segments, located between the vertebrae. Each segment is defined by a posterior root entering it and an anterior root exiting it. Each of these roots is the end of a spinal nerve connecting the spinal cord to the body. The vertebral column is divided into four groups of vertebrae: (from top to bottom) cervical, thoracic, lumbar, and sacral.

text: The

text: spinal cord

text: is divided into 31 segments, located between the

text: vertebrae

text: . Each segment is defined by a

text: posterior root

text: entering it and an

text: anterior root

text: exiting it. Each of these roots is the end of a spinal nerve connecting the spinal cord to the body. The

text: vertebral column

text: is divided into four groups of vertebrae: (from top to bottom)

text: cervical

text: thoracic

text: lumbar

text: , and

text: sacral

text: It is difficult to estimate the rate of eye evolution because the fossil record, particularly of the Early Cambrian, is poor. The evolution of a circular patch of photoreceptor cells into a fully functional vertebrate eye has been approximated based on rates of mutation, relative advantage to the organism, and natural selection. Based on pessimistic calculations that consistently overestimate the time required for each stage and a generation time of one year, which is common in small animals, it has been proposed that it would take less than 364,000 years for the vertebrate eye to evolve from a patch of photoreceptors.

text: For obvious reasons, any problem with the backbone of a vertebrate is often considered a potential disability which can limit a person's ability to manoeuvre their way around their surroundings, cause a lot of pain and be responsible for mental distress. This has been researched upon by Lichun Lu and Xifeng Lu, scientists from Mayo Clinic’s college of medicine, who have developed a novel spinal graft that, once surgically placed in the body, will grow to be just the right size and shape to fix the spinal column. They presented their work at the 251st National Meeting & Exposition of the non-profit organization American Chemical Society (ACS).

text: For obvious reasons, any problem with the

text: backbone

text: of a

text: vertebrate

text: is often considered a potential disability which can limit a person's ability to manoeuvre their way around their surroundings, cause a lot of

text: pain

text: and be responsible for

text: mental distress

text: . This has been researched upon by Lichun Lu and Xifeng Lu, scientists from Mayo Clinic’s college of medicine, who have developed a novel spinal graft that, once

text: surgically

text: placed in the body, will grow to be just the right size and shape to fix the spinal column. They presented their work at the 251st National Meeting & Exposition of the non-profit organization American Chemical Society (ACS).

text: Most life forms evolved initially in marine habitats. Oceans provide about 99 percent of the living space on the planet. The earliest vertebrates appeared in the form of fish, which live exclusively in water. Some of these evolved into amphibians which spend portions of their lives in water and portions on land. Other fish evolved into land mammals and subsequently returned to the ocean as seals, dolphins or whales. Plant forms such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton is generally the foundation of the ocean food chain.

text: Most life forms evolved initially in

text: marine habitats

text: . Oceans provide about 99 percent of the living space on the planet. The earliest

text: vertebrate

text: s appeared in the form of

text: fish

text: , which live exclusively in water. Some of these evolved into

text: amphibian

text: s which spend portions of their lives in water and portions on land. Other fish evolved into land mammals and subsequently returned to the ocean as

text: seals

text: dolphin

text: s or

text: whale

text: s. Plant forms such as

text: kelp

text: and

text: algae

text: grow in the water and are the basis for some underwater ecosystems.

text: Plankton

text: is generally the foundation of the ocean

text: food chain

text: Many animals that live in water use external fertilization, whereas internal fertilization may have developed from a need to maintain gametes in a liquid medium in the Late Ordovician epoch. Internal fertilization with many vertebrates (such as reptiles, some fish, and most birds) occur via cloacal copulation (see also hemipenis), while mammals copulate vaginally, and many basal vertebrates reproduce sexually with external fertilization.

text: Many animals that live in water use

text: external fertilization

text: , whereas

text: internal fertilization

text: may have developed from a need to maintain

text: gamete

text: s in a liquid medium in the

text: Late Ordovician

text: epoch. Internal fertilization with many vertebrates (such as

text: reptile

text: s, some

text: fish

text: , and most

text: bird

text: s) occur via

text: cloaca

text: l copulation (see also

text: hemipenis

text: ), while

text: mammal

text: s copulate vaginally, and many

text: basal

text: vertebrate

text: s reproduce sexually with external fertilization.

text: Diadectidae is an extinct family of early tetrapods that lived in what is now North America and Europe during the Late Carboniferous and Early Permian, and in Asia during the Late Permian. They were the first herbivorous tetrapods, and also the first fully terrestrial animals to attain large sizes. Footprints indicate that diadectids walked with an erect posture. They were the first to exploit plant material in terrestrial food chains, making their appearance an important stage in both vertebrate evolution and the development of terrestrial ecosystems.

text: Diadectidae is an extinct

text: family

text: of early

text: tetrapod

text: s that lived in what is now

text: North America

text: and

text: Europe

text: during the

text: Late Carboniferous

text: and

text: Early Permian

text: , and in

text: Asia

text: during the

text: Late Permian

text: . They were the first

text: herbivorous

text: tetrapod

text: s, and also the first fully terrestrial animals to attain large sizes. Footprints indicate that diadectids walked with an erect posture. They were the first to exploit plant material in terrestrial food chains, making their appearance an important stage in both vertebrate evolution and the development of terrestrial

text: ecosystem

text: s.

text: Up until now, scientists assumed that the last common ancestor of jawed vertebrates was a shark-like animal, with no distinct jawbones, and that modern jaws evolved in early bony fishes. This discovery shows that modern jaws evolved earlier. It is possible that Chondrichthyes started with distinct jaws and then dispensed with them. This has been called the earliest known animal with what looks like a face.

text: The provision of care, by either males or females, is presumed to increase growth rates, quality, and/or survival of young, and hence ultimately increase the inclusive fitness of parents. In a variety of vertebrate species (e.g., about 80% of birds and about 6% of mammals), both males and females invest heavily in their offspring. Many of these biparental species are socially monogamous, so individuals remain with their mate for at least one breeding season.	Exclusive paternal care has evolved multiple times in a variety of organisms, including invertebrates, fishes, and amphibians.

text: The provision of care, by either males or females, is presumed to increase growth rates, quality, and/or survival of young, and hence ultimately increase the

text: inclusive fitness

text: of parents. In a variety of vertebrate species (e.g., about 80% of birds and about 6% of mammals), both males and females invest heavily in their offspring. Many of these biparental species are socially

text: monogamous

text: , so individuals remain with their mate for at least one breeding season.	Exclusive paternal care has evolved multiple times in a variety of organisms, including invertebrates, fishes, and amphibians.

text: Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue. Bones have a variety of shapes with a complex internal and external structure they are also lightweight, yet strong and hard. One of the types of tissue that makes up bone tissue is mineralized tissue and this gives it rigidity and a honeycomb-like three-dimensional internal structure. Other types of tissue found in bones include marrow, endosteum and periosteum, nerves, blood vessels and cartilage. There are 206 bones in the adult human body and 270 in an infant.

text: Bones are rigid

text: organs

text: that form part of the

text: endoskeleton

text: of

text: vertebrate

text: s. They function to move, support, and protect the various organs of the body, produce

text: red

text: and

text: white blood cell

text: s and store

text: mineral

text: s. Bone tissue is a type of dense

text: connective tissue

text: . Bones have a variety of shapes with a complex internal and external

text: structure

text: they are also lightweight, yet strong and hard. One of the types of tissue that makes up bone tissue is

text: mineralized tissue

text: and this gives it rigidity and a

text: honeycomb-like

text: three-dimensional internal structure. Other types of tissue found in bones include

text: marrow

text: endosteum

text: and

text: periosteum

text: nerve

text: s,

text: blood vessel

text: s and

text: cartilage

text: . There are 206 bones in the adult human body and 270 in an

text: infant

text: The vertebral arteries arise from the subclavian arteries, one on each side of the body, then enter deep to the transverse process at the level of the 6th cervical vertebrae (C6), or occasionally (in 7.5% of cases) at the level of C7.  They then proceed superiorly, in the transverse foramen of each cervical vertebra. Once they have passed through the transverse foramen of C1 (also known as the atlas), the vertebral arteries travel across the posterior arch of C1 and through the suboccipital triangle before entering the foramen magnum.

text: The vertebral arteries arise from the subclavian arteries, one on each side of the body, then enter deep to the transverse process at the level of the 6th

text: cervical vertebrae

text: (C6), or occasionally (in 7.5% of cases) at the level of C7.  They then proceed superiorly, in the

text: transverse foramen

text: of each

text: cervical vertebra

text: . Once they have passed through the transverse foramen of C1 (also known as the

text: atlas

text: ), the vertebral arteries travel across the posterior arch of C1 and through the

text: suboccipital triangle

text: before entering the

text: foramen magnum

text: Swim bladders are evolutionarily closely related (i.e., homologous) to lungs. It is believed that the first lungs, simple sacs connected to the gut that allowed the organism to gulp air under oxygen-poor conditions, evolved into the lungs of today's terrestrial vertebrates and some fish (e.g., lungfish, gar, and bichir) and into the swim bladders of the ray-finned fish. In embryonal development, both lung and swim bladder originate as an outpocketing from the gut; in the case of swim bladders, this connection to the gut continues to exist as the pneumatic duct in the more "primitive" ray-finned fish, and is lost in some of the more derived teleost orders.  There are no animals which have both lungs and a swim bladder.

text: Swim bladders are evolutionarily closely related (i.e.,

text: homologous

text: ) to

text: lung

text: s. It is believed that the first lungs, simple sacs connected to the

text: gut

text: that allowed the organism to gulp air under oxygen-poor conditions, evolved into the lungs of today's terrestrial

text: vertebrate

text: s and some fish (e.g.,

text: lungfish

text: gar

text: , and

text: bichir

text: ) and into the swim bladders of the

text: ray-finned fish

text: . In

text: embryo

text: nal development, both lung and swim bladder originate as an outpocketing from the gut; in the case of swim bladders, this connection to the gut continues to exist as the pneumatic duct in the more "primitive" ray-finned fish, and is lost in some of the more derived

text: teleost

text: orders.  There are no animals which have both lungs and a swim bladder.

text: Ectotherms will increase their body temperature mostly through external heat sources such as sunlight energy, therefore they depend on the occurring environmental conditions to reach operational body temperatures. Endothermic animals mostly use internal heat production through metabolic active organs and tissues (liver, kidney, heart, brain, muscle) or specialized heat producing tissues like brown adipose tissue (BAT). In general, endotherms therefore have higher metabolic rates than ectotherms at a given body mass. As a consequence they would also need higher food intake rates, which may limit abundance of endotherms more than ectotherms.

text: Ectotherms

text: will increase their body temperature mostly through external heat sources such as

text: sunlight

text: energy, therefore they depend on the occurring environmental conditions to reach operational body temperatures. Endothermic animals mostly use internal heat production through metabolic active organs and tissues (liver, kidney, heart, brain, muscle) or specialized heat producing tissues like

text: brown adipose tissue

text: (BAT). In general, endotherms therefore have higher metabolic rates than ectotherms at a given body mass. As a consequence they would also need higher food intake rates, which may limit abundance of endotherms more than ectotherms.

text: Many insect species are able to maintain a thoracic temperature above the ambient temperature using exercise. These are known as facultative or exercise endotherms. The honey bee, for example, does so by contracting antagonistic flight muscles without moving its wings (see insect thermoregulation). This form of thermogenesis is, however, only efficient above a certain temperature threshold, and below about , the honey bee reverts to ectothermy.

text: Many

text: insect

text: species are able to maintain a thoracic temperature above the ambient temperature using exercise. These are known as facultative or exercise endotherms. The

text: honey bee

text: , for example, does so by contracting antagonistic flight muscles without moving its wings (see

text: insect thermoregulation

text: ). This form of thermogenesis is, however, only efficient above a certain temperature threshold, and below about , the honey bee reverts to ectothermy.

text: Mammals and birds typically have a fully erect posture, though each evolved it independently. In these groups the legs are placed beneath the body. This is often linked with the evolution of endothermy, as it avoids Carrier's constraint and thus allows prolonged periods of activity. The fully erect stance is not necessarily the "most-evolved" stance; evidence suggests that crocodilians evolved a semi-erect stance in their forelimbs from ancestors with fully erect stance as a result of adapting to a mostly aquatic lifestyle, though their hindlimbs are still held fully erect.  For example, the mesozoic prehistoric crocodilian Erpetosuchus is believed to have had a fully erect stance and been terrestrial.

text: Mammal

text: s and

text: bird

text: s typically have a fully erect posture, though each evolved it independently. In these groups the legs are placed beneath the body. This is often linked with the evolution of

text: endothermy

text: , as it avoids

text: Carrier's constraint

text: and thus allows prolonged periods of activity. The fully erect stance is not necessarily the "most-evolved" stance; evidence suggests that crocodilians evolved a semi-erect stance in their forelimbs from ancestors with fully erect stance as a result of adapting to a mostly aquatic lifestyle, though their hindlimbs are still held fully erect.  For example, the

text: mesozoic

text: prehistoric crocodilian

text: Erpetosuchus

text: is believed to have had a fully erect stance and been terrestrial.

text: The trait that is common to all invertebrates is the absence of a vertebral column (backbone): this creates a distinction between invertebrates and vertebrates. The distinction is one of convenience only; it is not based on any clear biologically homologous trait, any more than the common trait of having wings functionally unites insects, bats, and birds, or than not having wings unites tortoises, snails and sponges. Being animals, invertebrates are heterotrophs, and require sustenance in the form of the consumption of other organisms. With a few exceptions, such as the Porifera, invertebrates generally have bodies composed of differentiated tissues. There is also typically a digestive chamber with one or two openings to the exterior.

text: The trait that is common to all invertebrates is the absence of a

text: vertebral column

text: (backbone): this creates a distinction between invertebrates and vertebrates. The distinction is one of convenience only; it is not based on any clear biologically

text: homologous

text: trait, any more than the common trait of having wings functionally unites insects, bats, and birds, or than not having wings unites

text: tortoise

text: s,

text: snail

text: s and

text: sponge

text: s. Being animals, invertebrates are heterotrophs, and require sustenance in the form of the consumption of other organisms. With a few exceptions, such as the

text: Porifera

text: , invertebrates generally have bodies composed of differentiated tissues. There is also typically a digestive chamber with one or two openings to the exterior.

text: Diet: feeds on small sharks, bony fishes, cuttlefish, and crustaceans. Reproduction: are ovoviviparous.

text: Diet: feeds on small sharks, bony fishes, cuttlefish, and crustaceans. Reproduction: are

text: ovoviviparous

text: Like all Plasmodium species P. diploglossi has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. diploglossi has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: When the vertebral body has been removed, the surgeon performs a vertebral fusion. Because a space in the column remains from the surgery, it must be filled using a block of bone taken from the pelvis or one of the leg bones or with a manufactured component such as a cage. This bone graft holds the remaining vertebrae apart. As it heals, the vertebrae grow together and fuse.

text: When the vertebral body has been removed, the surgeon performs a

text: vertebral fusion

text: . Because a space in the column remains from the surgery, it must be filled using a block of bone taken from the

text: pelvis

text: or one of the leg bones or with a manufactured component such as a cage. This

text: bone graft

text: holds the remaining vertebrae apart. As it heals, the vertebrae grow together and

text: fuse

text: He was elected a Fellow of the Royal Society in March 1952. The citation on his application read: "Westoll is a palaeontologist who by his description of new materials and by the introduction of new and fertile ideas into the interpretation of the structure of early fossil vertebrates has greatly increased our understanding of the problems they present. He has introduced new views about the origins of the pectoral fins of craniates and of the Tetrapod limb. He has clarified our ideas about the homologies of the dermal skull bones of vertebrates and made a new and convincing comparison between the skulls of Amphibia and Fish. He has made important contributions towards the solution of the old problems of the origin of the mammalian palate and ear. His monograph of the Haplolepidae sets a new standard for taxonomic work on fossil fish".

text: He was elected a

text: Fellow of the Royal Society

text: in March 1952. The citation on his application read: "Westoll is a palaeontologist who by his description of new materials and by the introduction of new and fertile ideas into the interpretation of the structure of early fossil vertebrates has greatly increased our understanding of the problems they present. He has introduced new views about the origins of the pectoral fins of craniates and of the Tetrapod limb. He has clarified our ideas about the homologies of the dermal skull bones of vertebrates and made a new and convincing comparison between the skulls of Amphibia and Fish. He has made important contributions towards the solution of the old problems of the origin of the mammalian palate and ear. His monograph of the Haplolepidae sets a new standard for taxonomic work on fossil fish".

text: Snell has also conducted extensive research on the efficiency of various restoration strategies for Galápagos vertebrates, and how to control, eradicate, and mitigate introduced species of vertebrates. He has also developed effective methods for ecological monitoring and improving responses by management agencies.

text: Snell has also conducted extensive research on the efficiency of various restoration strategies for Galápagos vertebrates, and how to control, eradicate, and mitigate

text: introduced species

text: of vertebrates. He has also developed effective methods for ecological monitoring and improving responses by management agencies.

text: To cut a T-bone from butchered cattle, a lumbar vertebra is sawn in half through the vertebral column. The downward prong of the 'T' is a transverse process of the vertebra, and the flesh surrounding it is the spinal muscles. The small semicircle at the top of the 'T' is half of the vertebral foramen.

text: To cut a T-bone from

text: butchered

text: cattle

text: , a

text: lumbar vertebra

text: is sawn in half through the

text: vertebral column

text: . The downward prong of the 'T' is a

text: transverse process

text: of the

text: vertebra

text: , and the flesh surrounding it is the spinal

text: muscle

text: s. The small semicircle at the top of the 'T' is half of the

text: vertebral foramen

text: Spina bifida is characterized by a midline cleft in the vertebral arch.  It usually causes no symptoms in dogs.  It is seen most commonly in Bulldogs and Manx cats.  In Manx it accompanies a condition known as sacrocaudal dysgenesis that gives these cats their characteristic tailless or stumpy tail appearance.  It is inherited in Manx as an autosomal dominant trait.

text: Spina bifida

text: is characterized by a midline cleft in the vertebral arch.  It usually causes no symptoms in dogs.  It is seen most commonly in Bulldogs and

text: Manx

text: cats.  In Manx it accompanies a condition known as sacrocaudal dysgenesis that gives these cats their characteristic tailless or stumpy tail appearance.  It is inherited in Manx as an

text: autosomal dominant

text: trait.

text: The body energy expenditure of ectothermic animals  is  about 1/13 of that of endotherms  but the energy expenditure of the brains of both ectothermic and endothermic animals are  similar. Other high brain percentage  (2.6–3.7 % of the body mass) animals exist such as  bats, swallows, crows and sparrows but these due to their endothermy also have high body energy metabolism. The unusual high brain energy consumption percentage of mormyrinae fish is thus due to them having the unusual combination of a large brain in a low energy consuming body. The actual energy consumption per unit mass of its brain is not in fact particularly high and indeed lower (2.02 mg g h) than that in some other fish such as  Salmonidae (2.20 mg g h).  In comparison, that of rats is 6.02 mg g h and humans 2.61 mg g h.

text: The body energy expenditure of ectothermic animals  is  about 1/13 of that of endotherms  but the energy expenditure of the brains of both ectothermic and endothermic animals are  similar. Other high brain percentage  (2.6–3.7 % of the body mass) animals exist such as

text: bat

text: s,

text: swallow

text: s,

text: crow

text: s and

text: sparrow

text: s but these due to their endothermy also have high body energy metabolism. The unusual high brain energy consumption percentage of mormyrinae fish is thus due to them having the unusual combination of a large brain in a low energy consuming body. The actual energy consumption per unit mass of its brain is not in fact particularly high and indeed lower (2.02 mg g h) than that in some other fish such as

text: Salmonidae

text: (2.20 mg g h).  In comparison, that of rats is 6.02 mg g h and humans 2.61 mg g h.

text: The character for fish (魚) evolved from an ancient pictograph. It is the traditional 195th (out of 216) traditional radical. Over time, the pictographic representations tended to become increasingly stylized, until evolving to the modern standard form:

text: The character for fish (魚) evolved from an ancient pictograph. It is the traditional 195th (out of 216)

text: traditional radical

text: . Over time, the pictographic representations tended to become increasingly stylized, until evolving to the modern standard form:

text: A neuroendocrine system has been observed in all animals with a nervous system and all vertebrates have an hypothalamus-pituitary axis. All vertebrates have a thyroid, which in amphibians is also crucial for transformation of larvae into adult form. All vertebrates have adrenal gland tissue, with mammals unique in having it organized into layers. All vertebrates have some form of renin-angiotensin axis, and all tetrapods have aldosterone as primary mineralocorticoid.

text: A neuroendocrine system has been observed in all

text: animal

text: s with a nervous system and all

text: vertebrate

text: s have an hypothalamus-pituitary axis. All vertebrates have a thyroid, which in

text: amphibian

text: s is also crucial for transformation of larvae into adult form. All vertebrates have adrenal gland tissue, with mammals unique in having it organized into layers. All vertebrates have some form of renin-angiotensin axis, and all

text: tetrapods

text: have aldosterone as primary

text: mineralocorticoid

text: The appearance of the early vertebrate jaw has been described as "a crucial innovation" and "perhaps the most profound and radical evolutionary step in the vertebrate history". Fish without jaws had more difficulty surviving than fish with jaws, and most jawless fish became extinct. However studies of the cyclostomes, the jawless hagfishes and lampreys that did survive, have yielded little insight into the deep remodelling of the vertebrate skull that must have taken place as early jaws evolved.

text: The appearance of the early vertebrate jaw has been described as "a crucial innovation" and "perhaps the most profound and radical evolutionary step in the vertebrate history".

text: Fish without jaws

text: had more difficulty surviving than fish with jaws, and most jawless fish became extinct. However studies of the

text: cyclostomes

text: , the jawless

text: hagfish

text: es and

text: lamprey

text: s that did survive, have yielded little insight into the deep remodelling of the vertebrate skull that must have taken place as early jaws evolved.

text: Lobe-finned fishes, such as coelacanths and lungfish, were the most diverse group of bony fishes in the Devonian. Taxonomists who subscribe to the cladistic approach include the grouping Tetrapoda within the Sarcopterygii, and the tetrapods in turn include all species of four-limbed vertebrates. The fin-limbs of lobe-finned fishes such as the coelacanths show a strong similarity to the expected ancestral form of tetrapod limbs. The lobe-finned fish apparently followed two different lines of development and are accordingly separated into two subclasses, the Rhipidistia (including the lungfish, and the Tetrapodomorpha, which include the Tetrapoda) and the Actinistia (coelacanths). The first lobe-finned fishes, found in the uppermost Silurian (ca 418 Ma), closely resembled spiny sharks, which became extinct at the end of the Paleozoic. In the early–middle Devonian (416 - 385 Ma), while the predatory placoderms dominated the seas, some lobe-finned fishes came into freshwater habitats.

text: Lobe-finned fishes, such as

text: coelacanth

text: s and

text: lungfish

text: , were the most diverse group of bony fishes in the Devonian. Taxonomists who subscribe to the cladistic approach include the grouping

text: Tetrapoda

text: within the Sarcopterygii, and the tetrapods in turn include all species of four-limbed vertebrates. The fin-limbs of lobe-finned fishes such as the coelacanths show a strong similarity to the expected ancestral form of tetrapod limbs. The lobe-finned fish apparently followed two different lines of development and are accordingly separated into two subclasses, the

text: Rhipidistia

text: (including the lungfish, and the

text: Tetrapodomorpha

text: , which include the Tetrapoda) and the

text: Actinistia

text: (coelacanths). The first lobe-finned fishes, found in the uppermost

text: Silurian

text: (ca 418 Ma), closely resembled

text: spiny shark

text: s, which became extinct at the end of the Paleozoic. In the early–middle

text: Devonian

text: (416 - 385 Ma), while the predatory

text: placoderms

text: dominated the seas, some lobe-finned fishes came into

text: freshwater

text: habitats.

text: Beneath the upper lateral-cartilages lay the lower lateral-cartilages; the paired lower lateral-cartilages swing outwards, from medial attachments, to the caudal septum in the midline (the medial crura) to an intermediate crus (shank) area. Finally, the lower lateral-cartilages flare outwards, above and to the side (superolaterally), as the lateral crura; these cartilages are mobile, unlike the upper lateral cartilages. Furthermore, some persons present anatomical evidence of nasal scrolling — i.e. an outward curving of the lower borders of the upper lateral-cartilages, and an inward curving of the cephalic borders of the alar cartilages.

text: A bone is a rigid organ that constitutes part of the vertebral skeleton. Bones support and protect the various organs of the body, produce red and white blood cells, store minerals and also enable mobility as well as support for the body.  Bone tissue is a type of dense connective tissue. Bones come in a variety of shapes and sizes and have a complex internal and external structure. They are lightweight yet strong and hard, and serve multiple functions. Mineralized osseous tissue, or bone tissue, is of two types, cortical and cancellous, and gives a bone rigidity and a coral-like three-dimensional internal structure. Other types of tissue found in bones include marrow, endosteum, periosteum, nerves, blood vessels and cartilage.

text: A bone is a

text: rigid

text: organ

text: that constitutes part of the

text: vertebral

text: skeleton

text: red

text: and

text: white blood cell

text: s, store

text: mineral

text: s and also enable mobility as well as support for the body.

text: Bone tissue

text: is a type of dense

text: connective tissue

text: structure

text: functions

text: Mineralized

text: osseous tissue, or bone tissue, is of two types,

text: cortical

text: and

text: cancellous

text: , and gives a bone rigidity and a

text: coral

text: marrow

text: endosteum

text: periosteum

text: nerve

text: s,

text: blood vessel

text: s and

text: cartilage

text: Symptoms are mainly promoted in the bone structure. Due to a high fluorine concentration in the body, the bone is hardened and thus less elastic, resulting in an increased frequency of fractures. Other symptoms include thickening of the bone structure and accumulation of bone tissue, which both contribute to impaired joint mobility. Ligaments and cartilage can become ossified. Most patients suffering from skeletal fluorosis show side effects from the high fluorine dose such as ruptures of the stomach lining and nausea.Fluorine can also damage the parathyroid glands, leading to hyperparathyroidism, the uncontrolled secretion of parathyroid hormones. These hormones regulate calcium concentration in the body. An elevated parathyroid hormone concentration results in a depletion of calcium in bone structures and thus a higher calcium concentration in the blood. As a result, bone flexibility decreases making the bone more amenable to fractures.

text: Symptoms are mainly promoted in the bone structure. Due to a high fluorine concentration in the body, the bone is hardened and thus less elastic, resulting in an increased frequency of fractures. Other symptoms include thickening of the bone structure and accumulation of bone tissue, which both contribute to impaired joint mobility. Ligaments and cartilage can become ossified. Most patients suffering from skeletal fluorosis show side effects from the high fluorine dose such as ruptures of the stomach lining and nausea.Fluorine can also damage the

text: parathyroid gland

text: s, leading to hyperparathyroidism, the uncontrolled secretion of parathyroid hormones. These hormones regulate calcium concentration in the body. An elevated parathyroid hormone concentration results in a depletion of calcium in bone structures and thus a higher calcium concentration in the blood. As a result, bone flexibility decreases making the bone more amenable to fractures.

text: The endoskeleton is the internal support structure of an animal, composed of mineralized tissue and is typical of vertebrates. Endoskeletons vary in complexity from functioning purely for support (as in the case of sponges), to serving as an attachment site for muscles and a mechanism for transmitting muscular forces. A true endoskeleton is derived from mesodermal tissue. Such a skeleton is present in echinoderms and chordates.

text: The

text: endoskeleton

text: is the internal support structure of an

text: animal

text: , composed of

text: mineralized tissue

text: and is typical of

text: vertebrate

text: s. Endoskeletons vary in complexity from functioning purely for support (as in the case of

text: sponges

text: ), to serving as an attachment site for muscles and a mechanism for transmitting muscular forces. A true endoskeleton is derived from

text: mesodermal

text: tissue. Such a skeleton is present in

text: echinoderms

text: and

text: chordate

text: s.

text: Vertebrates can effect early seral stages. Herbivores may alter plant growth. Fossorial mammals could alter soil and plant community development. In a profound example, a seabird colony transfers considerable nitrogen into infertile soils, thereby altering plant growth. A keystone species may facilitate the introduction of pioneer species by creating new niches. For example, beavers may flood an area, allowing new species to immigrate.

text: Vertebrates can effect early seral stages.

text: Herbivore

text: s may alter plant growth. Fossorial mammals could alter soil and plant community development. In a profound example, a

text: seabird colony

text: transfers considerable nitrogen into infertile soils, thereby altering plant growth. A

text: keystone species

text: may facilitate the introduction of pioneer species by creating new

text: niches

text: . For example,

text: beaver

text: s may flood an area, allowing new species to immigrate.

text: Vertebrate paleontology in the United States originated in Philadelphia through the efforts of naturalists and scientists associated with the American Philosophical Society (APS) during the first decade of the 19th century and at The Academy of Natural Sciences thereafter. By the end of the 19th century, the holdings from the APS, including the Thomas Jefferson Fossil Collection, had been transferred to the Academy for safekeeping. Currently, the collection contains more than 22,000 specimens, including many types. Richard Harlan was an early member who introduced many American naturalists to the groundbreaking works of Georges Cuvier. Joseph Leidy, who described Hadrosaurus and alerted the scientific world to the paleontological treasures of the American West, is considered the "father" of American vertebrate paleontology. Edward Drinker Cope, who also worked extensively on other vertebrates, is best known for his rivalry with Othniel Charles Marsh during the infamous Bone Wars. Curator Edward B. Daeschler is currently studying the evolution of Devonian tetrapods. He is a co-discoverer of the transitional "fishapod" Tiktaalik roseae from the Canadian Arctic and the discoverer of two tetrapods, Hynerpeton and Densignathus from the Catskill Formation in Pennsylvania.

text: Vertebrate paleontology

text: in the United States originated in Philadelphia through the efforts of naturalists and scientists associated with the

text: American Philosophical Society

text: (APS) during the first decade of the 19th century and at The Academy of Natural Sciences thereafter. By the end of the 19th century, the holdings from the APS, including the Thomas Jefferson Fossil Collection, had been transferred to the Academy for safekeeping. Currently, the collection contains more than 22,000 specimens, including many types.

text: Richard Harlan

text: was an early member who introduced many American naturalists to the groundbreaking works of

text: Georges Cuvier

text: . Joseph Leidy, who described

text: Hadrosaurus

text: and alerted the scientific world to the paleontological treasures of the American West, is considered the "father" of American vertebrate paleontology.

text: Edward Drinker Cope

text: , who also worked extensively on other vertebrates, is best known for his rivalry with

text: Othniel Charles Marsh

text: during the infamous

text: Bone Wars

text: . Curator Edward B. Daeschler is currently studying the evolution of

text: Devonian

text: tetrapod

text: s. He is a co-discoverer of the transitional "fishapod"

text: Tiktaalik roseae

text: from the Canadian Arctic and the discoverer of two tetrapods,

text: Hynerpeton

text: and Densignathus from the

text: Catskill Formation

text: in Pennsylvania.

text: The presence of pharyngeal slits in hemichordates led to debates of whether this structure was homologous to the slits found in chordates or a result of convergent evolution.  With the placement of hemichordates and echinoderms as a sister group to chordates, a new hypothesis has emerged-suggesting that pharyngeal gill slits were present in the deuterostome ancestor .  Intriguingly, extant echinoderms lack pharyngeal structures, but fossil records reveal that ancestral forms of echinoderms had gill-like structures. Comparative developmental and genetic studies of these pharyngeal structures between hemichordates and urochordates have brought about important insights regarding the evolution of the deuterostome body plan.  Comparative molecular biology has revealed that the Pax1/9 genes (which encode for transcription factors) are expressed in similar patterns between hemichordates and urochordates; In vertebrates, Pax 1 and Pax 9 are expressed in the pharyngeal pouches and are important for thymus development.  applying excess retinoic acid (excess retincoic acid in vertebrates results in pharyngeal abnormalities) leads to the absence of gill slits in developing Amphioxus, suggesting that retinoic acid may act through the same mechanism in vertebrates and amphioxus.  These studies indicate that the pharyngeal slits found in hemichordates and chordates are indeed homologous in a molecular sense.

text: The presence of pharyngeal slits in hemichordates led to debates of whether this structure was homologous to the slits found in chordates or a result of

text: convergent evolution

text: .  With the placement of hemichordates and

text: echinoderms

text: as a sister group to chordates, a new hypothesis has emerged-suggesting that pharyngeal gill slits were present in the

text: deuterostome

text: ancestor .  Intriguingly,

text: extant

text: echinoderms lack pharyngeal structures, but fossil records reveal that ancestral forms of echinoderms had gill-like structures. Comparative developmental and genetic studies of these pharyngeal structures between hemichordates and

text: urochordates

text: have brought about important insights regarding the evolution of the deuterostome

text: body plan

text: .  Comparative molecular biology has revealed that the Pax1/9 genes (which encode for

text: transcription factors

text: ) are expressed in similar patterns between hemichordates and urochordates; In vertebrates, Pax 1 and Pax 9 are expressed in the pharyngeal pouches and are important for

text: thymus

text: development.  applying excess

text: retinoic acid

text: (excess retincoic acid in vertebrates results in pharyngeal abnormalities) leads to the absence of gill slits in developing

text: Amphioxus

text: , suggesting that retinoic acid may act through the same mechanism in vertebrates and amphioxus.  These studies indicate that the pharyngeal slits found in hemichordates and chordates are indeed homologous in a

text: molecular

text: sense.

text: Vertebral artery dissection is one of the two types of dissection of the arteries in the neck. The other type, carotid artery dissection, involves the carotid arteries. Vertebral artery dissection is further classified as being either traumatic (caused by mechanical trauma to the neck) or spontaneous, and it may also be classified by the part of the artery involved: extracranial (the part outside the skull) and intracranial (the part inside the skull).

text: Vertebral artery dissection is one of the two types of dissection of the arteries in the neck. The other type, carotid artery dissection, involves the

text: carotid arteries

text: . Vertebral artery dissection is further classified as being either traumatic (caused by mechanical trauma to the neck) or spontaneous, and it may also be classified by the part of the artery involved: extracranial (the part outside the skull) and intracranial (the part inside the skull).

text: Somites form in the early embryo and some of these develop into sclerotomes. The sclerotomes form the vertebrae as well as the rib cartilage and part of the occipital bone. From their initial location within the somite, the sclerotome cells migrate medially towards the notochord. These cells meet the sclerotome cells from the other side of the paraxial mesoderm. The lower half of one sclerotome fuses with the upper half of the adjacent one to form each vertebral body. From this vertebral body, sclerotome cells move dorsally and surround the developing spinal cord, forming the vertebral arch. Other cells move distally to the costal processes of thoracic vertebrae to form the ribs.

text: Somite

text: s form in the early

text: embryo

text: and some of these develop into sclerotomes. The sclerotomes form the vertebrae as well as the rib cartilage and part of the

text: occipital bone

text: . From their initial location within the somite, the sclerotome cells migrate medially towards the

text: notochord

text: . These cells meet the sclerotome cells from the other side of the

text: paraxial mesoderm

text: . The lower half of one sclerotome fuses with the upper half of the adjacent one to form each vertebral body. From this vertebral body, sclerotome cells move dorsally and surround the developing

text: spinal cord

text: , forming the

text: vertebral arch

text: . Other cells move distally to the costal processes of

text: thoracic vertebrae

text: to form the ribs.

text: In the lumbar region they are arranged in pairs, on either side of the vertebral column,

text: The first pelycosaurs had the usual reptilian cold-blooded metabolism by all indications, including a sprawling gait and a low slung body. Historically, it was assumed that the large "sails" in both edaphosaurids and some sphenacodontids (e.g. Dimetrodon) were utilised for temperature regulation, making them an early example of homeothermy. However, most modern researchers realise that the sails were probably display devices, useless for temperature control. Nonetheless, primitive endothermy might have existed within sphenacodontids.

text: The first pelycosaurs had the usual reptilian

text: cold-blooded

text: metabolism by all indications, including a sprawling gait and a low slung body. Historically, it was assumed that the large "sails" in both

text: edaphosaurids

text: and some

text: sphenacodontids

text: (e.g.

text: Dimetrodon

text: ) were utilised for temperature regulation, making them an early example of

text: homeothermy

text: . However, most modern researchers realise that the sails were probably display devices, useless for temperature control. Nonetheless, primitive endothermy might have existed within sphenacodontids.

text: Like all Plasmodium species P. georgesi has both vertebrate and insect hosts. The vertebrate hosts for this parasite are mammals.

text: Like all Plasmodium species P. georgesi has both

text: vertebrate

text: and

text: insect

text: mammal

text: s.

text: Leinkupal was a relatively small sauropod, with an estimated body length of nine metres. Several unique derived traits, or autapomorphies, could be established. The front tail vertebrae have extremely well-developed transverse processes, as long as the width of the vertebral body, expanded sideways and to below, and possessing robust reinforcing ridges on their top and bottom surfaces. The front tail vertebrae have very robust ridges running between the vertebral body and the front joint processes, the prezygapophyses. The front tail vertebrae have rear joint processes, postzygapophyses, with two paired pneumatic openings at their inner bases, opposite from the joint facets.

text: Leinkupal was a relatively small sauropod, with an estimated body length of nine metres. Several unique derived traits, or

text: autapomorphies

text: , could be established. The front tail vertebrae have extremely well-developed transverse processes, as long as the width of the vertebral body, expanded sideways and to below, and possessing robust reinforcing ridges on their top and bottom surfaces. The front tail vertebrae have very robust ridges running between the vertebral body and the front joint processes, the

text: prezygapophyses

text: . The front tail vertebrae have rear joint processes,

text: postzygapophyses

text: , with two paired pneumatic openings at their inner bases, opposite from the joint facets.

text: A bony fish clade known as the lobe-finned fishes is included with tetrapods, which are further divided into amphibians, reptiles, mammals, and birds. Extant vertebrates range in size from the frog species Paedophryne amauensis, at as little as , to the blue whale, at up to . Vertebrates make up less than five percent of all described animal species; the rest are invertebrates, which lack vertebral columns.

text: A bony

text: fish

text: clade known as the

text: lobe-finned fishes

text: is included with

text: tetrapods

text: , which are further divided into

text: amphibian

text: s,

text: reptile

text: s,

text: mammal

text: s, and

text: bird

text: s.

text: Extant

text: vertebrates range in size from the

text: frog

text: species

text: Paedophryne amauensis

text: , at as little as , to the

text: blue whale

text: , at up to . Vertebrates make up less than five percent of all described

text: animal species

text: ; the rest are

text: invertebrates

text: , which lack

text: vertebral column

text: s.

text: The hyomandibula of fish migrated upwards from its jaw supporting position, and was reduced in size to form the stapes. Situated between the tympanum and braincase in an air-filled cavity, the stapes was now capable of transmitting vibrations from the exterior of the head to the interior. Thus the stapes became an important element in an impedance matching system, coupling airborne sound waves to the receptor system of the inner ear. This system had evolved independently within several different amphibian lineages.

text: The

text: hyomandibula

text: of fish migrated upwards from its jaw supporting position, and was reduced in size to form the

text: stapes

text: . Situated between the tympanum and braincase in an air-filled cavity, the stapes was now capable of transmitting vibrations from the exterior of the head to the interior. Thus the stapes became an important element in an

text: impedance matching

text: system, coupling airborne sound waves to the receptor system of the inner ear. This system had evolved independently within several different amphibian

text: lineages

text: The hollow crest of Hypacrosaurus most likely had social functions, such as a visual signal allowing individuals to identify sex or species, and providing a resonating chamber for making noises. The crest and its associated nasal passages have also figured in the debate about dinosaur endothermy, specifically in discussions about nasal turbinates.

text: The hollow crest of Hypacrosaurus most likely had social functions, such as a visual signal allowing individuals to identify sex or species, and providing a resonating chamber for making noises. The crest and its associated nasal passages have also figured in the debate about

text: dinosaur endothermy

text: , specifically in discussions about

text: nasal turbinates

text: Zhou Mingzhen was born in Shanghai, China, and graduated from Chongqing University in Sichuan, in 1943. He received an MSc degree from the University of Miami, in 1948, and a Ph.D. degree from Lehigh University, in 1950. He became an associate professor at Shandong University, in 1952 and joined the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences in Beijing, where he remained until his death, in 1996. He was the Chinese leader of the "Sino-Soviet (Paleontological) Expedition" to northwestern China in 1959–1960.  In 1979, Zhou became an honorary member of the Society of Vertebrate Paleontology (SVP). He became an academician of the Chinese Academy of Sciences, in 1980 and in 1993 was awarded the SVP's Romer-Simpson medal for "sustained and outstanding scholarly excellence and service to the discipline of vertebrate paleontology".  He was an early and effective advocate of cladistic approaches to paleobiology in China, beginning in the early 1980s and promoted study abroad and academic training for young Chinese paleontologists, in the 1980s and 1990s.

text: Zhou Mingzhen was born in

text: Shanghai

text: China

text: , and graduated from

text: Chongqing University

text: in Sichuan, in 1943. He received an MSc degree from the

text: University of Miami

text: , in 1948, and a Ph.D. degree from

text: Lehigh University

text: , in 1950. He became an associate professor at

text: Shandong University

text: , in 1952 and joined the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences in

text: Beijing

text: , where he remained until his death, in 1996. He was the Chinese leader of the "Sino-Soviet (Paleontological) Expedition" to northwestern China in 1959–1960.  In 1979, Zhou became an honorary member of the

text: Society of Vertebrate Paleontology

text: (SVP). He became an academician of the Chinese Academy of Sciences, in 1980 and in 1993 was awarded the SVP's Romer-Simpson medal for "sustained and outstanding scholarly excellence and service to the discipline of vertebrate paleontology".  He was an early and effective advocate of cladistic approaches to paleobiology in China, beginning in the early 1980s and promoted study abroad and academic training for young Chinese paleontologists, in the 1980s and 1990s.

text: Human c-Raf is a member of a larger family of related protein kinases. Two further members - found in most vertebrates - belong to the same family: B-Raf and A-Raf. Apart from the different length of their non-conserved N- and C-terminal ends, they all share the same domain architecture, structure and regulation. In comparison to the relatively well-known c-Raf and B-Raf, there is very little known of the precise function of A-Raf, but it is also thought to be similar to the other two members of the family. All these genes are believed to be the product of full gene or genome duplications at the dawn of vertebrate evolution, from a single ancestral Raf gene. Most other animal organisms possess only a single Raf gene. It is called Phl or Draf in Drosophila and Lin-45 in C. elegans.

text: Human c-Raf is a member of a larger family of related protein kinases. Two further members - found in most vertebrates - belong to the same family:

text: B-Raf

text: and

text: A-Raf

text: . Apart from the different length of their non-conserved N- and C-terminal ends, they all share the same domain architecture, structure and regulation. In comparison to the relatively well-known c-Raf and B-Raf, there is very little known of the precise function of A-Raf, but it is also thought to be similar to the other two members of the family. All these genes are believed to be the product of full gene or genome duplications at the dawn of vertebrate evolution, from a single ancestral Raf gene. Most other animal organisms possess only a single Raf gene. It is called Phl or Draf in Drosophila and Lin-45 in C. elegans.

text: In 2012, facultative parthenogenesis was reported in wild vertebrates for the first time by US researchers amongst captured pregnant copperhead and cottonmouth female pit-vipers. The Komodo dragon, which normally reproduces sexually, has also been found able to reproduce asexually by parthenogenesis. A case has been documented of a Komodo dragon reproducing via sexual reproduction after a known parthenogenetic event, highlighting that these cases of parthenogenesis are reproductive accidents, rather than adaptive, facultative parthenogenesis.

text: Salvator merianae has recently been shown to be one of the few partially warm-blooded lizard, having a temperature up to 10 °C (18 °F) higher than the ambient temperature at night time. However, unlike true endotherms such as mammals and birds, these lizards only display temperature control during their reproductive season (September to December), and for that reason are said to possess seasonal reproductive endothermy. Because convergent evolution is one of the strongest lines of evidence for the adaptive significance of a trait, the discovery of reproductive endothermy in this lizard not only complements the long known reproductive endothermy observed in some species of pythons, but also supports the hypothesis that the initial selective benefit for endothermy in birds and mammals was reproductive

text: Salvator merianae has recently been shown to be one of the few partially warm-blooded lizard, having a temperature up to 10 °C (18 °F) higher than the ambient temperature at night time. However, unlike true endotherms such as mammals and birds, these lizards only display temperature control during their reproductive season (September to December), and for that reason are said to possess

text: seasonal reproductive endothermy

text: . Because convergent evolution is one of the strongest lines of evidence for the adaptive significance of a trait, the discovery of reproductive endothermy in this lizard not only complements the long known reproductive endothermy observed in some species of pythons, but also supports the hypothesis that the initial selective benefit for endothermy in birds and mammals was reproductive

text: B and T lymphocytes bearing immunoglobulins and T cell receptors, respectively, are found in all jawed fishes. Indeed, the adaptive immune system as a whole evolved in an ancestor of all jawed vertebrate.

text: B and T lymphocytes bearing

text: immunoglobulin

text: s and

text: T cell receptor

text: s, respectively, are found in all jawed fishes. Indeed, the

text: adaptive immune system

text: as a whole

text: evolved

text: in an ancestor of all jawed vertebrate.

text: Animals can be divided into two broad groups: vertebrates (animals with a backbone) and invertebrates (animals without a backbone). Half of all described vertebrate species are fishes and three-quarters of all described invertebrate species are insects. The following table lists the number of described extant species for each major animal subgroup as estimated for the IUCN Red List of Threatened Species, 2014.3.

text: Animals can be divided into two broad groups:

text: vertebrate

text: s (animals with a

text: backbone

text: ) and

text: invertebrate

text: s (animals without a backbone). Half of all described vertebrate species are fishes and three-quarters of all described invertebrate species are insects. The following table lists the number of described

text: extant

text: species for each major animal subgroup as estimated for the

text: IUCN Red List of Threatened Species

text: , 2014.3.

text: Known members of the family include DLX1 to DLX6. They form two-gene clusters (bigene clusters) with each other. There are DLX1-DLX2, DLX3-DLX4, DLX5-DLX6 clusters in vertebrates. Each of those are linked to a specific Hox gene cluster. In higher fishes, like Zebrafish, there are a couple of additional DLX genes, DLX5 and DLX8. In zebrafish the orthologous genes to vertebrate DLX5-DLX6 are DLX4 and DLX6, which form a bigene cluster in zebrafish. These additional genes are not linked with each other, or any other DLX gene.

text: Known members of the family include

text: to

text: . They form two-gene

text: cluster

text: s (bigene clusters) with each other. There are DLX1-

text: -DLX6 clusters in vertebrates. Each of those are linked to a specific

text: Hox gene

text: cluster. In higher fishes, like

text: Zebrafish

text: , there are a couple of additional DLX genes, DLX5 and DLX8. In zebrafish the orthologous genes to vertebrate DLX5-DLX6 are DLX4 and DLX6, which form a bigene cluster in zebrafish. These additional genes are not linked with each other, or any other DLX gene.

text: The cladogram shows the relationship of the Holostei to other bony fish, the great majority of which are Teleosts, and to the terrestrial vertebrates (tetrapods) that evolved from a related group of fish. Approximate dates are from Near et al., 2012.

text: The

text: cladogram

text: shows the relationship of the Holostei to other bony fish, the great majority of which are

text: Teleost

text: s, and to the terrestrial vertebrates (tetrapods) that evolved from a related group of fish. Approximate dates are from Near et al., 2012.

text: In the railway industry, there are risk factors involved with the prolonged usage of maintenance of way vehicles by vehicle operators during day-to-day track maintenance and construction. A common risk factor is prolonged exposure to excessive whole body vibration and shock exposure to the vertical and horizontal axis' of the lumbar spine and vertebral endplate which can lead to spinal injury and or long term damage to the vertebral bone structure. The American Conference of Governmental Industrial Hygienists has in the past proposed threshold limit values for whole body vibration with certain guidelines also being based on ISO-2631 standards, but no official exposure threshold limits for maintenance of way vehicles have seen widespread publication or enforcement. The ACGIH-TLV limits worker whole body vibration exposure to no more than 8 hours in duration. In the European Union a new risk assessment model (VibRisk model) for structural failure of the lumbar spine in the lower back was proposed as a result of vibration risk research. The VibRisk model provides more specific risk assessments of vertebral endplate failure on individual lumbar levels taking into account driver posture. When compared the risk assessment proposed using the VibRisk Model posed a higher risk of vertebral endplate failure at different lumbar levels than ISO-2631 Part 5 standards suggested. The main contributing factor that VibRisk incorporates that the ISO-2631 Part 5 standards are lacking is the recognition of operator posture as an additional stress factor when exposed to vibration and multiple shocks.

text: In the railway industry, there are risk factors involved with the prolonged usage of maintenance of way vehicles by vehicle operators during day-to-day track maintenance and construction. A common risk factor is prolonged exposure to excessive

text: whole body vibration

text: and shock exposure to the vertical and horizontal axis' of the

text: lumbar

text: spine and

text: vertebral

text: endplate which can lead to spinal injury and or long term damage to the vertebral bone

text: structure

text: . The American Conference of Governmental Industrial Hygienists has in the past proposed threshold limit values for whole body vibration with certain guidelines also being based on ISO-2631 standards, but no official exposure threshold limits for maintenance of way vehicles have seen widespread publication or enforcement. The ACGIH-TLV limits worker whole body vibration exposure to no more than 8 hours in duration. In the European Union a new risk assessment model (VibRisk model) for structural failure of the lumbar spine in the lower back was proposed as a result of vibration risk research. The VibRisk model provides more specific risk assessments of vertebral endplate failure on individual lumbar levels taking into account driver posture. When compared the risk assessment proposed using the VibRisk Model posed a higher risk of vertebral endplate failure at different lumbar levels than ISO-2631 Part 5 standards suggested. The main contributing factor that VibRisk incorporates that the ISO-2631 Part 5 standards are lacking is the recognition of operator posture as an additional stress factor when exposed to vibration and multiple shocks.

text: Stichopus chloronotus can reproduce asexually by undergoing transverse fission, forming two new individuals which each regenerate the missing parts. It can also reproduce sexually.

text: Stichopus chloronotus can reproduce asexually by undergoing

text: transverse fission

text: , forming two new individuals which each regenerate the missing parts. It can also reproduce sexually.

text: This shark is known from the fossil teeth and fossilized vertebral centra. Like other elasmobranchs, the skeleton of Otodus was composed of cartilage and not bone, resulting in relatively few preserved skeletal structures appearing within the fossil record. The teeth of this shark are large with triangular crown, smooth cutting edges, and visible cusps on the roots. Some Otodus teeth also show signs of evolving serrations.

text: This shark is known from the

text: fossil

text: teeth

text: and fossilized

text: vertebral centra

text: . Like other

text: elasmobranch

text: s, the

text: skeleton

text: of Otodus was composed of

text: cartilage

text: and not

text: bone

text: , resulting in relatively few preserved skeletal structures appearing within the fossil record. The teeth of this shark are large with triangular crown, smooth cutting edges, and visible cusps on the roots. Some Otodus teeth also show signs of evolving serrations.

text: Although it is known that Antp-class homeobox genes play some sort of role in transcriptional processes, not all of their actions and functions have been discovered.  Recent studies observed Antp and the Hox ortholog HoxC6 in Xenopus in order to further distinguish the evolution of these orthologues. HoxC6 was found to play an important role in gastrulation in the vertebrate Xenopus. However, gastrulation was also a target in the Drosophila Antp gene. The anterior-posterior pattern mechanism is highly conserved in these genes, as its function in Xenopus is clear, but it is unclear why it would be a target in Drosophila. The similarities continuously observed between Hox genes in vertebrates and Drosophila suggests a complex evolutionary history of the Antp Hox gene cluster, as well as reaffirms the importance of the conservation of this gene cluster in the evolution of body morphology.

text: Although it is known that Antp-class homeobox genes play some sort of role in

text: transcription

text: al processes, not all of their actions and functions have been discovered.  Recent studies observed Antp and the Hox ortholog HoxC6 in Xenopus in order to further distinguish the evolution of these orthologues. HoxC6 was found to play an important role in

text: gastrulation

text: in the vertebrate Xenopus. However, gastrulation was also a target in the Drosophila Antp gene. The anterior-posterior pattern mechanism is highly conserved in these genes, as its function in Xenopus is clear, but it is unclear why it would be a target in Drosophila. The similarities continuously observed between Hox genes in vertebrates and Drosophila suggests a complex evolutionary history of the Antp Hox gene cluster, as well as reaffirms the importance of the conservation of this gene cluster in the evolution of body morphology.

text: Velpeau, who read an article, demonstrated that he was the first who used the ligature of the vertebral artery and indicated how to find it.

text: Velpeau, who read an article, demonstrated that he was the first who used the ligature of the

text: vertebral artery

text: and indicated how to find it.

text: In vertebrates, the pharyngeal arches are derived from all three germ layers. Neural crest cells enter these arches where they contribute to craniofacial features such as bone and cartilage. However, the existence of pharyngeal structures before neural crest cells evolved is indicated by the existence of neural crest-independent mechanisms of pharyngeal arch development.<ref name= archevo>{{cite journal |vauthors=Graham A, Smith A |title= Patterning the pharyngeal arches|journal= BioEssays|volume=23|issue= 1|pages=54–61|year= 2001|pmid=11135309 |doi=10.1002/1521-1878(200101)23:1

text: In vertebrates, the pharyngeal arches are derived from all three

text: germ layers

text: Neural crest cells

text: enter these arches where they contribute to craniofacial features such as bone and cartilage. However, the existence of pharyngeal structures before neural crest cells evolved is indicated by the existence of neural crest-independent mechanisms of pharyngeal arch development.<ref name= archevo>{{cite journal |vauthors=Graham A, Smith A |title= Patterning the pharyngeal arches|journal= BioEssays|volume=23|issue= 1|pages=54–61|year= 2001|pmid=11135309 |doi=10.1002/1521-1878(200101)23:1

text: If hyaline cartilage is torn all the way down to the bone, the blood supply from inside the bone is sometimes enough to start some healing inside the lesion. In cases like this, the body will form a scar in the area using a special type of cartilage called fibrocartilage. Fibrocartilage is a tough, dense, and fibrous material that helps fill in the torn part of the cartilage; however, it is not an ideal replacement for the smooth, glassy articular cartilage that normally covers the surface of joints.

text: If

text: hyaline cartilage

text: is torn all the way down to the bone, the blood supply from inside the bone is sometimes enough to start some healing inside the lesion. In cases like this, the body will form a scar in the area using a special type of cartilage called fibrocartilage. Fibrocartilage is a tough, dense, and fibrous material that helps fill in the torn part of the cartilage; however, it is not an ideal replacement for the smooth, glassy articular cartilage that normally covers the surface of joints.

text: The side, or subaural knot, has been shown to produce other, more complex injuries, with one thoroughly studied case producing only ligamentous injuries to the cervical spine and bilateral vertebral artery disruptions, but no major vertebral fractures or crush injuries to the spinal cord. Death from a "hangman's fracture" occurs mainly when the applied force is severe enough to also cause a severe subluxation of the C2 and C3 vertebra that crushes the spinal cord and/or disrupts the vertebral arteries. Hangman's fractures from other hyperextension injuries (the most common being unrestrained motor vehicle accidents and falls or diving injuries where the face or chin suddenly strike an immovable object) are frequently survivable if the applied force does not cause a severe subluxation of C2 on C3.

text: The side, or subaural knot, has been shown to produce other, more complex injuries, with one thoroughly studied case producing only ligamentous injuries to the cervical spine and bilateral vertebral artery disruptions, but no major vertebral fractures or crush injuries to the spinal cord. Death from a "hangman's fracture" occurs mainly when the applied force is severe enough to also cause a severe

text: subluxation

text: of the C2 and C3 vertebra that crushes the spinal cord and/or disrupts the vertebral arteries. Hangman's fractures from other hyperextension injuries (the most common being unrestrained motor vehicle accidents and falls or diving injuries where the face or chin suddenly strike an immovable object) are frequently survivable if the applied force does not cause a severe subluxation of C2 on C3.

text: Fish hold records for the relative brain weights of vertebrates. Most vertebrate species have similar brain-to-body mass ratios. The deep sea bathypelagic bony-eared assfish, has the  smallest ratio of all known vertebrates. At the other extreme, the electrogenic elephantnose fish, an African freshwater fish, has one of the largest brain-to-body weight ratios of all known vertebrates (slightly higher than humans) and the highest brain-to-body oxygen consumption ratio of all known vertebrates (three times that for humans).

text: Fish hold records for the

text: relative brain weights

text: of vertebrates. Most vertebrate species have similar brain-to-body mass ratios. The deep sea bathypelagic

text: bony-eared assfish

text: , has the  smallest ratio of all known vertebrates. At the other extreme, the electrogenic

text: elephantnose fish

text: , an African freshwater fish, has one of the largest brain-to-body weight ratios of all known vertebrates (slightly higher than humans) and the highest brain-to-body oxygen consumption ratio of all known vertebrates (three times that for humans).

text: On its course the artery takes several small branches (i.e. anterior segmental medullary arteries), which enter the vertebral canal through the intervertebral foramina. These branches are derived from the vertebral artery, the ascending cervical artery, a branch of the inferior thyroid artery in the neck, the intercostal arteries in the thorax, and from the lumbar artery, iliolumbar artery and lateral sacral arteries in the abdomen and pelvis.

text: On its course the artery takes several small branches (i.e.

text: anterior segmental medullary arteries

text: ), which enter the

text: vertebral canal

text: through the

text: intervertebral foramina

text: . These branches are derived from the

text: vertebral artery

text: , the

text: ascending cervical artery

text: , a branch of the

text: inferior thyroid artery

text: in the neck, the

text: intercostal arteries

text: in the

text: thorax

text: , and from the

text: lumbar artery

text: iliolumbar artery

text: and

text: lateral sacral arteries

text: in the

text: abdomen

text: and

text: pelvis

text: The overall rate of an animal's metabolism increases by a factor of about two for every  rise in temperature, limited by the need to avoid hyperthermia. Endothermy does not provide greater speed in movement than ectothermy (cold-bloodedness)—ectothermic animals can move as fast as warm-blooded animals of the same size and build when the ectotherm is near or at its optimum temperature, but often cannot maintain high metabolic activity for as long as endotherms.  Endothermic/homeothermic animals can be optimally active at more times during the diurnal cycle in places of sharp temperature variations between day and night and during more of the year in places of great seasonal differences of temperature.  This is accompanied by the need to expend more energy to maintain the constant internal temperature and a greater food requirement.  Endothermy may be important during reproduction, for example, in expanding the thermal range over which a species can reproduce, as embryos are generally intolerant of thermal fluctuations that are easily tolerated by adults. Endothermy may also provide a protection against fungal infection. While tens of thousands of fungal species infect insects, only a few hundred target mammals, and often only those with a compromised immune system. A recent studysuggests fungi are fundamentally ill-equipped to thrive at mammalian temperatures. The high temperatures afforded by endothermy might have provided an evolutionary advantage.

text: The overall rate of an animal's

text: metabolism

text: increases by a factor of about two for every  rise in

text: temperature

text: , limited by the need to avoid

text: hyperthermia

text: . Endothermy does not provide greater speed in movement than ectothermy (cold-bloodedness)—ectothermic animals can move as fast as warm-blooded animals of the same size and build when the ectotherm is near or at its optimum temperature, but often cannot maintain high metabolic activity for as long as endotherms.  Endothermic/homeothermic animals can be optimally active at more times during the diurnal cycle in places of sharp temperature variations between day and night and during more of the year in places of great

text: season

text: al differences of temperature.  This is accompanied by the need to expend more energy to maintain the constant internal temperature and a greater food requirement.  Endothermy may be important during reproduction, for example, in expanding the thermal range over which a species can reproduce, as embryos are generally intolerant of thermal fluctuations that are easily tolerated by adults. Endothermy may also provide a protection against

text: fungal

text: infection. While tens of thousands of fungal species infect insects, only a few hundred target mammals, and often only those with a compromised

text: immune system

text: . A recent studysuggests fungi are fundamentally ill-equipped to thrive at mammalian temperatures. The high temperatures afforded by endothermy might have provided an evolutionary advantage.

text: Sauropod necks were probably highly muscled to suit their feeding level. Brachiosaurus brancai (now Giraffititan) was probably a high browser, so it would have been more muscled along the neck than other sauropods like Diplodocus and Dicraeosaurus who were low browsers. The tail and limb length of B. brancai would also need to greater, to balance out the inclined neck. However, the question of whether sauropods were endothermic of ectothermic plays a major part in how sauropods were muscled, as endotherms have particularly more intestines and stomach than ectotherms. The amount of gut needed could determine how much food was eaten by sauropods, and therefore at what elevation there heads were held.

text: Sauropod necks were probably highly muscled to suit their feeding level.

text: Brachiosaurus brancai

text: (now

text: Giraffititan

text: ) was probably a high browser, so it would have been more muscled along the neck than other sauropods like Diplodocus and Dicraeosaurus who were low browsers. The tail and limb length of B. brancai would also need to greater, to balance out the inclined neck. However, the question of whether sauropods were

text: endothermic

text: of

text: ectothermic

text: plays a major part in how sauropods were muscled, as endotherms have particularly more intestines and stomach than ectotherms. The amount of gut needed could determine how much food was eaten by sauropods, and therefore at what elevation there heads were held.

text: Like all Plasmodium species P. megalotrypa has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. megalotrypa has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: In long bones, bone tissue first appears in the diaphysis (middle of shaft). Chondrocytes multiply and form trebeculae. Cartilage is progressively eroded and replaced by hardened bone, extending towards the epiphysis. A perichondrium layer surrounding the cartilage forms the periosteum, which generates osteogenic cells that then go on to make a collar that encircles the outside of the bone and remodels the medullary cavity on the inside.

text: In long bones, bone tissue first appears in the

text: diaphysis

text: (middle of shaft).

text: Chondrocyte

text: s multiply and form trebeculae. Cartilage is progressively eroded and replaced by hardened bone, extending towards the

text: epiphysis

text: . A

text: perichondrium

text: layer surrounding the cartilage forms the

text: periosteum

text: , which generates osteogenic cells that then go on to make a collar that encircles the outside of the bone and remodels the medullary cavity on the inside.

text: Because endothermy allows refined neuromuscular control, and because brain matter requires large amounts of energy to sustain, some speculate that increased brain size indicates increased activity and, thus, endothermy. The encephalization quotient (EQ) of dinosaurs, a measure of brain size calculated using brain endocasts, varies on a spectrum from bird-like to reptile-like. Using EQ alone, coelosaurs appear to have been as active as living mammals, while theropods and ornithopods fall somewhere between mammals and reptiles, and other dinosaurs resemble reptiles.

text: Classes of vertebrates listed in chronological order from oldest to most recent include heterostracans, osteostracans, coelolepid agnathans, acanthodians, osteichthyan fishes, chondrichthyan fishes, amphibians, reptiles, mammals, and birds. All vertebrates are studied under standard evolutionary generalizations of behavior and life process, although there is controversy over whether population can be accurately estimated from limited fossil resources.

text: Src family kinase is a family of non-receptor tyrosine kinases that includes nine members: Src, Yes, Fyn, and Fgr, forming the SrcA subfamily, Lck, Hck,  Blk, and Lyn in the SrcB subfamily,  and Frk in its own subfamily. Frk has homologs in invertebrates such as flies and worms, and Src homologs exist in organisms as diverse as unicellular choanoflagellates, but the SrcA and SrcB subfamilies are specific to vertebrates.

text: Src family kinase is a family of

text: non-receptor tyrosine kinase

text: s that includes nine members:

entity_name: Proto-oncogene tyrosine-protein kinase Src

text: Src

text: Yes

text: Fyn

text: , and

text: Fgr

text: , forming the SrcA subfamily,

text: Lck

text: Hck

text: ,  Blk, and

text: Lyn

text: in the SrcB subfamily,  and

text: Frk

text: in its own subfamily. Frk has homologs in

text: invertebrate

text: s such as flies and worms, and Src homologs exist in organisms as diverse as unicellular

text: choanoflagellate

text: s, but the SrcA and SrcB subfamilies are specific to vertebrates.

text: These parts were located with the aid of his original method of channelled deep preparation from the depth of the stone plate. The important place in the science remained for his other papers on fossil vertebrates. Petronijević's contributions to the philosophy of natural sciences are notable. Among them there are the explanation of the Dollo's law of irreversibility, the introduction of his own law of non-correlative evolution and detailed explanation of various segments of universal evolution.

text: These parts were located with the aid of his original method of channelled deep preparation from the depth of the stone plate. The important place in the science remained for his other papers on fossil vertebrates. Petronijević's contributions to the philosophy of

text: natural sciences

text: are notable. Among them there are the explanation of the

text: Dollo's law of irreversibility

text: , the introduction of his own law of non-correlative evolution and detailed explanation of various segments of universal evolution.

text: A famous example is the trait of breathing via gills in bony fish and cartilaginous fish. Bony fish are more closely related to terrestrial vertebrates, which evolved out of a clade of bony fishes that breathe through their skin or lungs, than they are to the sharks, rays, and the other cartilaginous fish. Their kind of gill respiration is shared by the "fishes" because it was present in their common ancestor and lost in the other living vertebrates. But based on this shared trait, we cannot infer that bony fish are more closely related to sharks and rays than they are to terrestrial vertebrates.

text: A famous example is the trait of breathing via

text: gills

text: in

text: bony fish

text: and

text: cartilaginous fish

text: . Bony fish are more closely related to

text: terrestrial vertebrates

text: , which evolved out of a clade of bony fishes that breathe through their skin or lungs, than they are to the

text: shark

text: s,

text: rays

text: , and the other cartilaginous fish. Their kind of gill respiration is shared by the "fishes" because it was present in their common ancestor and lost in the other living

text: vertebrate

text: s. But based on this shared trait, we cannot infer that bony fish are more closely related to sharks and rays than they are to terrestrial vertebrates.

text: Dr Carroll is the author or co-author of a large number of scientific papers on fossil vertebrates, as well as a number of important monographs, text-books and more general books. His areas of research include the origins of terrestrial vertebrates, the origin and early evolutionary radiation of amniotes, the origin and interrelationships of the Lissamphibian groups, the anatomy and relationship of Paleozoic and Mesozoic amphibians and reptiles, large scale patterns and processes of vertebrate evolution, and the use of Mesozoic marine reptiles as a model for investigating factors controlling the patterns and rates of evolution.

text: Dr Carroll is the author or co-author of a large number of scientific papers on fossil vertebrates, as well as a number of important monographs, text-books and more general books. His areas of research include the origins of terrestrial vertebrates, the origin and early evolutionary radiation of amniotes, the origin and interrelationships of the

text: Lissamphibia

text: n groups, the anatomy and relationship of Paleozoic and Mesozoic amphibians and reptiles, large scale patterns and processes of vertebrate evolution, and the use of Mesozoic marine reptiles as a model for investigating factors controlling the patterns and rates of evolution.

text: This episode goes through how the vertebrates evolved and came onto land. It details the origins of the vertebrates, which lie in the primitive fish that once swam in ancient seas. Remarkable advances allowed them to make the radical move onto land, and then take to the skies with the advent of flight. Brand new discoveries of fossils - ancient and living - combined with stunning CGI enable David to chart their unexpected journey out of the water to populate all corners of the globe.

text: Since approximately 450 years ago, two pathways have been acknowledged for transmitting sound to the inner ear; one is air conduction and the other is bone conduction. In 2004, Hiroshi Hosoi, a professor at Nara Medical University, discovered the phenomenon of cartilage vibration in the inner ear. By attaching a vibrator to aural cartilage, sound was found be transmitted into the inner ear well. He proposed the novel concept that cartilage has a unique characteristic capable of transmitting sound. Because sound transmission via pathways that use air or bone are respectively called air conduction and bone conduction, the new pathway is referred to as cartilage conduction. This unique pathway has attracted the attention of several researchers and companies such that some hearing aid prototypes using cartilage conduction have been tested for use in smartphone and earphone.

text: Since approximately 450 years ago, two pathways have been acknowledged for transmitting sound to the inner ear; one is air conduction and the other is bone conduction. In 2004, Hiroshi Hosoi, a professor at Nara Medical University, discovered the phenomenon of cartilage vibration in the inner ear. By attaching a

text: vibrator

text: to aural cartilage, sound was found be transmitted into the inner ear well. He proposed the novel concept that cartilage has a unique characteristic capable of transmitting sound. Because sound transmission via pathways that use air or bone are respectively called air conduction and

text: bone conduction

text: , the new pathway is referred to as cartilage conduction. This unique pathway has attracted the attention of several researchers and companies such that some

text: hearing aid

text: prototypes using cartilage conduction have been tested for use in

text: smartphone

text: and

text: earphone

text: Fish are the ancestors of all mammals, reptiles, birds and amphibians. In particular, terrestrial tetrapods (four-legged animals) evolved from fish and made their first forays onto land 400 million years ago. They used paired pectoral and pelvic fins for locomotion. The pectoral fins developed into forelegs (arms in the case of humans) and the pelvic fins developed into hind legs. Much of the genetic machinery that builds a walking limb in a tetrapod is already present in the swimming fin of a fish.

text: Fish are the ancestors of all mammals, reptiles, birds and amphibians. In particular, terrestrial

text: tetrapod

text: s (four-legged animals) evolved from fish and made their first forays onto land 400 million years ago. They used paired pectoral and pelvic fins for locomotion. The pectoral fins developed into forelegs (arms in the case of humans) and the pelvic fins developed into hind legs. Much of the genetic machinery that builds a walking limb in a tetrapod is already present in the swimming fin of a fish.

text: Two ideas about the homology of arms, hands and digits have existed in the past 130 years. First that digits are unique to tetrapods  and second that antecedents were present in the fins of early sarcopterygian fish. Until recently it was believed that "genetic and fossil data support the hypothesis that digits are evolutionary novelties". However new research that created a three-dimensional reconstruction of Panderichthys, a coastal fish from the Devonian period 385 million years ago, shows that these animals already had many of the homologous bones present in the forelimbs of limbed vertebrates. For example, they had radial bones similar to rudimentary fingers but positioned in the arm-like base of their fins.  Thus there was in the evolution of tetrapods a shift such that the outermost part of the fins were lost and eventually replaced by early digits. This change is consistent with additional evidence from the study of actinopterygians, sharks and lungfish that the digits of tetrapods arose from pre-existing distal radials present in more primitive fish. Controversy still exists since Tiktaalik, a vertebrate often considered the missing link between fishes and land-living animals, had stubby leg-like limbs that lacked the finger-like radial bones found in the Panderichthys. The researchers of the paper commented that it "is difficult to say whether this character distribution implies that Tiktaalik is autapomorphic, that Panderichthys and tetrapods are convergent, or that Panderichthys is closer to tetrapods than Tiktaalik. At any rate, it demonstrates that the fish–tetrapod transition was accompanied by significant character incongruence in functionally important structures.".

text: Two ideas about the

text: homology

text: of arms, hands and digits have existed in the past 130 years. First that digits are unique to tetrapods  and second that antecedents were present in the fins of early

text: sarcopterygian

text: fish. Until recently it was believed that "genetic and fossil data support the hypothesis that digits are evolutionary novelties". However new research that created a three-dimensional reconstruction of

text: Panderichthys

text: , a coastal fish from the

text: Devonian

text: period 385 million years ago, shows that these animals already had many of the homologous bones present in the forelimbs of limbed vertebrates. For example, they had

text: radial

text: bones similar to rudimentary fingers but positioned in the arm-like base of their fins.  Thus there was in the evolution of

text: tetrapod

text: s a shift such that the outermost part of the fins were lost and eventually replaced by early digits. This change is consistent with additional evidence from the study of

text: actinopterygian

text: s,

text: shark

text: s and

text: lungfish

text: that the digits of tetrapods arose from pre-existing distal radials present in more primitive fish. Controversy still exists since

text: Tiktaalik

text: , a vertebrate often considered the

text: missing link

text: between fishes and land-living animals, had stubby leg-like limbs that lacked the finger-like radial bones found in the Panderichthys. The researchers of the paper commented that it "is difficult to say whether this character distribution implies that Tiktaalik is

text: autapomorph

text: ic, that Panderichthys and tetrapods are convergent, or that Panderichthys is closer to tetrapods than Tiktaalik. At any rate, it demonstrates that the fish–tetrapod transition was accompanied by significant character incongruence in functionally important structures.".

text: The following steps are followed in the conversion of cartilage to bone:

text: The movement of shaking or rotating the head left and right happens almost entirely at the joint between the atlas and the axis, the atlanto-axial joint. A small amount of rotation of the vertebral column itself contributes to the movement. This movement between the atlas and axis is often referred to as the "no joint", owing to its nature of being able to rotate the head in a side-to-side fashion.

text: The movement of shaking or rotating the head left and right happens almost entirely at the joint between the atlas and the axis, the

text: atlanto-axial joint

text: . A small amount of rotation of the vertebral column itself contributes to the movement. This movement between the atlas and axis is often referred to as the "no joint", owing to its nature of being able to rotate the head in a side-to-side fashion.

text: Using fossil evidence, studies have shown that vertebrate biodiversity has grown exponentially through Earth's history and that biodiversity is entwined with the diversity of Earth's habitats.

text: Vertebrate Paleontology and Evolution appeared in print in 1988, just before the cladistic taxonomy became popular in vertebrate paleontology. The books thus uses the classical systematic scheme, including a number of paraphyletic taxa that are not recognised under phylogenetic nomenclature.

text: Vertebrate Paleontology and Evolution appeared in print in 1988, just before the

text: cladistic

text: taxonomy became popular in vertebrate paleontology. The books thus uses the classical systematic scheme, including a number of

text: paraphyletic

text: taxa that are not recognised under

text: phylogenetic nomenclature

text: Vultures possess a very acidic digestive system and their gut is dominated by two species of anaerobic bacteria that help them withstand toxins they ingest when feeding on decaying prey. In a 2014 study of 50 (turkey and black) vultures, researchers analyzed the microbial community or microbiome of the facial skin and the large intestine. The facial bacterial flora and the gut flora overlapped somewhat, but in general, the facial flora was much more diverse than the gut flora, which is in contrast to other vertebrates, where the gut flora is more diverse. Two anaerobic faecal bacteria groups that are pathogenic in other vertebrates stood out: Clostridia and Fusobacteria. They were especially common in the gut with Clostridia DNA sequence counts between 26% and 85% relative to total sequence counts, and Fusobacteria between 0.2% and 54% in black vultures and  2% to 69% of all counts in turkey vultures. Unexpectedly, both anaerobic bacteria were also found on the air exposed facial skin samples, Clostridia at 7%–40% and Fusobacteria up to 23%. It is assumed that vultures acquire them when they insert their heads into the body cavities of rotten meat. The regularly ingested Clostridia and Fusobacteria outcompete other bacterial groups in the gut and become predominant. Genes that encode tissue-degrading enzymes and toxins that are associated with Clostridium perfringens have been found in the vulture gut metagenome. This supports the hypothesis that vultures do benefit from the bacterial breakdown of carrion, while at the same time tolerating the bacterial toxins.

text: Vultures possess a very acidic digestive system and their gut is dominated by two species of anaerobic bacteria that help them withstand

text: toxin

text: s they ingest when feeding on decaying prey. In a 2014 study of 50 (turkey and black) vultures, researchers analyzed the microbial community or

text: microbiome

text: of the facial skin and the large intestine. The facial bacterial flora and the gut flora overlapped somewhat, but in general, the facial flora was much more

text: diverse

text: than the gut flora, which is in contrast to other vertebrates, where the gut flora is more diverse. Two

text: anaerobic

text: faecal bacteria groups that are pathogenic in other vertebrates stood out:

text: Clostridia

text: and

text: Fusobacteria

text: . They were especially common in the gut with Clostridia

text: DNA sequence

text: counts between 26% and 85% relative to total sequence counts, and Fusobacteria between 0.2% and 54% in black vultures and  2% to 69% of all counts in turkey vultures. Unexpectedly, both anaerobic bacteria were also found on the air exposed facial skin samples, Clostridia at 7%–40% and Fusobacteria up to 23%. It is assumed that vultures acquire them when they insert their heads into the body cavities of rotten meat. The regularly ingested Clostridia and Fusobacteria outcompete other bacterial groups in the gut and become predominant. Genes that encode tissue-degrading enzymes and toxins that are associated with

text: Clostridium perfringens

text: have been found in the vulture gut

text: metagenome

text: . This supports the hypothesis that vultures do benefit from the bacterial breakdown of carrion, while at the same time tolerating the bacterial toxins.

text: The endoskeleton is actuated by a powerful network of hydraulic servomechanisms, making Terminators superhumanly strong. For instance, in the third movie, Schwarzenegger's character was able to handle firing a Browning .30 machine gun from the hip with one hand, while holding a coffin containing an alive John Connor and a heavy cache of weapons, showing no signs of the extra weight being any real concern.

text: The

text: endoskeleton

text: is actuated by a powerful network of

text: hydraulic

text: servomechanism

text: s, making Terminators

text: superhumanly strong

text: . For instance, in the third movie, Schwarzenegger's character was able to handle firing a

text: Browning .30

text: machine gun from the hip with one hand, while holding a coffin containing an alive John Connor and a heavy cache of weapons, showing no signs of the extra weight being any real concern.

text: The role of Osedax in the degradation of marine vertebrate remains is controversial. Some scientists think that Osedax is a specialist on whalebones while others think that it is more of a generalist. This controversy is due to a biogeographic paradox: despite the rarity and ephemeral nature of whale falls, Osedax has a broad biogeographic range and is surprisingly diverse. One hypothesis advanced to explain this paradox is that Osedax are able to colonize a variety of vertebrate remains besides whalebones. This hypothesis is supported by an experiment involving cow bones suspended above the sea floor. A variety of Osedax species successfully colonized these bones. Osedax have also been observed colonizing terrestrial mammal bones mixed in with galley waste from a surface vessel. Other scientists have countered this hypothesis by pointing out how the cow bone experiment does not match any natural habitat and also the low probability of terrestrial mammal bones arriving at the ocean floor in significant quantities. They also point out other cases of food falls in which the remains disappeared too swiftly for Osedax colonization and the lack of any observed colonization in similar cases. The true role of Osedax in the degradation of marine vertebrate remains is important to marine vertebrate taphonomy. Burrows closely similar to those made by Osedax species have been found in the bones of ancient marine birds and plesiosaurs, suggesting that the genus may once have had a wider range of foods.

text: The role of Osedax in the degradation of marine vertebrate remains is controversial. Some scientists think that Osedax is a specialist on whalebones while others think that it is more of a generalist. This controversy is due to a

text: biogeographic

text: paradox: despite the rarity and ephemeral nature of

text: whale fall

text: s, Osedax has a broad biogeographic range and is surprisingly diverse. One hypothesis advanced to explain this paradox is that Osedax are able to colonize a variety of vertebrate remains besides whalebones. This hypothesis is supported by an experiment involving cow bones suspended above the sea floor. A variety of Osedax species successfully colonized these bones. Osedax have also been observed colonizing terrestrial mammal bones mixed in with galley waste from a surface vessel. Other scientists have countered this hypothesis by pointing out how the cow bone experiment does not match any natural habitat and also the low probability of terrestrial mammal bones arriving at the ocean floor in significant quantities. They also point out other cases of food falls in which the remains disappeared too swiftly for Osedax colonization and the lack of any observed colonization in similar cases. The true role of Osedax in the degradation of marine vertebrate remains is important to marine vertebrate

text: taphonomy

text: . Burrows closely similar to those made by Osedax species have been found in the bones of

text: ancient marine birds

text: and

text: plesiosaur

text: s, suggesting that the genus may once have had a wider range of foods.

text: The vertebrae of lobe-finned fishes consist of three discrete bony elements. The vertebral arch surrounds the spinal cord, and is of broadly similar form to that found in most other vertebrates. Just beneath the arch lies a small plate-like pleurocentrum, which protects the upper surface of the notochord, and below that, a larger arch-shaped intercentrum to protect the lower border. Both of these structures are embedded within a single cylindrical mass of cartilage. A similar arrangement was found in the primitive Labyrinthodonts, but in the evolutionary line that led to reptiles (and hence, also to mammals and birds), the intercentrum became partially or wholly replaced by an enlarged pleurocentrum, which in turn became the bony vertebral body.In most ray-finned fishes, including all teleosts, these two structures are fused with, and embedded within, a solid piece of bone superficially resembling the vertebral body of mammals. In living amphibians, there is simply a cylindrical piece of bone below the vertebral arch, with no trace of the separate elements present in the early tetrapods.

text: The vertebrae of

text: lobe-finned fishes

text: consist of three discrete bony elements. The vertebral arch surrounds the spinal cord, and is of broadly similar form to that found in most other vertebrates. Just beneath the arch lies a small plate-like pleurocentrum, which protects the upper surface of the

text: notochord

text: , and below that, a larger arch-shaped intercentrum to protect the lower border. Both of these structures are embedded within a single cylindrical mass of cartilage. A similar arrangement was found in the primitive

text: Labyrinthodonts

text: , but in the evolutionary line that led to reptiles (and hence, also to mammals and birds), the intercentrum became partially or wholly replaced by an enlarged pleurocentrum, which in turn became the bony vertebral body.In most

text: ray-finned fishes

text: , including all

text: teleost

text: s, these two structures are fused with, and embedded within, a solid piece of bone superficially resembling the vertebral body of mammals. In living

text: amphibian

text: s, there is simply a cylindrical piece of bone below the vertebral arch, with no trace of the separate elements present in the early tetrapods.

text: Lobe-finned fishes are a class of bony fishes called Sarcopterygii. They have fleshy, lobed, paired fins, which are joined to the body by a single bone. The fins of lobe-finned fish differ from those of all other fish in that each is borne on a fleshy, lobelike, scaly stalk extending from the body. Pectoral and pelvic fins have articulations resembling those of tetrapod limbs. These fins evolved into legs of the first tetrapod land vertebrates, amphibians. They also possess two dorsal fins with separate bases, as opposed to the single dorsal fin of ray-finned fish.

text: Lobe-finned fish

text: es are a class of

text: bony fish

text: es called Sarcopterygii. They have fleshy,

text: lobed

text: , paired fins, which are joined to the body by a single bone. The fins of lobe-finned fish differ from those of all other fish in that each is borne on a fleshy, lobelike, scaly stalk extending from the body.

text: Pectoral

text: and

text: pelvic fin

text: s have articulations resembling those of tetrapod limbs. These fins evolved into legs of the first tetrapod land vertebrates,

text: amphibian

text: ray-finned fish

text: The vertebral column surrounds the spinal cord which travels within the spinal canal, formed from a central hole within each vertebra. The spinal cord is part of the central nervous system that supplies nerves and receives information from the peripheral nervous system within the body. The spinal cord consists of grey and white matter and a central cavity, the central canal. Adjacent to each vertebra emerge spinal nerves. The spinal nerves provide sympathetic nervous supply to the body, with nerves emerging forming the sympathetic trunk and the splanchnic nerves.

text: The vertebral column surrounds the spinal cord which travels within the

text: spinal canal

text: , formed from a central hole within each

text: vertebra

text: . The spinal cord is part of the

text: central nervous system

text: that supplies nerves and receives information from the

text: peripheral nervous system

text: within the body. The spinal cord consists of

text: grey

text: and

text: white matter

text: and a central cavity, the

text: central canal

text: . Adjacent to each vertebra emerge

text: spinal nerve

text: s. The spinal nerves provide

text: sympathetic nervous supply

text: to the body, with nerves emerging forming the

text: sympathetic trunk

text: and the

text: splanchnic nerve

text: s.

text: Like all Plasmodium species P. diminutivum has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. diminutivum has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: While the term is from bacteriology, parallel examples are found throughout the tree of life. E.g. four-footed animals have evolved from piscine ancestors, yet are not generally considered fish. The four footed animals can thus be said to be "fish in disguise". In many cases, the paraphyly can be resolved by re-classifying the taxon in question under the parent group, but in bacteriology renaming groups may have serious consequences as it may cause confusion over the identity of pathogens, and is generally avoided for some groups.

text: While the term is from bacteriology, parallel examples are found throughout the

text: tree of life

text: . E.g.

text: four-footed animals

text: have evolved from piscine ancestors, yet are not generally considered

text: fish

text: . The four footed animals can thus be said to be "fish in disguise". In many cases, the paraphyly can be resolved by re-classifying the taxon in question under the parent group, but in bacteriology renaming groups may have serious consequences as it may cause confusion over the identity of

text: pathogen

text: s, and is generally avoided for some groups.

text: Olson was a former chair of the department of Biology at the UCLA,a member of the National Academy of Sciences,a recipient of Paleontological Medal of the Paleontological Society (1987), the first recipient of the Romer-Simpson Medal of the Society of Vertebrate Paleontology,  a CSEOL Distinguished Scientist (1991).University of California said that Olson "was an internationally recognized pioneer in studies of the origin and evolution of vertebrate animals".The University of Chicago said that he "carried out pioneering research on the evolution of terrestrial ecosystems".The National Academy of Science said that he ranked "among the great vertebrate paleontologists of the twentieth century".

text: Olson was a former chair of the department of Biology at the

text: UCLA

text: ,a member of the

text: National Academy of Sciences

text: ,a recipient of Paleontological Medal of the

text: Paleontological Society

text: (1987), the first recipient of the

text: Romer-Simpson Medal

text: of the Society of Vertebrate Paleontology,  a CSEOL Distinguished Scientist (1991).

text: University of California

text: said that Olson "was an internationally recognized pioneer in studies of the origin and evolution of vertebrate animals".The

text: University of Chicago

text: said that he "carried out pioneering research on the evolution of terrestrial ecosystems".The

text: National Academy of Science

text: said that he ranked "among the great vertebrate paleontologists of the twentieth century".

text: The FLMNH vertebrate fossil collections feature rich samples of all vertebrate classes, mainly from the Cenozoic Era. Included are about 400,000 specimens. Holotypes number about 200 specimens. The FLMNH vertebrate fossil collections also include the former Florida Geological Survey Collection and the UF Department of Zoology Fossil Bird Collection. Each of these collections is maintained in a separate catalog, under the acronyms UF/FGS and UF/PB, respectively. The FLMNH collections provide the most complete basis available for study of Cenozoic vertebrate paleontology in the southeastern United States and the Caribbean Basin.

text: The body and vertebral arch are ossified in the same manner as the corresponding parts in the other vertebrae, viz., one center for the body, and two for the vertebral arch.

text: The body and vertebral arch are ossified in the same manner as the corresponding parts in the other

text: vertebrae

text: , viz., one center for the body, and two for the

text: vertebral arch

text: In the spinal cord of vertebrates, commissural neurons from the dorsal regions project downward toward the ventral floor plate. Ipsilateral axons turn before reaching the floor plate to grow longitudinally, while commissural axons cross the midline and make their longitudinal turn on the contralateral side. Strikingly, Netrins, Slits, and Robos all play similar functional roles in this system as well. One outstanding mystery was the apparent lack of any comm gene in vertebrates. It now seems that at least some of Comm's functions are performed by a modified form of Robo called Robo3 (or Rig1).

text: There is a well-documented global pattern that correlates decreasing plant and animal diversity with increasing latitude, that is to say, there are fewer species as one moves towards the poles.  The cause of this pattern is one of the greatest puzzles for ecologists today.  Theories for its explanation include energy availability, climatic variability, disturbance, competition, etc. Despite this global diversity gradient, this pattern can be weak for freshwater systems compared to global marine and terrestrial systems. This may be related to size, as Hillebrand and Azovsky found that smaller organisms (protozoa and plankton) did not follow the expected trend strongly, while larger species (vertebrates) did.  They attributed this to better dispersal ability by smaller organisms, which may result in high distributions globally.

text: The life-cycles of Plasmodium species involve several different stages both in the insect and the vertebrate host. These stages include sporozoites, which are injected by the insect vector into the vertebrate host's blood. Sporozoites infect the host liver, giving rise to merozoites and (in some species) hypnozoites. These move into the blood where they infect red blood cells. In the red blood cells, the parasites can either form more merozoites to infect more red blood cells, or produce gametocytes which are taken up by insects which feed on the vertebrate host. In the insect host, gametocytes merge to sexually reproduce. After sexual reproduction, parasites grow into new sporozoites, which move to the insect's salivary glands, from which they can infect a vertebrate host bitten by the insect.

text: The life-cycles of Plasmodium species involve several different stages both in the insect and the vertebrate host. These stages include

text: sporozoite

text: s, which are injected by the insect

text: vector

text: into the vertebrate host's blood. Sporozoites infect the host liver, giving rise to

text: merozoites

text: and (in some species) hypnozoites. These move into the blood where they infect

text: red blood cells

text: . In the red blood cells, the parasites can either form more merozoites to infect more red blood cells, or produce

text: gametocytes

text: which are taken up by insects which feed on the vertebrate host. In the insect host, gametocytes merge to

text: sexually reproduce

text: . After sexual reproduction, parasites grow into new sporozoites, which move to the insect's salivary glands, from which they can infect a vertebrate host bitten by the insect.

text: Together the cranial cavity and vertebral cavity can be referred to as the dorsal body cavity.In the posterior (dorsal) cavity, the cranial cavity houses the brain, and the spinal cavity (or vertebral cavity) encloses the spinal cord. Just as the brain and spinal cord make up a continuous, uninterrupted structure, the cranial and spinal cavities that house them are also continuous. The brain and spinal cord are protected by the bones of the skull and vertebral column and by cerebrospinal fluid, a colorless fluid produced by the brain, which cushions the brain and spinal cord within the posterior (dorsal) cavity.

text: Bony fishes, class Osteichthyes, are characterised by bony skeleton rather than cartilage. They appeared in the late Silurian, about 419 million years ago. The recent discovery of Entelognathus strongly suggests that bony fishes (and possibly cartilaginous fishes, via acanthodians) evolved from early placoderms. A subclass of the Osteichthyes, the ray-finned fishes (Actinopterygii), have become the dominant group of fishes in the post-Paleozoic and modern world, with some 30,000 living species.

text: Bony fish

text: es, class Osteichthyes, are characterised by bony skeleton rather than

text: cartilage

text: . They appeared in the late

text: Silurian

text: , about 419 million years ago. The recent discovery of

text: Entelognathus

text: strongly suggests that bony fishes (and possibly cartilaginous fishes, via acanthodians) evolved from early placoderms. A subclass of the Osteichthyes, the ray-finned fishes (

text: Actinopterygii

text: ), have become the

text: dominant group

text: of fishes in the post-Paleozoic and modern world, with some 30,000 living species.

text: Beginning in 1937 Batson began a series of injection experiments investigating the anatomy and physiology of the cerebrospinal venous system. His carefully documented results demonstrated the continuity of the venous systems of the brain and the spine, as injections of contrast dyes into venous systems feeding into the spinal venous plexus led to the appearance of contrast material in the cerebral veins (Figures 5 and 7, Batson 1940). Batson noted "the extensive filling of the vertebral veins, the superior longitudinal sinus, transverse sinus as well as other dural and cerebral veins" following injection of radiopaque material into a superficial venule in the left breast (Batson 1940, Figure 5, page 143). Subsequent studies by multiple independent authors replicated Batson's findings of the continuity of the cerebral and vertebral venous systems, and the important physiological consequences of this continuity. For example, in 1996, Arnautovic et al., summarizing the results of their own work and that of others, stated: "In addition to confirming that the vertebral venous plexus is a direct continuation of the cranial venous sinuses, our study showed that it is also indirectly connected to these sinuses via the suboccipital cavernous sinus. The vertebral venous plexus is involved in regulating intracranial pressure, transmitting the influence of the respiratory and cardiac pressures to the intracranial compartment and equalizing the pressures within the venous system.". The continuity of the cerebral and vertebral venous systems was therefore essential to an understanding of both normal physiology, as well as to an understanding of the distribution of tumor metastases, as Batson had so elegantly demonstrated.

text: Beginning in 1937 Batson began a series of injection experiments investigating the anatomy and physiology of the cerebrospinal venous system. His carefully documented results demonstrated the continuity of the venous systems of the brain and the spine, as injections of

text: contrast dyes

text: into venous systems feeding into the spinal venous plexus led to the appearance of contrast material in the cerebral veins (Figures 5 and 7, Batson 1940). Batson noted "the extensive filling of the vertebral veins, the superior longitudinal sinus, transverse sinus as well as other dural and cerebral veins" following injection of radiopaque material into a superficial venule in the left breast (Batson 1940, Figure 5, page 143). Subsequent studies by multiple independent authors replicated Batson's findings of the continuity of the cerebral and vertebral venous systems, and the important physiological consequences of this continuity. For example, in 1996, Arnautovic et al., summarizing the results of their own work and that of others, stated: "In addition to confirming that the vertebral venous plexus is a direct continuation of the cranial venous sinuses, our study showed that it is also indirectly connected to these sinuses via the

text: suboccipital

text: cavernous sinus. The vertebral venous plexus is involved in regulating

text: intracranial

text: pressure, transmitting the influence of the respiratory and cardiac pressures to the intracranial compartment and equalizing the pressures within the venous system.". The continuity of the cerebral and vertebral venous systems was therefore essential to an understanding of both normal physiology, as well as to an understanding of the distribution of tumor metastases, as Batson had so elegantly demonstrated.

text: Like all Plasmodium species P. egerniae has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. egerniae has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: Cartilage is a resilient and smooth elastic tissue, rubber-like padding that covers and protects the ends of long bones at the joints, and is a structural component of the rib cage, the ear, the nose, the bronchial tubes, the intervertebral discs, and many other body components. It is not as hard and rigid as bone, but it is stiffer and less flexible than muscle.

text: Cartilage is a resilient and smooth

text: elastic tissue

text: , rubber-like padding that covers and protects the ends of long

text: bone

text: s at the

text: joint

text: s, and is a structural component of the

text: rib cage

text: , the

text: ear

text: , the

text: nose

text: , the

text: bronchial tubes

text: , the

text: intervertebral disc

text: s, and many other body components. It is not as hard and rigid as

text: bone

text: , but it is stiffer and less flexible than

text: muscle

text: Some researchers have questioned the 2R hypothesis because it predicts that vertebrate genomes should have a 4:1 gene ratio compared with invertebrate genomes, and this is not supported by findings from the 48 vertebrate genome projects available in mid-2011. For example, the human genome consists of ~21,000 protein coding genes according to June, 2011 counts at UCSC and Ensembl genome analysis centers while an average invertebrate genome size is about 15,000 genes. The amphioxus genome sequence provided support for the hypothesis of two rounds of whole genome duplication, followed by loss of duplicate copies of most genes. Additional arguments against 2R were based on the lack of the (AB)(CD) tree topology amongst four members of a gene family in vertebrates. However, if the two genome duplications occurred close together, we would not expect to find this topology. A recent study generated the sea lamprey genetic map, which yielded strong support for the hypothesis that a single whole-genome duplication occurred in the basal vertebrate lineage, preceded and followed by several evolutionarily independent segmental duplications that occurred over chordate evolution.

text: Some researchers have questioned the 2R hypothesis because it predicts that vertebrate genomes should have a 4:1 gene ratio compared with invertebrate genomes, and this is not supported by findings from the 48 vertebrate genome projects available in mid-2011. For example, the human genome consists of ~21,000 protein coding genes according to June, 2011 counts at UCSC and Ensembl genome analysis centers while an average invertebrate genome size is about 15,000 genes. The

text: amphioxus

text: genome sequence provided support for the hypothesis of two rounds of whole genome duplication, followed by loss of duplicate copies of most genes. Additional arguments against 2R were based on the lack of the (AB)(CD) tree topology amongst four members of a gene family in vertebrates. However, if the two genome duplications occurred close together, we would not expect to find this topology. A recent study generated the

text: sea lamprey

text: genetic map, which yielded strong support for the hypothesis that a single whole-genome duplication occurred in the basal vertebrate lineage, preceded and followed by several evolutionarily independent segmental duplications that occurred over chordate evolution.

text: Like all Plasmodium species P. tanzaniae has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. tanzaniae has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: If it is possible to find out what species of fish serves as the fish host for the larvae of the Carolina heelsplitters, then it will be possible to determine whether the fish host is endangered or over fished.

text: Scalzone was born in Terni, Umbria. In 1968 he came to know Franco Piperno, and on 1 March that year he took part in the clashes against Italian police at Valle Giulia. A few days later his vertebral column was seriously injured by a desk thrown from a window by neofascist students, mostly belonging to the Italian Social Movement, that were occupying the faculty of Law of the University La Sapienza in Rome. About the 1968 movement, he said:

text: Scalzone was born in

text: Terni

text: Umbria

text: . In 1968 he came to know

text: Franco Piperno

text: , and on 1 March that year he took part in the

text: clashes against Italian police at Valle Giulia

text: . A few days later his

text: vertebral column

text: was seriously injured by a

text: desk

text: thrown from a window by

text: neofascist

text: students, mostly belonging to the

text: Italian Social Movement

text: , that were occupying the faculty of Law of the University

text: La Sapienza

text: in Rome. About the 1968 movement, he said:

text: The coelacanth for example, is a marine fish. The Mesozoic coelacanth species lived in salt and fresh water. Osmoregulation in Latimeria is handled by urea retention. Urea retention is considered to indicate fresh water ancestry. This means that the coelacanth lineage evolved from freshwater to saltwater.

text: The coelacanth for example, is a marine fish. The

text: Mesozoic

text: coelacanth species lived in salt and fresh water.

text: Osmoregulation

text: in Latimeria is handled by urea retention. Urea retention is considered to indicate fresh water ancestry. This means that the coelacanth lineage evolved from freshwater to saltwater.

text: During embryonic development, tunicates exhibit determinate cleavage, where the fate of the cells is set early on with reduced cell numbers and genomes that are rapidly evolving. In contrast, the amphioxus and vertebrates show cell determination relatively late in development and cell cleavage is indeterminate. The genome evolution of amphioxus and vertebrates is also relatively slow.

text: During embryonic development, tunicates exhibit

text: determinate cleavage

text: , where the fate of the cells is set early on with reduced cell numbers and

text: genome

text: s that are rapidly evolving. In contrast, the

text: amphioxus

text: and vertebrates show

text: cell determination

text: relatively late in development and cell cleavage is indeterminate. The

text: genome evolution

text: of amphioxus and vertebrates is also relatively slow.

text: Vertebrae take their names from the regions of the vertebral column that they occupy. There are thirty-three vertebrae in the human vertebral column—seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae, five fused sacral vertebrae forming the sacrum and three to five coccygeal vertebrae, forming the coccyx. The regional vertebrae increase in size as they progress downwards but become smaller in the coccyx.

text: Vertebrae take their names from the regions of the vertebral column that they occupy. There are thirty-three vertebrae in the human vertebral column—seven

text: cervical vertebrae

text: , twelve

text: thoracic vertebrae

text: , five

text: lumbar vertebrae

text: , five fused

text: sacral vertebrae

text: forming the

text: sacrum

text: and three to five

text: coccygeal vertebrae

text: , forming the

text: coccyx

text: . The regional vertebrae increase in size as they progress downwards but become smaller in the coccyx.

text: The vertebral column consists of at least 19 presacral vertebrae, the last 6 of these being dorsals. The neural spines of the twelfth and thirteenth vertebrae form the nuchal blade, which represents the point of greatest elevation in the vertebral column.

text: The

text: vertebral column

text: consists of at least 19 presacral vertebrae, the last 6 of these being dorsals. The

text: neural spines

text: of the twelfth and thirteenth vertebrae form the nuchal blade, which represents the point of greatest elevation in the vertebral column.

text: An evolutionary timeline of the late Devonian vertebrate terrestrial invasion demonstrates the changes that took place. A group of fish from the Givetian stage began developing limbs, and eventually evolved into aquatic tetrapods in the Famennian stage. Pederpes, Westlothiana, Protogyrinus, and Crassigyrinus descended from these species into the carboniferous period and were the first land vertebrates.

text: An evolutionary timeline of the late Devonian vertebrate terrestrial invasion demonstrates the changes that took place. A group of fish from the

text: Givetian

text: stage began developing limbs, and eventually evolved into aquatic tetrapods in the

text: Famennian

text: stage. Pederpes, Westlothiana, Protogyrinus, and Crassigyrinus descended from these species into the carboniferous period and were the first land vertebrates.

text: Like all species in this genus it has both vertebrate and insect hosts. The vertebrate host are reptiles.

text: vertebrate

text: and

text: insect

text: hosts. The vertebrate host are

text: reptile

text: s.

text: In early fish and in chondrichthyans (cartilaginous fish such as sharks), the Meckelian Cartilage continued to be the main component of the lower jaw. But in the adult forms of osteichthyans (bony fish) and their descendants (amphibians, reptiles, birds, mammals), the cartilage was covered in bone - although in their embryos the jaw initially develops as the Meckelian Cartilage. In all tetrapods the cartilage partially ossifies (changes to bone) at the rear end of the jaw and becomes the articular bone, which forms part of the jaw joint in all tetrapods except mammals.

text: In early fish and in

text: chondrichthyans

text: (cartilaginous fish such as

text: shark

text: s), the Meckelian Cartilage continued to be the main component of the lower jaw. But in the adult forms of

text: osteichthyans

text: (bony fish) and their descendants (

text: amphibians

text: reptiles

text: birds

text: mammals

text: ), the cartilage was covered in bone - although in their

text: embryos

text: the jaw initially develops as the Meckelian Cartilage. In all

text: tetrapods

text: the cartilage partially ossifies (changes to bone) at the rear end of the jaw and becomes the

text: articular

text: bone, which forms part of the jaw joint in all tetrapods except

text: mammals

text: The main radiographic features of generalized osteoporosis are cortical thinning and increased radiolucency. Frequent complications of osteoporosis are vertebral fractures for which spinal radiography can help considerably in diagnosis and follow-up. Vertebral height measurements can objectively be made using plain-film X-rays by using several methods such as height loss together with area reduction, particularly when looking at vertical deformity in T4-L4, or by determining a spinal fracture index that takes into account the number of vertebrae involved. Involvement of multiple vertebral bodies leads to kyphosis of the thoracic spine, leading to what is known as dowager's hump.

text: The main radiographic features of generalized osteoporosis are cortical thinning and increased radiolucency. Frequent complications of osteoporosis are vertebral fractures for which spinal radiography can help considerably in diagnosis and follow-up. Vertebral height measurements can objectively be made using plain-film X-rays by using several methods such as height loss together with area reduction, particularly when looking at vertical deformity in T4-L4, or by determining a spinal fracture index that takes into account the number of vertebrae involved. Involvement of multiple vertebral bodies leads to kyphosis of the thoracic spine, leading to what is known as

text: dowager's hump

text: The smallest vertebrates (and smallest amphibians) known are Paedophryne amauensis frogs from Papua New Guinea, which range in length from , and average . Previously, the title of smallest vertebrate was held by members of the fish genus Paedocypris of Indonesia.

text: The smallest

text: vertebrate

text: s (and smallest amphibians) known are

text: Paedophryne amauensis

text: frogs from Papua New Guinea, which range in length from , and average . Previously, the title of smallest vertebrate was held by members of the fish

text: genus

text: Paedocypris

text: of

text: Indonesia

text: Evolution of the Vertebrates, subtitled "A History of the Backboned Animals Through Time" is a basic paleontology textbook by Edwin H. Colbert, published by John Wiley & Sons.

text: Evolution of the Vertebrates, subtitled "A History of the Backboned Animals Through Time" is a basic paleontology

text: textbook

text: by

text: Edwin H. Colbert

text: , published by

text: John Wiley & Sons

text: Operant studies using vertebrates have been conducted for many years. In such studies, an animal operates or changes some part of the environment to gain a positive reinforcement or avoid a negative one. In this way, animals learn from the consequence of their own actions, i.e. they use an internal predictor. Operant responses indicate a voluntary act; the animal exerts control over the frequency or intensity of its responses, making these distinct from reflexes and complex fixed action patterns. A number of studies have revealed surprising similarities between vertebrates and invertebrates in their capacity to use operant responses to gain positive reinforcements, but also to avoid negative reinforcement that in vertebrates would be described as 'pain'.

text: Operant studies

text: using vertebrates have been conducted for many years. In such studies, an animal operates or changes some part of the environment to gain a positive

text: reinforcement

text: or avoid a negative one. In this way, animals learn from the consequence of their own actions, i.e. they use an internal predictor. Operant responses indicate a voluntary act; the animal exerts control over the frequency or intensity of its responses, making these distinct from reflexes and complex

text: fixed action pattern

text: s. A number of studies have revealed surprising similarities between vertebrates and invertebrates in their capacity to use operant responses to gain positive reinforcements, but also to avoid negative reinforcement that in vertebrates would be described as 'pain'.

text: In the fetus, vertebral segments correspond with spinal cord segments. However, because the vertebral column grows longer than the spinal cord, spinal cord segments do not correspond to vertebral segments in the adult, particularly in the lower spinal cord. For example, lumbar and sacral spinal cord segments are found between vertebral levels T9 and L2, and the spinal cord ends around the L1/L2 vertebral level, forming a structure known as the conus medullaris.

text: In 1999, Garvey completed a Bachelor of Arts/Bachelor of Science (Hons) with a joint thesis between the Departments of Archaeology and Zoology at La Trobe University. The focus of her thesis was in identifying the fossilized history of a late Holocene assemblage of small mammals in Tasmania. This project involved studying the dietary selectivity of predators and "included the role in which Strigiformes (owls) play in the accumulation of small animals in these faunal assemblages". "Experimental feeding trials of the three owl taxa known to currently inhabit Tasmania" were conducted as part of the research in the investigation of regurgitated owl-pellets in determining the source of small animal bones. In 2005, her PhD in Palaeontology  "investigated the vertebrate taphonomy, palaeoecology and the depositional environment of an Early Carboniferous (Tournaisian) fossil fish locality, Fish Hill, in the Home Station Member of the Snowy Plains Formation, Mansfield Basin, Australia. This project combined research on the vertebrate fish assemblage, micro vertebrates, ichnology, taphonomy and geology of the locality to develop an overall understanding of the palaeoecology and palaeocommunity". Research from her thesis contributed to increase knowledge on new fish species from the Early Carboniferous in the Mansfield Basin locality.

text: Certain fish also evolved to breathe air to survive oxygen-deprived water, such as arapaima (family Osteoglossidae) and walking catfish.

text: Certain

text: fish

text: also evolved to breathe air to survive oxygen-deprived water, such as

text: arapaima

text: (family

text: Osteoglossidae

text: ) and

text: walking catfish

text: Catfish belong to a superorder called the Ostariophysi, which also includes the Cypriniformes, Characiformes, Gonorynchiformes and Gymnotiformes, a superorder characterized by the Weberian apparatus. Some place Gymnotiformes as a sub-order of Siluriformes, however this is not as widely accepted. Currently, the Siluriformes are said to be the sister group to the Gymnotiformes, though this has been debated due to more recent molecular evidence.  there are about 36 extant catfish families, and about 3,093 extant species have been described. This makes the catfish order the second or third most diverse vertebrate order; in fact, 1 out of every 20 vertebrate species is a catfish.

text: Catfish belong to a superorder called the

text: Ostariophysi

text: , which also includes the

text: Cypriniformes

text: Characiformes

text: Gonorynchiformes

text: and

text: Gymnotiformes

text: , a superorder characterized by the

text: Weberian apparatus

text: . Some place Gymnotiformes as a sub-order of Siluriformes, however this is not as widely accepted. Currently, the Siluriformes are said to be the

text: sister group

text: to the Gymnotiformes, though this has been debated due to more recent molecular evidence.  there are about 36

text: extant

text: catfish families, and about 3,093 extant species have been described. This makes the catfish order the second or third most diverse

text: vertebrate

text: order; in fact, 1 out of every 20 vertebrate species is a catfish.

text: The surgeon replaces missing parts with tissue of like quality and quantity; nasal lining with mucosa, cartilage with cartilage, bone with bone, and skin with skin that best match the native skin color and skin texture of the damaged nasal subunit. For such surgical repairs, skin flaps are preferable to skin grafts, because skin flaps generally are the superior remedy for matching the color and the texture of nasal skin, better resist tissue contracture, and provide better vascularisation of the nasal skeleton; thus, when there is sufficient skin to allow tissue harvesting, nasal skin is the best source of nasal skin. Furthermore, despite its notable scarring propensity, the nasal skin flap is the prime consideration for nasal reconstruction, because of its greater verisimilitude.

text: The surgeon replaces missing parts with tissue of like quality and quantity; nasal lining with

text: mucosa

text: , cartilage with cartilage, bone with bone, and skin with skin that best match the native skin color and skin texture of the damaged nasal subunit. For such surgical repairs, skin flaps are preferable to skin grafts, because skin flaps generally are the superior remedy for matching the color and the texture of nasal skin, better resist tissue contracture, and provide better vascularisation of the nasal skeleton; thus, when there is sufficient skin to allow tissue harvesting, nasal skin is the best source of nasal skin. Furthermore, despite its notable

text: scar

text: ring propensity, the nasal skin flap is the prime consideration for nasal reconstruction, because of its greater verisimilitude.

text: Vertebrate paleozoology refers to the use of morphological, temporal, and stratigraphic data to map vertebrate history in evolutionary theory. Vertebrates are classified as a subphylum of Chordata, a phylum used to classify species adhering to a rod-shaped, flexible body type called a notochord. They differ from other phyla in that other phyla may have cartilage or cartilage-like tissues forming a sort of skeleton, but only vertebrates possess what we define as bone.

text: It includes the prevertebral muscles (longus colli and longus capitis), vertebral artery, vertebral vein, scalene muscles, phrenic nerve and part of the brachial plexus.

text: It includes the

text: prevertebral muscles

text: longus colli

text: and

text: longus capitis

text: vertebral artery

text: vertebral vein

text: scalene muscle

text: s,

text: phrenic nerve

text: and part of the

text: brachial plexus

text: Cranial nerves are also present in other vertebrates. Other amniotes (non-amphibian tetrapods) have cranial nerves similar to those of humans.  In anamniotes (fishes and amphibians), the accessory nerve (XI) and hypoglossal nerve (XII) do not exist, with the accessory nerve (XI) being an integral part of the vagus nerve (X); the hypoglossal nerve (XII) is represented by a variable number of spinal nerves emerging from vertebral segments fused into the occiput. These two nerves only became discrete nerves in the ancestors of amniotes (non-amphibian tetrapods).

text: Cranial nerves are also present in other

text: vertebrate

text: s. Other

text: amniote

text: s (non-amphibian tetrapods) have cranial nerves similar to those of humans.  In

text: anamniote

text: s (fishes and amphibians), the accessory nerve (XI) and hypoglossal nerve (XII) do not exist, with the accessory nerve (XI) being an integral part of the vagus nerve (X); the hypoglossal nerve (XII) is represented by a variable number of spinal nerves emerging from vertebral segments fused into the occiput. These two nerves only became discrete nerves in the ancestors of

text: amniote

text: s (non-amphibian tetrapods).

text: The horse skeleton averages 205 bones. A significant difference between the horse skeleton and that of a human is the lack of a collarbone—the horse's forelimbs are attached to the spinal column by a powerful set of muscles, tendons, and ligaments that attach the shoulder blade to the torso. The horse's legs and hooves are also unique structures. Their leg bones are proportioned differently from those of a human. For example, the body part that is called a horse's "knee" is actually made up of the carpal bones that correspond to the human wrist. Similarly, the hock contains bones equivalent to those in the human ankle and heel. The lower leg bones of a horse correspond to the bones of the human hand or foot, and the fetlock (incorrectly called the "ankle") is actually the proximal sesamoid bones between the cannon bones (a single equivalent to the human metacarpal or metatarsal bones) and the proximal phalanges, located where one finds the "knuckles" of a human. A horse also has no muscles in its legs below the knees and hocks, only skin, hair, bone, tendons, ligaments, cartilage, and the assorted specialized tissues that make up the hoof.

text: The horse skeleton averages 205 bones. A significant difference between the horse skeleton and that of a human is the lack of a

text: collarbone

text: —the horse's

text: forelimbs

text: are attached to the

text: spinal column

text: by a powerful set of muscles, tendons, and ligaments that attach the

text: shoulder blade

text: to the torso. The horse's legs and hooves are also unique structures. Their leg bones are proportioned differently from those of a human. For example, the body part that is called a horse's "knee" is actually made up of the

text: carpal

text: bones that correspond to the human

text: wrist

text: . Similarly, the

text: hock

text: contains bones equivalent to those in the human

text: ankle

text: and

text: heel

text: . The lower leg bones of a horse correspond to the bones of the human hand or foot, and the

text: fetlock

text: (incorrectly called the "ankle") is actually the proximal

text: sesamoid bone

text: s between the

text: cannon

text: bones (a single equivalent to the human

text: metacarpal

text: or

text: metatarsal

text: bones) and the

text: proximal phalanges

text: , located where one finds the "knuckles" of a human. A horse also has no muscles in its legs below the knees and hocks, only skin, hair, bone,

text: tendon

text: s,

text: ligament

text: s,

text: cartilage

text: , and the assorted specialized tissues that make up the

text: hoof

text: Visits to Banksia inflorescences by western honeybees and nectariferous birds are often observed and are obviously important to pollination. Also important are visits by nectariferous mammals, although such visits are rarely observed because these mammals are usually nocturnal and reclusive. Studies have found that Banksia inflorescences are foraged by a variety of small mammals, including marsupials (such as possums and yellow-footed antechinus, Antechinus flavipes), and rodents (such as the pale field rat, Rattus tunneyi). These carry pollen loads comparable to those of nectariferous birds, making them effective pollinators. Other studies have shown that the relative importance of vertebrates and invertebrates for pollination may vary from species to species, with some Banksia species exhibiting reduced fruit set when vertebrate pollinators are excluded, while others are unaffected by the exclusion of vertebrates and set some fruit even when all pollinators are excluded.

text: Visits to Banksia inflorescences by

text: western honeybee

text: s and nectariferous

text: bird

text: s are often observed and are obviously important to pollination. Also important are visits by nectariferous mammals, although such visits are rarely observed because these mammals are usually

text: nocturnal

text: and reclusive. Studies have found that Banksia inflorescences are foraged by a variety of small mammals, including

text: marsupial

text: s (such as

text: possums

text: and

text: yellow-footed antechinus

text: , Antechinus flavipes), and

text: rodent

text: s (such as the

text: pale field rat

text: , Rattus tunneyi). These carry pollen loads comparable to those of nectariferous birds, making them effective pollinators. Other studies have shown that the relative importance of

text: vertebrate

text: s and

text: invertebrate

text: s for pollination may vary from species to species, with some Banksia species exhibiting reduced fruit set when vertebrate pollinators are excluded, while others are unaffected by the exclusion of vertebrates and set some fruit even when all pollinators are excluded.

text: He studied physiology at London University and went on to study history of science and vertebrate palaeontology at University College London before researching the history of vertebrate palaeontology at Harvard University. He was awarded a Ph.D. in the area of the  Victorian-period context of Darwinian evolution.

text: He studied physiology at

text: London University

text: and went on to study history of science and vertebrate palaeontology at

text: University College London

text: before researching the history of vertebrate palaeontology at

text: Harvard University

text: . He was awarded a Ph.D. in the area of the  Victorian-period context of Darwinian evolution.

text: Those supporting a convergent evolution state that this common ancestor would have preceded both cephalopods and vertebrates by a significant margin. The common ancestor with the expression for camera-type eye would have existed approximately 270 million years before the evolution of camera-type eye in cephalopods and approximately 110 to 260 million years before the evolution of camera-type eye in vertebrates. Another source of evidence for this is the differences of expression due to independent variants of Pax6 arising in both cephalopods and vertebrates. Cephalopods contain five variants of Pax6 in their genomes which independently arose and are not shared by vertebrates, although they allow for a similar gene expression when compared to the Pax6 of vertebrates.

text: Facultative parthenogenesis is the type of parthenogenesis when a female individual can reproduce via both sexual and asexual reproduction. Females can produce viable offspring with or without genetic contribution from a male, and such an ability may, just like true parthenogens, enable colonization of new habitats by single female animals. Facultative parthenogenesis is extremely rare in nature, with only a few examples of animal taxa capable of facultative parthenogenesis, of which none are vertebrate taxa.

text: :"Bristlemouth" redirects here. This name is also used to refer to some of the related Sternoptychidae, namely the genus Argyripnus.The Gonostomatidae are a family of mesopelagic marine fish, commonly named bristlemouths, lightfishes, or anglemouths. It is a relatively small family, containing only eight known genera and 32 species. However, bristlemouths make up for their lack of diversity with numbers: Cyclothone, with 12 species, is thought to be (along with Vinciguerria), the most abundant vertebrate genus in the world, numbering in the hundreds of trillions to quadrillions.

text: :"Bristlemouth" redirects here. This name is also used to refer to some of the related

text: Sternoptychidae

text: , namely the

text: genus

text: Argyripnus

text: .The Gonostomatidae are a family of

text: mesopelagic

text: marine fish, commonly named bristlemouths, lightfishes, or anglemouths. It is a relatively small

text: family

text: , containing only eight known

text: genera

text: and 32

text: species

text: . However, bristlemouths make up for their lack of diversity with numbers:

text: Cyclothone

text: , with 12 species, is thought to be (along with

text: Vinciguerria

text: ), the most abundant vertebrate genus in the world, numbering in the hundreds of

text: trillions

text: to

text: quadrillion

text: s.

text: The endoskeletons of echinoderms and some other soft-bodied invertebrates such as jellyfish and earthworms are also termed hydrostatic; a body cavity the coelom is filled with coelomic fluid and the pressure from this fluid acts together with the surrounding muscles to change the organism's shape and produce movement.

text: The endoskeletons of echinoderms and some other soft-bodied

text: invertebrate

text: s such as

text: jellyfish

text: and

text: earthworms

text: are also termed

text: hydrostatic

text: ; a body cavity the

text: coelom

text: is filled with

text: coelomic fluid

text: and the pressure from this fluid acts together with the surrounding muscles to change the organism's shape and produce movement.

text: The scientific classification of acanthodians is still a subject of great dispute, due to the fact that they share qualities of both bony fish (osteichthyes) and cartilaginous fish (chondrichthyes). A recent study has suggested that Acanthodes may have been, or closely related to an early common ancestor to all cartilaginous and bony fish, including humans. Acanthodian internal anatomy is primarily understood by Acanthodes bronni because it remains the only example preserved in substantial detail, central to which is an osensible osteichthyan braincase. For this reason, Acanthodes has become an indispensable component in early gnathostome phylogenies. Acanthodes is quantifiably closer to chondrichthyans than to osteichthyans. However, phylogenetic analysis places Acanthodes on the osteichthyan stem, as part of a well-resolved tree that also recovers acanthodians as stem chondrichthyans and stem gnathostomes. As such, perceived chondrichthyan features of the Acanthodes cranium represent shared primitive conditions for crown group gnathostomes. There has been increasingly detailed findings of early gnathostome evolution highlights ongoing and profound anatomical reorganization of vertebrate crania after the origin of jaws but before the divergence of living clades.

text: The scientific classification of acanthodians is still a subject of great dispute, due to the fact that they share qualities of both bony fish (

text: osteichthyes

text: ) and cartilaginous fish (

text: chondrichthyes

text: ). A recent study has suggested that Acanthodes may have been, or closely related to an early common ancestor to all

text: cartilaginous

text: and

text: bony fish

text: , including

text: humans

text: Acanthodian

text: internal anatomy is primarily understood by Acanthodes bronni because it remains the only example preserved in substantial detail, central to which is an osensible

text: osteichthyan

text: braincase. For this reason, Acanthodes has become an indispensable component in early gnathostome phylogenies. Acanthodes is quantifiably closer to

text: chondrichthyans

text: than to

text: osteichthyan

text: s. However, phylogenetic analysis places Acanthodes on the osteichthyan stem, as part of a well-resolved tree that also recovers acanthodians as stem chondrichthyans and stem

text: gnathostomes

text: . As such, perceived chondrichthyan features of the Acanthodes cranium represent shared primitive conditions for crown group gnathostomes. There has been increasingly detailed findings of early gnathostome evolution highlights ongoing and profound anatomical reorganization of vertebrate crania after the origin of

text: jaw

text: s but before the divergence of living clades.

text: The shoulder blades were long flat blade-like bones, held roughly parallel to the vertebral column. The hips were composed of three elements each: an elongate ilium above the articulation with the leg, an ischium below and behind with a long thin rod, and a pubis in front that flared into a plate-like structure. The structure of the hip hindered the animal from standing with its back erect, because in such a position the thigh bone would have pushed against the joint of the ilium and pubis, instead of pushing only against the solid ilium.  The nine fused hip vertebrae provided support for the hip.

text: The

text: shoulder blades

text: were long flat blade-like bones, held roughly parallel to the vertebral column. The

text: hips

text: were composed of three elements each: an elongate

text: ilium

text: above the articulation with the leg, an

text: ischium

text: below and behind with a long thin rod, and a

text: pubis

text: in front that flared into a plate-like structure. The structure of the hip hindered the animal from standing with its back erect, because in such a position the

text: thigh bone

text: would have pushed against the joint of the ilium and pubis, instead of pushing only against the solid ilium.  The nine fused hip vertebrae provided support for the hip.

text: The WICGR has also made a leading contribution to the sequencing of the mouse genome. Aside from academic interest this is an important step in fully understanding the molecular biology of mice which are often used as model organisms in studies of everything from human diseases to embryonic development. Increased understanding of mice will thus facilitate many areas of research. The WICGR has also sequenced the genomes of Ciona savignyi (sea squirt), the pufferfish, the filamentous fungus Neurospora crassa, and multiple relatives of Saccharomyces cerevisiae, one of the most studied yeasts. The Ciona savignyi genome provides a good system for exploring the evolutionary origins of all vertebrates. Pufferfish have smaller-sized genomes compared to other vertebrates; as a result, their genomes are "mini" models for vertebrates. The sequencing of the yeasts related to Saccharomyces cerevisiae will ease the identification of key gene regulatory elements some of which may be common to all eukaryotes (including both plant and animal kingdoms).

text: The WICGR has also made a leading contribution to the sequencing of the mouse genome. Aside from academic interest this is an important step in fully understanding the molecular biology of mice which are often used as model organisms in studies of everything from human diseases to embryonic development. Increased understanding of mice will thus facilitate many areas of research. The WICGR has also sequenced the genomes of

text: Ciona savignyi

text: (sea squirt), the

text: pufferfish

text: , the

text: filamentous

text: fungus

text: Neurospora crassa

text: , and multiple relatives of

text: Saccharomyces cerevisiae

text: , one of the most studied

text: yeast

text: s. The Ciona savignyi genome provides a good system for exploring the evolutionary origins of all

text: vertebrate

text: s. Pufferfish have smaller-sized genomes compared to other vertebrates; as a result, their genomes are "mini" models for vertebrates. The sequencing of the yeasts related to Saccharomyces cerevisiae will ease the identification of key gene regulatory elements some of which may be common to all

text: eukaryote

text: s (including both plant and animal kingdoms).

text: Nearly all mammals are endothermic ("warm-blooded"). Most mammals also have hair to help keep them warm. Like birds, mammals can forage or hunt in weather and climates too cold for ectothermic ("cold-blooded") reptiles and insects. Endothermy requires plenty of food energy, so mammals eat more food per unit of body weight than most reptiles. Small insectivorous mammals eat prodigious amounts for their size. A rare exception, the naked mole-rat produces little metabolic heat, so it is considered an operational poikilotherm. Birds are also endothermic, so endothermy is not unique to mammals.

text: Nearly all mammals are

text: endothermic

text: ("warm-blooded"). Most mammals also have hair to help keep them warm. Like birds, mammals can forage or hunt in weather and climates too cold for

text: ectotherm

text: ic ("cold-blooded") reptiles and insects. Endothermy requires plenty of food energy, so mammals eat more food per unit of body weight than most reptiles. Small insectivorous mammals eat prodigious amounts for their size. A rare exception, the

text: naked mole-rat

text: produces little metabolic heat, so it is considered an operational

text: poikilotherm

text: . Birds are also endothermic, so endothermy is not unique to mammals.

text: The striking segmented pattern of the spine is established during embryogenesis when somites are rhythmically added to the posterior of the embryo. Somite formation begins around the third week when the embryo begins gastrulation and continues until around 52 somites are formed. The somites are spheres, formed from the paraxial mesoderm that lies at the sides of the neural tube and they contain the precursors of spinal bone, the vertebrae ribs and some of the skull, as well as muscle, ligaments and skin. Somitogenesis and the subsequent distribution of somites is controlled by a clock and wavefront model acting in cells of the paraxial mesoderm. Soon after their formation, sclerotomes, which give rise to some of the bone of the skull, the vertebrae and ribs, migrate, leaving the remainder of the somite now termed a dermamyotome behind. This then splits to give the myotomes which will form the muscles and dermatomes which will form the skin of the back.  Sclerotomes become subdivided into an anterior and a posterior compartment. This subdivision plays a key role in the definitive patterning of vertebrae that form when the posterior part of one somite fuses to the anterior part of the consecutive somite during a process termed resegmentation. Disruption of the somitogenesis process in humans results in diseases such as congenital scoliosis. So  far, the human homologues of three genes associated to the mouse segmentation clock, (MESP2, DLL3 and LFNG), have been shown to be mutated in cases of congenital scoliosis, suggesting that the mechanisms involved in vertebral segmentation are conserved across vertebrates. In humans the first four somites are incorporated in the base of the occipital bone of the skull and the next 33 somites will form the vertebrae, ribs, muscles, ligaments and skin. The remaining posterior somites degenerate. During the fourth week of embryogenesis, the sclerotomes shift their position to surround the spinal cord and the notochord. This column of tissue has a segmented appearance, with alternating areas of dense and less dense areas.

text: The striking

text: segmented

text: pattern of the spine is established during

text: embryogenesis

text: when

text: somites

text: are rhythmically added to the posterior of the embryo. Somite formation begins around the third week when the embryo begins

text: gastrulation

text: and continues until around 52 somites are formed. The somites are spheres, formed from the

text: paraxial mesoderm

text: that lies at the sides of the neural tube and they contain the precursors of spinal bone, the vertebrae ribs and some of the skull, as well as muscle, ligaments and skin.

text: Somitogenesis

text: and the subsequent distribution of somites is controlled by a

text: clock and wavefront model

text: acting in cells of the paraxial mesoderm. Soon after their formation,

text: sclerotome

text: s, which give rise to some of the bone of the skull, the vertebrae and ribs, migrate, leaving the remainder of the somite now termed a dermamyotome behind. This then splits to give the

text: myotomes

text: which will form the muscles and

text: dermatome

text: s which will form the skin of the back.  Sclerotomes become subdivided into an anterior and a posterior compartment. This subdivision plays a key role in the definitive patterning of vertebrae that form when the posterior part of one somite fuses to the anterior part of the consecutive somite during a process termed resegmentation. Disruption of the somitogenesis process in humans results in diseases such as congenital scoliosis. So  far, the human homologues of three genes associated to the mouse segmentation clock, (MESP2, DLL3 and LFNG), have been shown to be mutated in cases of congenital scoliosis, suggesting that the mechanisms involved in vertebral segmentation are conserved across vertebrates. In humans the first four somites are incorporated in the base of the

text: occipital bone

text: of the skull and the next 33 somites will form the vertebrae, ribs, muscles, ligaments and skin. The remaining posterior somites degenerate. During the fourth week of

text: embryogenesis

text: , the

text: sclerotome

text: s shift their position to surround the

text: spinal cord

text: and the

text: notochord

text: . This column of tissue has a segmented appearance, with alternating areas of dense and less dense areas.

text: In order for bones to attain their normal shape and size, they require the stresses from normal musculature. Osseous findings will, therefore, mirror the specific muscular deficits in a given person with CP. The shafts of the bones are often thin (gracile) and become thinner during growth. When compared to these thin shafts (diaphyses), the centres (metaphyses) often appear quite enlarged (ballooning). With a lack of use, articular cartilage may atrophy, leading to narrowed joint spaces. Depending on the degree of spasticity, a person with CP may exhibit a variety of angular joint deformities. Because vertebral bodies need vertical gravitational loading forces to develop properly, spasticity and an abnormal gait can hinder proper and/or full bone and skeletal development. People with CP tend to be shorter in height than the average person because their bones are not allowed to grow to their full potential. Sometimes bones grow to different lengths, so the person may have one leg longer than the other.

text: In order for bones to attain their normal shape and size, they require the stresses from normal musculature. Osseous findings will, therefore, mirror the specific muscular deficits in a given person with CP. The shafts of the bones are often thin (gracile) and become thinner during growth. When compared to these thin shafts (

text: diaphyses

text: ), the centres (

text: metaphyses

text: ) often appear quite enlarged (ballooning). With a lack of use, articular cartilage may atrophy, leading to narrowed joint spaces. Depending on the degree of spasticity, a person with CP may exhibit a variety of angular joint deformities. Because vertebral bodies need vertical gravitational loading forces to develop properly, spasticity and an abnormal gait can hinder proper and/or full bone and skeletal development. People with CP tend to be shorter in height than the average person because their bones are not allowed to grow to their full potential. Sometimes bones grow to different lengths, so the person may have one leg longer than the other.

text: Like all Plasmodium species P. audaciosum has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. audaciosum has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: Similar to the laryngeal nerve in giraffes, the vas deferens is part of the male anatomy of many vertebrates; it transports sperm from the epididymis in anticipation of ejaculation. In humans, the vas deferens routes up from the testicle, looping over the ureter, and back down to the urethra and penis. It has been suggested that this is due to the descent of the testicles during the course of human evolution—likely associated with temperature. As the testicles descended, the vas deferens lengthened to accommodate the accidental "hook" over the ureter.

text: Similar to the laryngeal nerve in giraffes, the

text: vas deferens

text: is part of the

text: male anatomy

text: of many

text: vertebrates

text: ; it transports sperm from the

text: epididymis

text: in anticipation of

text: ejaculation

text: . In humans, the vas deferens routes up from the

text: testicle

text: , looping over the

text: ureter

text: , and back down to the

text: urethra

text: and

text: penis

text: . It has been suggested that this is due to the descent of the testicles during the course of human evolution—likely associated with temperature. As the testicles descended, the vas deferens lengthened to accommodate the accidental "hook" over the ureter.

text: Compared with other vertebrates, birds have a body plan that shows many unusual adaptations, mostly to facilitate flight.

text: Compared with other vertebrates, birds have a

text: body plan

text: that shows many unusual adaptations, mostly to facilitate

text: flight

text: The only known specimen of Gerobatrachus is a nearly complete skeleton about  long. It is preserved in red siltstone with only its underside exposed. Like other amphibamid temnospondyls, Gerobatrachus has a rounded and flattened head, well-developed limbs, and a small tail. Its vertebral column is somewhat shorter than those of related amphibamids. The large, round head and shortened vertebral column are features Gerobatrachus shares in common with frogs and the early salamander Karaurus. Gerobatrachus also has a large embayment at the back of the skull called an otic notch, which is seen other amphibamids and in frogs and supports the tympanum, an eardrum-like structure used in hearing.

text: The only known specimen of Gerobatrachus is a nearly complete skeleton about  long. It is preserved in red

text: siltstone

text: with only its underside exposed. Like other amphibamid temnospondyls, Gerobatrachus has a rounded and flattened head, well-developed limbs, and a small tail. Its vertebral column is somewhat shorter than those of related amphibamids. The large, round head and shortened vertebral column are features Gerobatrachus shares in common with frogs and the early salamander

text: Karaurus

text: . Gerobatrachus also has a large embayment at the back of the skull called an

text: otic notch

text: , which is seen other amphibamids and in frogs and supports the

text: tympanum

text: , an eardrum-like structure used in hearing.

text: L. alexandri is a rarely imported aquarium fish. These fish require a sandy substrate and should not be maintained with fish that it can eat (a fish less than half of its size).

text: L. alexandri is a rarely imported

text: aquarium

text: fish. These fish require a sandy

text: substrate

text: and should not be maintained with fish that it can eat (a fish less than half of its size).

text: Opponents of catch and release point out that fish are highly evolved vertebrates that share many of the same neurological structures that, in humans, are associated with pain perception. They point to studies that show that, neurologically, fish are quite similar to so-called higher vertebrates and that blood chemistry reveals that hormones and blood metabolites associated with stress are quite high in fish struggling against hook and line. The idea that fish do not feel pain in their mouths has been studied at the University of Edinburgh and the Roslin Institute by injecting bee venom and acetic acid into the lips of rainbow trout; the fish responded by rubbing their lips along the sides and floors of their tanks in an effort to relieve themselves of the sensation. Lead researcher Dr. Lynne Sneddon wrote, "Our research demonstrates nociception and suggests that noxious stimulation in the rainbow trout has adverse behavioral and physiological effects. This fulfils the criteria for animal pain." A recent (2014) paper provides a critique of existing studies that purport to demonstrate that fish feel pain.

text: Opponents of catch and release point out that fish are highly evolved

text: vertebrates

text: that share many of the same neurological structures that, in humans, are associated with

text: pain perception

text: . They point to studies that show that, neurologically, fish are quite similar to so-called

text: higher vertebrates

text: and that blood chemistry reveals that hormones and blood metabolites associated with stress are quite high in fish struggling against hook and line. The idea that fish do not feel pain in their mouths has been studied at the

text: University of Edinburgh

text: and the

text: Roslin Institute

text: by injecting bee venom and acetic acid into the lips of rainbow trout; the fish responded by rubbing their lips along the sides and floors of their tanks in an effort to relieve themselves of the sensation. Lead researcher Dr. Lynne Sneddon wrote, "Our research demonstrates nociception and suggests that noxious stimulation in the rainbow trout has adverse behavioral and physiological effects. This fulfils the criteria for animal pain." A recent (2014) paper provides a critique of existing studies that purport to demonstrate that fish feel pain.

text: The device itself was a stainless steel distraction rod fitted with hooks at both ends and a ratchet and was implanted through an extensive posterior spinal approach, the hooks being secured onto the vertebral laminae. It was used at the beginning without performing a spinal fusion but early results proved fusion as part of the procedure was mandatory, as movement of the unfused spine would cause the metal to fatigue and eventually break. The procedure required the use of a postoperative plaster cast or bracing until vertebral fusion had occurred.

text: The device itself was a stainless steel distraction rod fitted with hooks at both ends and a ratchet and was implanted through an extensive

text: posterior

text: spinal approach, the hooks being secured onto the

text: vertebral

text: laminae

text: . It was used at the beginning without performing a

text: spinal fusion

text: but early results proved fusion as part of the procedure was mandatory, as movement of the unfused spine would cause the metal to fatigue and eventually break. The procedure required the use of a postoperative plaster cast or bracing until vertebral fusion had occurred.

text: References to Arthromitus date back to 1849, when they were first observed by renowned physician and naturalist Joseph Leidy, who named the organisms Arthromitus (from Greek Arthro-, joint + mitos, thread). The filamentous morphology of the original Arthromitus was thought to be so unique that similar filaments observed in the vertebrate guts were erroneously placed under the division Candidatus Arthromitus. However, 16S rRNA-based phylogeny revealed the Arthromitus filaments, first observed by Leidy in arthropod guts, to belong to a group within the Lachnospiraceae, making them quite distant from previously observed filamentous organisms from vertebrate guts. These isomorphic bacteria from vertebrates were hence moved to a new division designated Candidatus Savagella. A poorly designed set of experiments aimed at isolating Arthromitus from termite guts led to the conclusion that Arthromitus is in fact a growth stage of Bacillus cereus. This mistaken finding was later disproved when the true identity of Arthromitus was confirmed.

text: References to Arthromitus date back to 1849, when they were first observed by renowned physician and naturalist

text: Joseph Leidy

text: , who named the organisms Arthromitus (from Greek Arthro-, joint + mitos, thread). The filamentous morphology of the original Arthromitus was thought to be so unique that similar filaments observed in the vertebrate guts were erroneously placed under the division Candidatus Arthromitus. However, 16S rRNA-based phylogeny revealed the Arthromitus filaments, first observed by Leidy in arthropod guts, to belong to a group within the Lachnospiraceae, making them quite distant from previously observed filamentous organisms from vertebrate guts. These isomorphic bacteria from vertebrates were hence moved to a new division designated

text: Candidatus Savagella

text: . A poorly designed set of experiments aimed at isolating Arthromitus from termite guts led to the conclusion that Arthromitus is in fact a growth stage of Bacillus cereus. This mistaken finding was later disproved when the true identity of Arthromitus was confirmed.

text: The Society of Vertebrate Paleontology (SVP) was founded in the US in 1940 for people with an interest in vertebrate paleontology; by 2014 it had about 2,000 members internationally, and holds annual meetings, mostly but not all in North America. It states exclusively educational and scientific purposes, with the objective to "advance the science of vertebrate paleontology and to serve the common interests and facilitate the cooperation of all persons concerned with the history, evolution, comparative anatomy, and taxonomy of vertebrate animals, as well as field occurrence, collection, and study of fossil vertebrates and the stratigraphy of the beds in which they are found." SVP is also concerned with the conservation and preservation of fossil sites. SVP publications include The Journal of Vertebrate Paleontology, The SVP Memoir Series, The News Bulletin, The Bibliography of Fossil Vertebrates and most recently Palaeontologia Electronica.

text: The Society of Vertebrate Paleontology (SVP) was founded in the US in 1940 for people with an interest in

text: vertebrate paleontology

text: ; by 2014 it had about 2,000 members internationally, and holds annual meetings, mostly but not all in North America. It states exclusively educational and scientific purposes, with the objective to "advance the

text: science

text: of vertebrate paleontology and to serve the common interests and facilitate the cooperation of all persons concerned with the history,

text: evolution

text: comparative anatomy

text: , and

text: taxonomy

text: of vertebrate animals, as well as field occurrence, collection, and study of fossil vertebrates and the

text: stratigraphy

text: of the beds in which they are found." SVP is also concerned with the conservation and preservation of fossil sites. SVP publications include The

text: Journal of Vertebrate Paleontology

text: , The SVP Memoir Series, The News Bulletin, The

text: Bibliography of Fossil Vertebrates

text: and most recently

text: Palaeontologia Electronica

text: A vertebral fixation procedure may be indicated in cases of vertebral fracture, vertebral deformity, or degenerative vertebral disorders (such as spondylolisthesis).

text: A vertebral fixation procedure may be indicated in cases of

text: vertebral fracture

text: vertebral deformity

text: , or degenerative vertebral disorders (such as

text: spondylolisthesis

text: The history of biodiversity during the Phanerozoic (the last 540 million years), starts with rapid growth during the Cambrian explosion—a period during which nearly every phylum of multicellular organisms first appeared. Over the next 400 million years or so, invertebrate diversity showed little overall trend and vertebrate diversity shows an overall exponential trend. This dramatic rise in diversity was marked by periodic, massive losses of diversity classified as mass extinction events. A significant loss occurred when rainforests collapsed in the carboniferous. The worst was the Permian-Triassic extinction event, 251 million years ago. Vertebrates took 30 million years to recover from this event.

text: The history of biodiversity during the

text: Phanerozoic

text: (the last 540 million years), starts with rapid growth during the

text: Cambrian explosion

text: —a period during which nearly every

text: phylum

text: of

text: multicellular organism

text: s first appeared. Over the next 400 million years or so, invertebrate diversity showed little overall trend and vertebrate diversity shows an overall exponential trend. This dramatic rise in diversity was marked by periodic, massive losses of diversity classified as

text: mass extinction

text: events. A significant loss occurred when rainforests collapsed in the carboniferous. The worst was the

text: Permian-Triassic extinction event

text: , 251 million years ago. Vertebrates took 30 million years to recover from this event.

text: The anatomy of fish is often shaped by the physical characteristics of water, the medium in which fish live. Water is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does. The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always externally visible. The skeleton, which forms the support structure inside the fish, is either made of cartilage, in cartilaginous fish, or bone in bony fish. The main skeletal element is the vertebral column, composed of articulating vertebrae which are lightweight yet strong. The ribs attach to the spine and there are no limbs or limb girdles. The main external features of the fish, the fins, are composed of either bony or soft spines called rays which, with the exception of the caudal fins, have no direct connection with the spine. They are supported by the muscles which compose the main part of the trunk. The heart has two chambers and pumps the blood through the respiratory surfaces of the gills and on round the body in a single circulatory loop. The eyes are adapted for seeing underwater and have only local vision. There is an inner ear but no external or middle ear. Low frequency vibrations are detected by the lateral line system of sense organs that run along the length of the sides of fish, and these respond to nearby movements and to changes in water pressure.

text: The anatomy of fish is often shaped by the physical characteristics of

text: water

text: , the medium in which fish live. Water is much

text: denser

text: than

text: air

text: , holds a relatively small amount of dissolved

text: oxygen

text: , and absorbs more light than air does. The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always externally visible. The skeleton, which forms the support structure inside the fish, is either made of cartilage, in

text: cartilaginous fish

text: , or bone in

text: bony fish

text: vertebra

text: limbs

text: fins

text: , are composed of either bony or soft spines called rays which, with the exception of the

text: caudal fin

text: gill

text: middle ear

text: lateral line

text: Congenital vertebral anomalies are a collection of malformations of the spine.  Most around 85% are not clinically significant, but they can cause compression of the spinal cord by deforming the vertebral canal or causing instability.  This condition occurs in the womb. Congenital vertebral anomalies include alterations of the shape and number of  vertebrae.

text: Congenital vertebral anomalies are a collection of malformations of the

text: spine

text: .  Most around 85% are not clinically significant, but they can cause compression of the

text: spinal cord

text: by deforming the vertebral canal or causing instability.  This condition occurs in the womb. Congenital vertebral anomalies include alterations of the shape and number of

text: vertebra

text: e.

text: Some recent behavioral studies do not support the traditional view of sauropsid behavior as stereotyped and ritualistic (as in MacLean's reptilian complex). Birds have been shown to possess highly sophisticated cognitive abilities, such as the toolmaking of the New Caledonian crow and the language-like categorization abilities of the African grey parrot. Structures of the limbic system, which MacLean proposed arose in early mammals, have now been shown to exist across a range of modern vertebrates. The "paleomammalian" trait of parental care of offspring is widespread in birds and occurs in some fishes as well.  Thus, like the basal ganglia, the evolution of these systems presumably dates to a common vertebrate ancestor.

text: Some recent behavioral studies do not support the traditional view of sauropsid behavior as stereotyped and ritualistic (as in MacLean's reptilian complex). Birds have been shown to possess highly sophisticated cognitive abilities, such as the toolmaking of the

text: New Caledonian crow

text: and the language-like categorization abilities of the

text: African grey parrot

text: . Structures of the limbic system, which MacLean proposed arose in early mammals, have now been shown to exist across a range of modern vertebrates. The "paleomammalian" trait of parental care of offspring is widespread in birds and occurs in some fishes as well.  Thus, like the basal ganglia, the evolution of these systems presumably dates to a common vertebrate ancestor.

text: All of the SoxC proteins share 67% identity and 94% similarity in the 33 residues of the C-terminal domain.  All SoxC genes show 84% identity and 95% similarity to one another in the HMG box, which is just slightly more highly conserved than the C-terminal domain. The SoxC proteins only have between 45% to 67% identity to Sry and the other Sox proteins. The SoxC genes found in the Drosophila melanogaster (fly), Caenorhabditis elegans (worm), and other lower animals are closely linked to those found in humans and other vertebrates. The SoxC genes are highly conserved through vertebrate evolution and are similar enough to those in invertebrates and other lower animal species to speculate that these are based off an evolutionary necessity from before vertebrates and invertebrates separated through evolution.

text: All of the SoxC proteins share 67% identity and 94% similarity in the 33 residues of the C-terminal domain.  All SoxC genes show 84% identity and 95% similarity to one another in the HMG box, which is just slightly more highly conserved than the C-terminal domain. The SoxC proteins only have between 45% to 67% identity to Sry and the other Sox proteins. The SoxC genes found in the Drosophila melanogaster (fly), Caenorhabditis elegans (worm), and other lower animals are closely linked to those found in humans and other vertebrates. The SoxC genes are highly

text: conserved

text: through vertebrate evolution and are similar enough to those in invertebrates and other lower animal species to speculate that these are based off an evolutionary necessity from before vertebrates and invertebrates separated through evolution.

text: Quinto expressed interest in the role because of the duality of Spock's half-human, half-Vulcan heritage, and how the character "is constantly exploring that notion of how to evolve in a responsible way and how to evolve in a respectful way. I think those are all things that we as a society, and certainly the world, could implement." The Pittsburgh Post-Gazette interview was circulated, and attracted the attention of director J.J. Abrams. Quinto was subsequently the first actor to be cast in the film, while Nimoy was confirmed to return as the older "Prime" version of Spock from the main timeline.

text: Quinto expressed interest in the role because of the duality of Spock's half-human, half-Vulcan heritage, and how the character "is constantly exploring that notion of how to evolve in a responsible way and how to evolve in a respectful way. I think those are all things that we as a society, and certainly the world, could implement." The Pittsburgh Post-Gazette interview was circulated, and attracted the attention of director

text: J.J. Abrams

text: . Quinto was subsequently the first actor to be cast in the film, while Nimoy was confirmed to return as the older "Prime" version of Spock from the main timeline.

text: The sclerotome forms the vertebrae and the rib cartilage and part of the occipital bone; the myotome forms the musculature of the back, the ribs and the limbs; the syndetome forms the tendons and the dermatome forms the skin on the back. In addition, the somites specify the migration paths of neural crest cells and the axons of spinal nerves. From their initial location within the somite, the sclerotome cells migrate medially towards the notochord. These cells meet the sclerotome cells from the other side to form the vertebral body. The lower half of one sclerotome fuses with the upper half of the adjacent one to form each vertebral body. From this vertebral body, sclerotome cells move dorsally and surround the developing spinal cord, forming the vertebral arch. Other cells move distally to the costal processes of thoracic vertebrae to form the ribs.

text: The sclerotome forms the

text: vertebra

text: e and the rib cartilage and part of the occipital bone; the myotome forms the

text: musculature

text: of the back, the ribs and the limbs; the syndetome forms the tendons and the dermatome forms the

text: skin

text: on the back. In addition, the somites specify the migration paths of

text: neural crest

text: cells and the

text: axon

text: s of

text: spinal nerve

text: s. From their initial location within the somite, the sclerotome cells migrate medially towards the

text: notochord

text: . These cells meet the sclerotome cells from the other side to form the vertebral body. The lower half of one sclerotome fuses with the upper half of the adjacent one to form each vertebral body. From this vertebral body, sclerotome cells move dorsally and surround the developing

text: spinal cord

text: , forming the

text: vertebral arch

text: thoracic vertebrae

text: to form the ribs.

text: During the Early Jurassic period, the land that is now the Kayenta Formation experienced rainy summers and dry winters.  By the Middle Jurassic period it was being encroached upon from the north by a sandy dune field that would become the Navajo Sandstone. The animals here were adapted to a seasonal climate and abundant water could be found in streams, ponds and lakes. C. kayentakatae shared its paleoenvironment with other dinosaurs, such as several theropods including Dilophosaurus, Kayentavenator, the "Shake N Bake" theropod, the basal sauropodomorph Sarahsaurus,heterodontosaurids, and the armored dinosaurs Scelidosaurus and Scutellosaurus. The Kayenta Formation has produced that remains of three coelophysoid taxa of different body size, which represents the most diverse ceratosaur fauna yet known. The Kayenta Formation has yielded a small but growing assemblage of organisms. Vertebrates present in the Kayenta Formation at the time of C.kayentakatae included hybodont sharks, bony fish known as osteichthyes, lungfish, salamanders, the frog Prosalirus, the caecilian Eocaecilia, the turtle Kayentachelys, a sphenodontian reptile, various lizards.  Also present were the synapsids Dinnebiton, Kayentatherium, and Oligokyphus., several early crocodylomorphs including Calsoyasuchus, Eopneumatosuchus, Kayentasuchus, and Protosuchus, and the pterosaur Rhamphinion. The possible presence of the early true mammal Dinnetherium, and a haramyid mammal has also been proposed, based on fossil finds. Vertebrate trace fossils from this area included coprolites and the tracks of therapsids, lizard-like animals, and dinosaurs, which provided evidence that these animals were also present. Non-vertebrates in this ecosystem included microbial or "algal" limestone, freshwater bivalves, freshwater mussels and snails, and ostracods. The plant life known from this area included trees that became preserved as petrified wood.

text: During the Early Jurassic period, the land that is now the Kayenta Formation experienced rainy summers and dry winters.  By the Middle Jurassic period it was being encroached upon from the north by a sandy dune field that would become the

text: Navajo Sandstone

text: . The animals here were adapted to a seasonal climate and abundant water could be found in streams, ponds and lakes. C. kayentakatae shared its

text: paleoenvironment

text: Kayentavenator

text: , the "Shake N Bake" theropod, the

text: basal

text: sauropodomorph

text: Sarahsaurus

text: heterodontosaurids

text: , and the armored dinosaurs

text: Scelidosaurus

text: and

text: Scutellosaurus

text: . The Kayenta Formation has produced that remains of three coelophysoid taxa of different body size, which represents the most diverse ceratosaur fauna yet known. The Kayenta Formation has yielded a small but growing assemblage of organisms. Vertebrates present in the Kayenta Formation at the time of C.kayentakatae included

text: hybodont

text: sharks,

text: bony fish

text: known as osteichthyes,

text: lungfish

text: , salamanders, the frog

text: Prosalirus

text: , the

text: caecilia

text: n

text: Eocaecilia

text: , the turtle

text: Kayentachelys

text: , a

text: sphenodontia

text: synapsids

text: Dinnebiton,

text: Kayentatherium

text: , and

text: Oligokyphus

text: ., several early

text: crocodylomorphs

text: including

text: Calsoyasuchus

text: Eopneumatosuchus

text: Kayentasuchus

text: , and

text: Protosuchus

text: , and the

text: pterosaur

text: Rhamphinion

text: . The possible presence of the early true mammal

text: Dinnetherium

text: , and a

text: haramyid

text: mammal has also been proposed, based on fossil finds. Vertebrate trace fossils from this area included

text: coprolite

text: s and the tracks of

text: therapsid

text: ostracod

text: MafK was first cloned and identified in chicken in 1993 as a member of the small Maf (sMaf) genes. MafK was also identified as p18 NF-E2, a component of NF-E2 complex binding to a specific motif (NF-E2) in the regulatory regions of β-globin and other erythroid-related genes. MAFK has been identified in many vertebrates, including humans. There are three functionally redundant sMaf proteins in vertebrates, MafF, MafG, and MafK.

text: Fish may have evolved from a creature similar to a coral-like Sea squirt, whose larvae resemble primitive fish in important ways. The first ancestors of fish may have kept the larval form into adulthood (as some sea squirts do today), although perhaps the reverse is the case.

text: Fish may have evolved from a creature similar to a coral-like

text: Sea squirt

text: , whose larvae resemble primitive fish in important ways. The first ancestors of fish may have

text: kept the larval form into adulthood

text: Studies on Palaeophis vertebrae show a high degree of vascularisation, suggesting that it had a considerably faster metabolism and growth rate than modern snakes. This may suggest that palaeophiids, like other marine reptiles such as mosasaurs, might had developed towards endothermy.

text: Studies on Palaeophis vertebrae show a high degree of vascularisation, suggesting that it had a considerably faster metabolism and growth rate than modern snakes. This may suggest that palaeophiids, like other marine reptiles such as

text: mosasaur

text: s, might had developed towards endothermy.

text: Like all Plasmodium species P. fischeri has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. fischeri has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: It is both biochemically and medically interesting how tarantula hawk venom works. How can an essentially non-toxic venom that causes so much pain, described as blinding, debilitating, and shockingly electric by Schmidt, subside in only three minutes in humans? Only the bullet ant is ranked higher than the tarantula hawk’s sting on Schmidt’s Sting Pain Index. How does it permanently paralyze a tarantula, yet keep it alive? It is also evolutionarily interesting and significant how such a toxin evolved. Selection pressure by potential vertebrate predators would have favored individuals with painful venom components, but not vertebrate-lethal components. At the same time, selection pressure against venom lethality towards prey and subsequent loss of prey to spoilage would be very strong. The tarantula hawk’s venom is a specific, evolutionarily tailored cocktail of compounds best suited to the wasps’ needs. Studying tarantula hawk venom may help us gain insight into treating human problems like chronic pain from injury or disease.

text: It is both biochemically and medically interesting how tarantula hawk

text: venom

text: works. How can an essentially non-toxic venom that causes so much pain, described as blinding, debilitating, and shockingly electric by Schmidt, subside in only three minutes in humans? Only the bullet ant is ranked higher than the tarantula hawk’s sting on Schmidt’s Sting Pain Index. How does it permanently paralyze a tarantula, yet keep it alive? It is also evolutionarily interesting and significant how such a toxin evolved. Selection pressure by potential vertebrate predators would have favored individuals with painful venom components, but not vertebrate-lethal components. At the same time, selection pressure against venom lethality towards prey and subsequent loss of prey to spoilage would be very strong. The tarantula hawk’s venom is a specific, evolutionarily tailored cocktail of compounds best suited to the wasps’ needs. Studying tarantula hawk venom may help us gain insight into treating human problems like chronic pain from injury or disease.

text: The goal of comparative embryology is to make sense of how an embryo develops, and of how all animals are related. Comparative embryology also supports evolutionary theory, in the sense that all vertebrates develop similarly. The conclusion is that all vertebrates must have a common ancestor.

text: The vertebrates traditionally include the hagfish, which do not have proper vertebrae, though their closest living relatives, the lampreys, do. Hagfish do, however, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as "Craniata" when discussing morphology.

text: The vertebrates traditionally include the

text: hagfish

text: , which do not have proper

text: vertebrae

text: , though their closest living relatives, the

text: lamprey

text: s, do. Hagfish do, however, possess a

text: cranium

text: Craniata

text: " when discussing morphology.

text: The trabecular cartilages were first described in the grass snake by Martin Heinrich Rathke at 1839.In 1874, Thomas Henry Huxley pointed out that the trabecular cartilages are the modified viscerocranium: they assumed as the serial homologues of the branchial skeletons in the pharyngeal arches.The vertebrate jaw is generally thought to be the modification of the mandibular arch (1st pharyngeal arch). Since the trabecular cartilages appear anterior to the mandibular arch, if the trabecular cartilages are serial homologues of the pharyngeal arches, the ancestral vertebrates should possess more than one pharyngeal arch (so called “premandibular arches”) anterior to the mandibular arch.The existence of premandibular arch(es) has been accepted by many comparative embryologists and morphologists (e. g., Edwin Stephen Goodrich, Gavin de Beer). Moreover, Erik Stensio reported premandibular arches and the corresponding branchiomeric nerves by the reconstruction of the Osteostracans (e.g., Cephalaspis; recently this arch was reinterpreted as the mandibular arch)However, the existence of the premandibular arch(es) is rejected today, and the trabecular cartilages are not assumed to be one of the pharyngeal arches any more.

text: The trabecular cartilages were first described in the

text: grass snake

text: by

text: Martin Heinrich Rathke

text: at 1839.In 1874,

text: Thomas Henry Huxley

text: pointed out that the trabecular cartilages are the modified

text: viscerocranium

text: : they assumed as the serial homologues of the branchial skeletons in the

text: pharyngeal arches

text: .The vertebrate

text: jaw

text: is generally thought to be the modification of the

text: mandibular arch

text: (1st pharyngeal arch). Since the trabecular cartilages appear anterior to the mandibular arch, if the trabecular cartilages are serial homologues of the pharyngeal arches, the ancestral vertebrates should possess more than one pharyngeal arch (so called “premandibular arches”) anterior to the mandibular arch.The existence of premandibular arch(es) has been accepted by many comparative embryologists and morphologists (e. g.,

text: Edwin Stephen Goodrich

text: Gavin de Beer

text: ). Moreover,

text: Erik Stensio

text: reported premandibular arches and the corresponding branchiomeric nerves by the reconstruction of the

text: Osteostracans

text: (e.g.,

text: Cephalaspis

text: ; recently this arch was reinterpreted as the mandibular arch)However, the existence of the premandibular arch(es) is rejected today, and the trabecular cartilages are not assumed to be one of the pharyngeal arches any more.

text: The immunoglobulin new antigen receptor (IgNAR) of cartilaginous fishes (for example sharks) is a heavy-chain antibody. IgNAR shows significant structural differences to other antibodies. It has five constant domains (C) per chain instead of the usual three, several disulfide bonds in unusual positions, and the complementarity determining region 3 (CDR3) forms an extended loop covering the site which binds to a light chain in other antibodies. These differences, in combination with the phylogenetic age of the cartilaginous fishes, have led to the hypothesis that IgNAR could be more closely related to a primordial antigen-binding protein than the mammalian immunoglobulins. To test this hypothesis, it would be necessary to discover IgNAR or similar antibodies in vertebrates that are phylogenetically still older, like the jawless fish lamprey and hagfish. Non-vertebrates do not have antibodies at all.

text: The immunoglobulin new antigen receptor (IgNAR) of

text: cartilaginous fish

text: es (for example sharks) is a heavy-chain antibody. IgNAR shows significant structural differences to other antibodies. It has five constant domains (C) per chain instead of the usual three, several

text: disulfide bond

text: s in unusual positions, and the

text: complementarity determining region

text: 3 (CDR3) forms an extended loop covering the site which binds to a light chain in other antibodies. These differences, in combination with the

text: phylogenetic

text: age of the cartilaginous fishes, have led to the hypothesis that IgNAR could be more closely related to a primordial antigen-binding protein than the

text: mammal

text: ian immunoglobulins. To test this hypothesis, it would be necessary to discover IgNAR or similar antibodies in

text: vertebrate

text: s that are phylogenetically still older, like the

text: jawless fish

text: lamprey

text: and

text: hagfish

text: Non-vertebrate

text: s do not have antibodies at all.

text: The shared trait of breathing via gills in bony fish and cartilaginous fish is a famous example of symplesiomorphy. Bony fish are more closely related to terrestrial vertebrates, which evolved out of a clade of bony fishes that breathe through their skin or lungs, than they are to the sharks, rays, and the other cartilaginous fish. Their kind of gill respiration is shared by the "fishes" because it was present in their common ancestor and lost in the other living vertebrates. But based on this shared trait, we cannot infer that bony fish are more closely related to sharks and rays than they are to terrestrial vertebrates.

text: The shared trait of breathing via gills in bony fish and cartilaginous fish is a famous example of

text: symplesiomorphy

text: . Bony fish are more closely related to

text: terrestrial vertebrates

text: , which evolved out of a clade of bony fishes that breathe through their skin or lungs, than they are to the sharks, rays, and the other cartilaginous fish. Their kind of gill respiration is shared by the "fishes" because it was present in their common ancestor and lost in the other living vertebrates. But based on this shared trait, we cannot infer that bony fish are more closely related to sharks and rays than they are to terrestrial vertebrates.

text: The vertebral structure in C. aguti is that commonly possessed by primitive reptiles. The centra are amphicoelous and notochordal, with swollen, relatively massive neural arches. The vertebral column is differentiated into presacral, sacral, and postsacral or caudal vertebrae.

text: The vertebral structure in C. aguti is that commonly possessed by primitive reptiles. The centra are

text: amphicoelous

text: and notochordal, with swollen, relatively massive

text: neural arches

text: . The

text: vertebral column

text: is differentiated into presacral, sacral, and postsacral or caudal vertebrae.

text: Like all Plasmodium species P. telfordi has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. telfordi has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: The dracula fish is unusual in that its ancestors lost their true teeth around 50 million years ago, but re-evolved its bone fangs as a replacement around 30 million years ago. The species is sexually dimorphic in that the female does not have such prominent bone fangs. It becomes sexually mature while its body is still not fully developed; scientists speculate that this may happen because younger fish were more successful reproductively. Ichthyologist Dr Ralf Britz, who named the fish after Bram Stoker's character Count Dracula, stated that the dracula fish "is one of the most extraordinary vertebrates discovered in the last few decades."

text: The dracula fish is unusual in that its ancestors lost their true teeth around 50 million years ago, but re-evolved its bone fangs as a replacement around 30 million years ago. The species is

text: sexually dimorphic

text: in that the female does not have such prominent bone fangs. It becomes sexually mature while its body is still not fully developed; scientists speculate that this may happen because younger fish were more successful reproductively.

text: Ichthyologist

text: Dr Ralf Britz, who named the fish after

text: Bram Stoker

text: 's character

text: Count Dracula

text: , stated that the dracula fish "is one of the most extraordinary

text: vertebrates

text: discovered in the last few decades."

text: Like all Plasmodium species P. tropiduri has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. tropiduri has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: Most freshwater mussels reproduce by releasing their larvae, called glochidia, into the water, where they are then taken in by fish. The glochidia lodge in the gills or fins of the fish and develop into juvenile mussels encysted in the fish tissue. They then drop off the fish into the substrate. Little is known about how this species transfers its glochidia to fish hosts, but it may occur when the adult female is eaten by the fish. The fish host for this mussel species is the freshwater drum (Aplodinotus grunniens).

text: Most freshwater mussels reproduce by releasing their larvae, called

text: glochidia

text: , into the water, where they are then taken in by fish. The glochidia lodge in the gills or fins of the fish and develop into juvenile mussels encysted in the fish tissue. They then drop off the fish into the substrate. Little is known about how this species transfers its glochidia to fish hosts, but it may occur when the adult female is eaten by the fish. The fish host for this mussel species is the

text: freshwater drum

text: (Aplodinotus grunniens).

text: Adaptation occurs through the gradual modification of existing structures. Consequently, structures with similar internal organisation may have different functions in related organisms. This is the result of a single ancestral structure being adapted to function in different ways. The bones within bat wings, for example, are very similar to those in mice feet and primate hands, due to the descent of all these structures from a common mammalian ancestor. However, since all living organisms are related to some extent, even organs that appear to have little or no structural similarity, such as arthropod, squid and vertebrate eyes, or the limbs and wings of arthropods and vertebrates, can depend on a common set of homologous genes that control their assembly and function; this is called deep homology.

text: Adaptation occurs through the gradual modification of existing structures. Consequently, structures with similar internal organisation may have different functions in related organisms. This is the result of a single

text: ancestral structure

text: being adapted to function in different ways. The bones within

text: bat

text: wings, for example, are very similar to those in

text: mice

text: feet and

text: primate

text: hands, due to the descent of all these structures from a common mammalian ancestor. However, since all living organisms are related to some extent, even organs that appear to have little or no structural similarity, such as

text: arthropod

text: , squid and vertebrate eyes, or the limbs and wings of arthropods and vertebrates, can depend on a common set of homologous genes that control their assembly and function; this is called

text: deep homology

text: All Plasmodia are parasitic and require both a vertebrate host and an insect host to reproduce. Known vertebrate hosts include various primates (including humans), birds, rodents, bats, porcupines and squirrels. Mosquitoes of the genera Culex, Anopheles, Culiseta, Mansonia and Aedes often serve as insect hosts for various Plasmodium species.

text: All Plasmodia are parasitic and require both a vertebrate host and an insect host to reproduce. Known vertebrate hosts include various

text: primates

text: (including humans), birds, rodents,

text: bat

text: s,

text: porcupine

text: s and

text: squirrel

text: s. Mosquitoes of the genera

text: Culex

text: Anopheles

text: Culiseta

text: Mansonia

text: and

text: Aedes

text: often serve as insect hosts for various Plasmodium species.

text: The vertebral column is the center of expression.  The driving impulse, however stems from the loins.  Every live impulse begins in this region, even if it is invisible from the outside.

text: The

text: vertebral column

text: is the center of expression.  The driving impulse, however stems from the

text: loins

text: .  Every live impulse begins in this region, even if it is invisible from the outside.

text: In 1977, Schmidtke and colleagues showed that isozyme complexity is similar in amphioxus and tunicates, contradicting a prediction of Ohno's hypothesis that genome duplication occurred in the common ancestor of amphioxus and vertebrates. However, this analysis did not examine vertebrates, so could say nothing about later duplication events. (Furthermore, much later molecular phylogenetics has shown that vertebrates are more closely related to tunicates than to amphioxus, thus negating the logic of this analysis.) The 2R hypothesis saw a resurgence of interest in the 1990s for two reasons. First, gene mapping data in humans and mice revealed extensive paralogy regions - sets of genes on one chromosome related to sets of genes on another chromosome in the same species, indicative of duplication events in evolution. Paralogy regions were generally in sets of four. Second, cloning of Hox genes in amphioxus revealed presence of a single Hox gene cluster, in contrast to the four clusters in humans and mice. Data from additional gene families revealed a common one-to-many rule when amphioxus and vertebrate genes were compared. Taken together, these two lines of evidence suggest that two genome duplications occurred in the ancestry of vertebrates, after it had diverged from the cephalochordate evolutionary lineage.

text: In 1977, Schmidtke and colleagues showed that

text: isozyme

text: complexity is similar in

text: amphioxus

text: and

text: tunicates

text: , contradicting a prediction of Ohno's hypothesis that

text: genome duplication

text: occurred in the common ancestor of

text: amphioxus

text: and

text: vertebrates

text: . However, this analysis did not examine

text: vertebrates

text: , so could say nothing about later duplication events. (Furthermore, much later

text: molecular phylogenetics

text: has shown that

text: vertebrates

text: are more closely related to

text: tunicates

text: than to

text: amphioxus

text: , thus negating the logic of this analysis.) The 2R hypothesis saw a resurgence of interest in the 1990s for two reasons. First, gene mapping data in humans and mice revealed extensive

text: paralogy regions

text: - sets of genes on one chromosome related to sets of genes on another chromosome in the same species, indicative of duplication events in evolution. Paralogy regions were generally in sets of four. Second, cloning of

text: Hox gene

text: s in

text: amphioxus

text: revealed presence of a single

text: Hox gene cluster

text: , in contrast to the four clusters in humans and mice. Data from additional

text: gene families

text: revealed a common one-to-many rule when

text: amphioxus

text: and

text: vertebrate

text: genes were compared. Taken together, these two lines of evidence suggest that two genome duplications occurred in the ancestry of

text: vertebrates

text: , after it had diverged from the

text: cephalochordate

text: evolutionary lineage.

text: The fossil vertebrate record of the Eocene Arctic includes giant tortoises, varanid lizards, and boid snakes. Mammal fossils are extremely diverse, including the rhino-like brontotheres, the hippo-like Coryphodon, a tapir like relative (Thuliadanta), an early horse (Hyracotherium?), carnivores (e.g., Viverravus, Miacis), meat-eating creodonts (e.g. Paaeonictis), a mesonychid (Pachyaena), a small swimming carnivore (Pantolestid), a leptictid and at least five rodents (including Paramys and Microparamys). There are over 40 fossil vertebrate sites in the Strathcona Fiord region.

text: The fossil vertebrate record of the Eocene Arctic includes giant tortoises,

text: varanid

text: lizards, and

text: boid

text: snakes. Mammal fossils are extremely diverse, including the rhino-like

text: brontotheres

text: , the hippo-like

text: Coryphodon

text: , a

text: tapir

text: like relative (Thuliadanta), an early horse (

text: Hyracotherium

text: ?), carnivores (e.g.,

text: Viverravus

text: Miacis

text: ), meat-eating

text: creodonts

text: (e.g. Paaeonictis), a

text: mesonychid

text: Pachyaena

text: ), a small swimming carnivore (

text: Pantolestid

text: ), a

text: leptictid

text: and at least five rodents (including

text: Paramys

text: and Microparamys). There are over 40 fossil vertebrate sites in the Strathcona Fiord region.

text: According to Sulej (2007), the intercentra of cervical and thoracic vertebra are fully ossified. The pleurocentra are not preserved and no evidence is found that they were present as cartilages. The atlas, axis, and third and fourth cervical vertebrae are characteristic and similar to those in stereospondyls. The morphology of atlas, axis, third and fourth vertebrae suggest that the neck of Metoposaurus was relatively flexible. The intercentra of the region where the vertebral column contacts the shoulder girdle are flat anteriorly and posteriorly. The neural arches have almost vertically set prezygapophyses (vide postcervical vertebrae).This suggests that in this region the lateral bending of the vertebral column was very limited. It was probably connected with articulation of the vertebral column with the shoulder girdle. A stiffening of the vertebral column, in the region of contacting limbs, was apparently essential for the swimming.He also describes that in Metoposaurus diagnosticus krasiejowensis, the parapophyses become shorter posteriorly, similarly to plagiosaurids.The intercentra of dorsal and sacral vertebrae are fully ossified and form quite short disks, not connected with the neural arches. In the dorsal and sacral region, they have anterior and posterior surfaces concave or the posterior surface is almost flat. This condition resembles that in the trunk of plesiosaurs and, to some degree, the ichthyosaurs, confirming the aquatic mode of life.

text: According to Sulej (2007), the intercentra of

text: cervical

text: and

text: thoracic

text: vertebra

text: are fully ossified. The pleurocentra are not preserved and no evidence is found that they were present as cartilages. The

text: atlas

text: axis

text: , and third and fourth

text: cervical

text: vertebrae

text: are characteristic and similar to those in stereospondyls. The morphology of atlas, axis, third and fourth vertebrae suggest that the neck of Metoposaurus was relatively flexible. The intercentra of the region where the vertebral column contacts the shoulder girdle are flat anteriorly and posteriorly. The neural arches have almost vertically set prezygapophyses (vide postcervical vertebrae).This suggests that in this region the lateral bending of the vertebral column was very limited. It was probably connected with articulation of the vertebral column with the shoulder girdle. A stiffening of the vertebral column, in the region of contacting limbs, was apparently essential for the swimming.He also describes that in Metoposaurus diagnosticus krasiejowensis, the parapophyses become shorter posteriorly, similarly to plagiosaurids.The intercentra of dorsal and sacral vertebrae are fully ossified and form quite short disks, not connected with the neural arches. In the dorsal and sacral region, they have anterior and posterior surfaces concave or the posterior surface is almost flat. This condition resembles that in the trunk of plesiosaurs and, to some degree, the ichthyosaurs, confirming the aquatic mode of life.

text: The trabecular cartilages generally appear as a paired, rod-shaped cartilages at the ventral side of the forebrain and lateral side of the adenohypophysis in the vertebrate embryo. During development, their anterior ends fuse and form the trabecula communis. Their posterior ends fuse with parachordal cartilages.

text: The trabecular cartilages generally appear as a paired, rod-shaped cartilages at the ventral side of the

text: forebrain

text: and lateral side of the

text: adenohypophysis

text: in the vertebrate embryo. During development, their anterior ends fuse and form the trabecula communis. Their posterior ends fuse with

text: parachordal cartilages

text: A third specimen of Sclerothorax was discovered in 1967 that preserved the vertebral column and the lower jaw. It was described in 2004 by Michael Fastnacht, who also reported that the specimen had an impression of the palate. The palate seemed to be long and narrow like that of another German temnospondyl called Trematosaurus. Fastnacht therefore concluded that Huene's two specimens belonged to different species, with the first high-spined specimen referable to Sclerothorax. However, three more specimens were uncovered in German museum collections with nearly complete skulls attached to vertebral columns. These specimens had broad heads, proving that Huene's second specimen also belongs to Sclerothorax.

text: A third specimen of Sclerothorax was discovered in 1967 that preserved the vertebral column and the lower jaw. It was described in 2004 by Michael Fastnacht, who also reported that the specimen had an impression of the

text: palate

text: . The palate seemed to be long and narrow like that of another German temnospondyl called

text: Trematosaurus

text: . Fastnacht therefore concluded that Huene's two specimens belonged to different species, with the first high-spined specimen referable to Sclerothorax. However, three more specimens were uncovered in German museum collections with nearly complete skulls attached to vertebral columns. These specimens had broad heads, proving that Huene's second specimen also belongs to Sclerothorax.

text: Meckel's cartilage is a piece of cartilage from which the mandibles (lower jaws) of vertebrates evolved. Originally it was the lower of two cartilages which supported the first gill arch (nearest the front) in early fish. Then it grew longer and stronger, and acquired muscles capable of closing the developing jaw. In early fish and in chondrichthyans (cartilaginous fish such as sharks), Meckel's cartilage continued to be the main component of the lower jaw. But in the adult forms of osteichthyans (bony fish) and their descendants (amphibians, reptiles, birds and mammals) the cartilage was covered in bone - although in their embryos the jaw initially develops as the Meckel's cartilage. In tetrapods the cartilage partially ossifies (changes to bone) at the rear end of the jaw and becomes the articular bone, which forms part of the jaw joint in all tetrapods except mammals.

text: Meckel's cartilage

text: is a piece of

text: cartilage

text: vertebrates

text: evolved. Originally it was the lower of two cartilages which supported the first gill arch (nearest the front) in early fish. Then it grew longer and stronger, and acquired muscles capable of closing the developing jaw. In early fish and in

text: chondrichthyans

text: (cartilaginous fish such as

text: shark

text: s), Meckel's cartilage continued to be the main component of the lower jaw. But in the adult forms of

text: osteichthyans

text: (bony fish) and their descendants (amphibians, reptiles, birds and mammals) the cartilage was covered in bone - although in their

text: embryos

text: the jaw initially develops as the Meckel's cartilage. In

text: tetrapods

text: the cartilage partially

text: ossifies

text: (changes to bone) at the rear end of the jaw and becomes the

text: articular

text: mammals

text: Osteochondromas are benign lesions and do not affect life expectancy. Complete excision of osteochondroma is curative and the reoccurrences take place when the removal of tumor is incomplete. Multiple reoccurrences in a well-excised lesion indicate that it may be malignant. The risk of malignant transformation takes place in 1–5% of individuals. If any symptoms of cancerous tumor takes place, then the patient should be evaluated by a bone specialist. No treatment is necessary for Solitary osteochondromas that are asymptomatic. Treatments for solitary osteochondroma are careful observation over time and taking regular x-rays to monitor any changes in the tumor. If the lesion is causing pain with activity, nerve or vessel impingement, or if the bone growth has fully matured and the presence of a large cartilage cap is prominent, then it is advised that the tumor be surgically removed.

text: The Dry Mesa Dinosaur Quarry of western Colorado yields one of the most diverse Upper Jurassic vertebrate assemblages in the world. This fossil assemblage was deposited within a poorly sorted sandstone bed that is stratigraphically situated in the lower portion of the upper Brushy Basin Member of the Morrison Formation. The bone accumulation, consisting of thousands of bones, was the consequence of two cataclysmic events, a drought, and flash flood. In the Dry Mesa area, a severe drought resulted in the mass mortality of dinosaurs and other vertebrates. These animals were attracted to a remnant water hole of the dry Lake T'oo'dichi' lake bed where they died of starvation and dehydration. This mass mortality produced a considerable accumulation of disarticulated vertebrate remains.  Subsequently, a short-lived flash flood traversed the dry lake beds. The quarry sandstone bed is a 2 meter thick, 121 meter wide, very poorly sorted pebble-rich sublitharenite. The channel sandstone shows abundant trough cross-stratification and a possible antidune bedform composed of gravel and sand which indicates flow velocities as high as 200 cm/s (5 miles/hour). Measured bone volumes can be equated to flow velocities. These calculated bone volume velocities are in agreement with flow velocities determined from grain size and bedforms. The river flow direction, based upon bedform orientations and bone elongation statistics, was to the east-northeast. Geologic and taphonomic characteristics indicate a short transport distance for the bone accumulation (Richmond and Morris, 1999).

text: The Dry Mesa Dinosaur Quarry of western Colorado yields one of the most diverse Upper

text: Jurassic

text: vertebrate assemblages in the world. This fossil assemblage was deposited within a poorly sorted

text: sandstone

text: bed that is stratigraphically situated in the lower portion of the upper Brushy Basin Member of the

text: Morrison Formation

text: . The bone accumulation, consisting of thousands of bones, was the consequence of two cataclysmic events, a

text: drought

text: , and

text: flash flood

text: . In the Dry Mesa area, a severe drought resulted in the mass mortality of

text: dinosaur

text: s and other

text: vertebrates

text: . These animals were attracted to a remnant water hole of the dry Lake T'oo'dichi' lake bed where they died of starvation and dehydration. This mass mortality produced a considerable accumulation of disarticulated vertebrate remains.  Subsequently, a short-lived flash flood traversed the dry lake beds. The quarry sandstone bed is a 2 meter thick, 121 meter wide, very poorly sorted pebble-rich sublith

text: arenite

text: . The channel

text: sandstone

text: shows abundant trough cross-stratification and a possible

text: antidune

text: bedform composed of gravel and sand which indicates flow velocities as high as 200 cm/s (5 miles/hour). Measured bone volumes can be equated to flow

text: velocities

text: . These calculated bone volume velocities are in agreement with flow

text: velocities

text: determined from

text: grain size

text: and bedforms. The river flow direction, based upon bedform orientations and bone elongation statistics, was to the east-northeast.

text: Geologic

text: and

text: taphonomic

text: characteristics indicate a short transport distance for the bone accumulation (Richmond and Morris, 1999).

text: Mammalian endothermy and homeothermy are potent nonspecific defenses against most fungi.

text: Mammalian

text: endothermy

text: and homeothermy are potent nonspecific defenses against most fungi.

text: During the Cambrian, the first vertebrate animals, among them the first fishes, had appeared. A creature that could have been the ancestor of the fishes, or was probably closely related to it, was Pikaia. It had a primitive notochord, a structure that could have developed into a vertebral column later. The first fishes with jaws (Gnathostomata) appeared during the next geological period, the Ordovician. The colonisation of new niches resulted in massive body sizes. In this way, fishes with increasing sizes evolved during the early Paleozoic, such as the titanic placoderm Dunkleosteus, which could grow  long.

text: During the Cambrian, the first

text: vertebrate

text: animals, among them the first

text: fishes

text: , had appeared. A creature that could have been the ancestor of the fishes, or was probably closely related to it, was

text: Pikaia

text: . It had a primitive

text: notochord

text: vertebral column

text: later. The first fishes with

text: jaw

text: s (

text: Gnathostomata

text: ) appeared during the next geological period, the

text: Ordovician

text: . The colonisation of new

text: niche

text: s resulted in massive body sizes. In this way, fishes with increasing sizes evolved during the early Paleozoic, such as the titanic

text: placoderm

text: Dunkleosteus

text: , which could grow  long.

text: Every vertebra has a body, which consists of a large anterior middle portion called the centrum and a posterior vertebral arch, also called a neural arch. The body is composed of cancellous bone, which is the spongy type of osseous tissue,  whose micro-anatomy has been specifically studied within the pedicle bones. This cancellous bone is in turn, covered by a thin coating of cortical bone (or compact bone), the hard and dense type of osseous tissue. The vertebral arch and processes have thicker coverings of cortical bone. The upper and lower surfaces of the body of the vertebra are flattened and rough in order to give attachment to the intervertebral discs. These surfaces are the vertebral endplates which are in direct contact with the intervertebral discs and form the joint. The endplates are formed from a thickened layer of the cancellous bone of the vertebral body, the top layer being more dense. The endplates function to contain the adjacent discs, to evenly spread the applied loads, and to provide anchorage for the collagen fibers of the disc. They also act as a semi-permeable interface for the exchange of water and solutes.

text: Every vertebra has a body, which consists of a large anterior middle portion called the centrum and a posterior vertebral arch, also called a neural arch. The body is composed of

text: cancellous bone

text: , which is the spongy type of

text: osseous tissue

text: ,  whose micro-anatomy has been specifically studied within the pedicle bones. This cancellous bone is in turn, covered by a thin coating of

text: cortical bone

text: (or compact bone), the hard and dense type of osseous tissue. The vertebral arch and processes have thicker coverings of cortical bone. The upper and lower surfaces of the body of the vertebra are flattened and rough in order to give attachment to the

text: intervertebral discs

text: . These surfaces are the vertebral endplates which are in direct contact with the intervertebral discs and form the joint. The endplates are formed from a thickened layer of the cancellous bone of the vertebral body, the top layer being more dense. The endplates function to contain the adjacent discs, to evenly spread the applied loads, and to provide anchorage for the

text: collagen fibers

text: of the disc. They also act as a semi-permeable interface for the exchange of water and solutes.

text: Several structures that distinguish the vertebrates from other chordates are formed from the derivatives of neural crest cells.  In their "New head" theory, Gans and Northcut argue that the presence of neural crest was the basis for vertebrate specific features, such as sensory ganglia and cranial skeleton.  Furthermore, the appearance of these features was pivotal in vertebrate evolution because it enabled a predatory lifestyle.

text: It is still unclear what forces led to the development of a RAG1/2-mediated immune system exclusively in jawed vertebrates and not in any invertebrate species that also acquired the RAG1/2-containing transposon. Current hypotheses include two whole-genome duplication events in vertebrates, which would provide the genetic raw material for the development of the adaptive immune system, and the development of endothelial tissue, greater metabolic activity, and a decreased blood volume-to-body weight ratio, all of which are more specialized in vertebrates than invertebrates and facilitate adaptive immune responses.

text: Spontaneous vertebral artery dissection was described in the 1970s. Prior to this, there had been isolated case reports about carotid dissection. In 1971, C. Miller Fisher, a Canadian neurologist and stroke physician working at Massachusetts General Hospital, first noted the "string sign" abnormality in carotid arteries on cerebral angiograms of stroke patients, and subsequently discovered that the same abnormality could occur in the vertebral arteries. He reported the discovery in a paper in 1978.

text: Spontaneous vertebral artery dissection was described in the 1970s. Prior to this, there had been isolated case reports about carotid dissection. In 1971,

text: C. Miller Fisher

text: , a

text: Canadian

text: neurologist

text: and stroke physician working at

text: Massachusetts General Hospital

text: , first noted the "string sign" abnormality in carotid arteries on cerebral angiograms of stroke patients, and subsequently discovered that the same abnormality could occur in the vertebral arteries. He reported the discovery in a paper in 1978.

text: Plasmodium azurophilum is a species of the genus Plasmodium. Like all species in this genus it is a parasite of both vertebrates and insects. The vertebrate hosts are lizards of the genus Anolis.

text: Plasmodium azurophilum is a

text: species

text: of the

text: genus

text: Plasmodium

text: . Like all species in this genus it is a

text: parasite

text: of both

text: vertebrate

text: s and

text: insect

text: s. The vertebrate hosts are lizards of the genus

text: Anolis

text: Plateosaurus followed a trajectory similar to sauropods, but with a varied growth rate and final size as seen in extant reptiles, probably in response to environmental factors such as food availability. Some individuals were fully grown at only  total length, while others reached . However, the bone microstructure indicates rapid growth, as in sauropods and extant mammals, which suggests endothermy. Plateosaurus apparently represents an early stage in the development of endothermy, in which endothermy was decoupled from developmental plasticity. This hypothesis is based on a detailed study of Plateosaurus long-bone histology conducted by Martin Sander and Nicole Klein of the University of Bonn. A further indication for endothermy is the avian-style lung of Plateosaurus.

text: Plateosaurus followed a trajectory similar to sauropods, but with a varied growth rate and final size as seen in extant reptiles, probably in response to environmental factors such as food availability. Some individuals were fully grown at only  total length, while others reached . However, the bone microstructure indicates rapid growth, as in sauropods and extant mammals, which suggests

text: endothermy

text: . Plateosaurus apparently represents an early stage in the development of endothermy, in which endothermy was decoupled from developmental plasticity. This hypothesis is based on a detailed study of Plateosaurus long-bone histology conducted by Martin Sander and Nicole Klein of the University of Bonn. A further indication for endothermy is the avian-style lung of Plateosaurus.

text: Radiofrequency targeted vertebral augmentation (also written as RF-TVA) is a form of kyphoplasty that uses radiofrequency heat to control the viscosity of polymethylmethacrylate cement and deliver it into the vertebral body to treat vertebral compression fractures.

text: Radiofrequency targeted vertebral augmentation (also written as RF-TVA) is a form of

text: kyphoplasty

text: that uses radiofrequency heat to control the viscosity of

text: polymethylmethacrylate

text: cement and deliver it into the vertebral body to treat

text: vertebral compression fractures

text: Further studies on animals that were traditionally assumed to be cold-blooded have shown that most creatures incorporate different variations of the three terms defined above, along with their counterparts (ectothermy, poikilothermy, and bradymetabolism), thus creating a broad spectrum of body temperature types. Some fish have warm-blooded characteristics, such as the opah. Swordfish and some sharks have circulatory mechanisms that keep their brains and eyes above ambient temperatures, and thus increase their ability to detect and react to prey. Tunas and some sharks have similar mechanisms in their muscles, improving their stamina when swimming at high speed.

text: Further studies on animals that were traditionally assumed to be

text: cold-blooded

text: have shown that most creatures incorporate different variations of the three terms defined above, along with their counterparts (

text: ectothermy

text: poikilothermy

text: , and

text: bradymetabolism

text: ), thus creating a broad spectrum of body temperature types. Some

text: fish

text: have warm-blooded characteristics, such as the

text: opah

text: Swordfish

text: and some

text: shark

text: s have

text: circulatory

text: mechanisms that keep their

text: brain

text: s and

text: eye

text: s above ambient temperatures, and thus increase their ability to detect and react to

text: prey

text: . Tunas and some sharks have similar mechanisms in their muscles, improving their stamina when swimming at high speed.

text: The Majestic Picture Theatre, built in 1928 by one of Malanda's prominent settler families, the English family, is one of the oldest continually operating country picture theatres in Queensland. It contributes significantly to our understanding of how Queensland's leisure and entertainment history has evolved and is tangible evidence of this development in the tropical Far North. Before the introduction of television, picture theatres in Queensland enjoyed widespread popularity, particularly in rural areas providing not only entertainment but also a venue for social interaction. The Majestic Theatre is one of the few interwar picture theatres still screening regularly in Queensland.

text: Turkey has a large range of habitat types and the diversity of its fauna is very great. There are nearly 1,500 species of vertebrate recorded of which over 100 species, mostly fish, are endemic. The country is on two major routes used by migratory birds which swells the numbers in spring and autumn. The invertebrates are also very diverse, with about 19,000 species being recorded including 4,000 endemics.

text: Turkey has a large range of habitat types and the diversity of its

text: fauna

text: is very great. There are nearly 1,500 species of vertebrate recorded of which over 100 species, mostly fish, are endemic. The country is on two major routes used by

text: migratory

text: birds which swells the numbers in spring and autumn. The invertebrates are also very diverse, with about 19,000 species being recorded including 4,000 endemics.

text: The book grew out of the author's attempt to define what is meant by the life of vertebrates and by the evolution of that life. It combined an account of the embryology, anatomy, physiology, biochemistry, palaeontology, and ecology of all vertebrates and, the author argued, he has attempted via a documentation of the "central fact of biology, that life goes on", and to combine the results of the studies of these into a single work in which this continuity is maintained. It has been listed as the Book of A Lifetime by Colin Tudge who argues that the book might help humanity recover its humility and reverence in the face of nature rather than simply inspiring "awe".

text: The book grew out of the author's attempt to define what is meant by the life of vertebrates and by the evolution of that life. It combined an account of the embryology, anatomy, physiology, biochemistry, palaeontology, and ecology of all vertebrates and, the author argued, he has attempted via a documentation of the "central fact of biology, that life goes on", and to combine the results of the studies of these into a single work in which this continuity is maintained. It has been listed as the Book of A Lifetime by

text: Colin Tudge

text: who argues that the book might help humanity recover its humility and reverence in the face of nature rather than simply inspiring "awe".

text: The MTs from this diverse taxonomic range represent a high-heterogeneity sequence (regarding molecular weight and number and distribution of Cys residues) and do not show general homology; in spite of this, homology is found inside some taxonomic groups (such as vertebrate MTs).

text: The cervical vertebrae had well-developed cervical ribs, fused to the vertebral body. The ribs were elongated, with a forward-pointing process on the capitulum, the main rib head. The neural spines of the rear cervicals and front dorsals are transversely expanded at their upper ends due to rugosities serving as an attachment for tendons. This expanded sector projects to the front also, creating a notch on the lower front edge. Additionally the neural spine base is transversely constricted. Ridges extend to the rear from the sides of the neural spine base, over the upper sides of the rear joint processes, the postzygapophyses. These postzygapophyses themselves project far beyond the rear facet of the vertebral body, a derived trait. The prezygapophyses to the contrary, are much shorter; they have a notch at the front upper edge.

text: The cervical vertebrae had well-developed cervical ribs, fused to the vertebral body. The ribs were elongated, with a forward-pointing process on the capitulum, the main rib head. The neural spines of the rear cervicals and front dorsals are transversely expanded at their upper ends due to rugosities serving as an attachment for tendons. This expanded sector projects to the front also, creating a notch on the lower front edge. Additionally the neural spine base is transversely constricted. Ridges extend to the rear from the sides of the neural spine base, over the upper sides of the rear joint processes, the

text: postzygapophyses

text: . These postzygapophyses themselves project far beyond the rear facet of the vertebral body, a derived trait. The

text: prezygapophyses

text: to the contrary, are much shorter; they have a notch at the front upper edge.

text: Moreover, these clustered Pcdh genes are predominantly expressed in the developing nervous system and since different subsets of Pcdhs genes are differentially expressed in individual neurons, a vast cell surface diversity may arise from this combinatorial expression. This has led to speculation and further to the proposal that Pcdhs may provide a synaptic-address code for neuronal connectivity or a single-cell barcode for self-recognition/self-avoidance similar to that ascribed to DSCAM proteins of invertebrates. Although vertebrate DSCAMs lack the diversity of their invertebrate counterparts, the selective transcription of individual Pcdh isoforms can be achieved by promoter choice followed by alternative pre-mRNA cis-splicing thus increasing the number of possible combinations.

text: Moreover, these clustered Pcdh genes are predominantly expressed in the developing nervous system and since different subsets of Pcdhs genes are differentially expressed in individual neurons, a vast cell surface diversity may arise from this combinatorial expression. This has led to speculation and further to the proposal that Pcdhs may provide a synaptic-address code for neuronal connectivity or a single-cell barcode for self-recognition/self-avoidance similar to that ascribed to

text: DSCAM

text: proteins of invertebrates. Although vertebrate DSCAMs lack the diversity of their invertebrate counterparts, the selective transcription of individual Pcdh isoforms can be achieved by promoter choice followed by alternative pre-mRNA cis-splicing thus increasing the number of possible combinations.

text: With the patient placed under general or local anesthesia, the procedure is performed under C-arm imaging.  The correct (damaged) vertebrae are identified for the procedure.  Using a bone access needle the vertebra is drilled in order to make a channel through the vertebral arch pedicle.  This channel is used to deliver the PTFE bag within which the injected bone cement will reside.   Once the bag is introduced, acrylic bone cement is injected until the vertebrae is judged to be restored to its near original height.

text: With the patient placed under general or local

text: anesthesia

text: , the procedure is performed under C-arm imaging.  The correct (damaged) vertebrae are identified for the procedure.  Using a

text: bone access needle

text: the vertebra is drilled in order to make a channel through the

text: vertebral arch pedicle

text: .  This channel is used to deliver the

text: PTFE

text: bag within which the injected

text: bone cement

text: will reside.   Once the bag is introduced, acrylic bone cement is injected until the vertebrae is judged to be restored to its near original height.

text: The fact that alpha and theta defensins are absence in older vertebrates, like birds and fishes, indicates that defensins must have evolved from the same ancestral gene coding for β-defensins.

text: Although the same basic components are present in all vertebrate brains, some branches of vertebrate evolution have led to substantial distortions of brain geometry, especially in the forebrain area. The brain of a shark shows the basic components in a straightforward way, but in teleost fishes (the great majority of existing fish species), the forebrain has become "everted", like a sock turned inside out. In birds, there are also major changes in forebrain structure. These distortions can make it difficult to match brain components from one species with those of another species.

text: Although the same basic components are present in all vertebrate brains, some branches of vertebrate evolution have led to substantial distortions of brain geometry, especially in the forebrain area. The brain of a shark shows the basic components in a straightforward way, but in

text: teleost

text: fishes (the great majority of existing fish species), the forebrain has become "everted", like a sock turned inside out. In birds, there are also major changes in forebrain structure. These distortions can make it difficult to match brain components from one species with those of another species.

text: Jawed vertebrates and jawed fish evolved from jawless fish, and the cladogram below for jawed vertebrates is a continuation of the cladogram in the section above.

text: Jawed vertebrates and jawed fish evolved from jawless fish, and the

text: cladogram

text: below for jawed vertebrates is a continuation of the cladogram in the section above.

text: Endolymphatic infillings such as otoliths are structures in the saccule and utricle of the inner ear, specifically in the vestibular labyrinth of all vertebrates (fish, amphibians, reptiles, mammals and birds). In vertebrates, the saccule and utricle together make the otolith organs. Both statoconia and otoliths are used as gravity, balance, movement, and directional indicators in all vertebrates and have a secondary function in sound detection in higher aquatic and terrestrial vertebrates. They are sensitive to gravity and linear acceleration. Because of their orientation in the head, the utricle is sensitive to a change in horizontal movement, and the saccule gives information about vertical acceleration (such as when in an elevator).

text: Endolymphatic infillings such as otoliths are structures in the

text: saccule

text: and

text: utricle

text: of the

text: inner ear

text: , specifically in the

text: vestibular labyrinth

text: of all

text: vertebrates

text: (fish, amphibians, reptiles, mammals and birds). In vertebrates, the saccule and utricle together make the otolith organs. Both statoconia and otoliths are used as gravity, balance, movement, and directional indicators in all vertebrates and have a secondary function in sound detection in higher aquatic and terrestrial vertebrates. They are sensitive to

text: gravity

text: and linear

text: acceleration

text: . Because of their orientation in the head, the utricle is sensitive to a change in horizontal movement, and the saccule gives information about vertical acceleration (such as when in an

text: elevator

text: These are minute rounded or pyriform parasites found within erythrocytes, or other circulating or endothelial cells of vertebrates. The parasites reproduce by merogony without oocysts or spores.

text: These are minute rounded or pyriform parasites found within

text: erythrocytes

text: , or other circulating or

text: endothelial cell

text: s of

text: vertebrate

text: s. The parasites reproduce by

text: merogony

text: without

text: oocyst

text: s or

text: spore

text: s.

text: At its commencement, it is situated on the left of the vertebral column; it approaches the median line as it descends; and, at its termination, lies directly in front of the column.

text: Nidovirales are composed of (+) strand ssRNA (Group IV) viruses with vertebrate hosts.

text: Nidovirales

text: are composed of (+) strand ssRNA (Group IV) viruses with

text: vertebrate

text: hosts.

text: Northern lampreys (Petromyzontidae) have the highest number of chromosomes (164–174) among vertebrates.

text: Northern lampreys (Petromyzontidae) have the highest number of

text: chromosome

text: s (164–174) among vertebrates.

text: There are two IL17Rs (IL17RA and IL17RD) in the genome of the basal chordate Amphioxus. After two rounds of whole genome duplications, these two IL17R genes expanded into five early vertebrate IL17R genes, IL17RA to IL17RE. Two (IL17RA and IL17RD) are found in most vertebrates, whereas the other three (IL17RB, ILR17RC and IL17RE) have undergone some losses in vertebrates during evolution.

text: There are two IL17Rs (IL17RA and IL17RD) in the genome of the basal chordate

text: Amphioxus

text: . After two rounds of whole genome duplications, these two IL17R genes expanded into five early vertebrate IL17R genes, IL17RA to IL17RE. Two (IL17RA and IL17RD) are found in most vertebrates, whereas the other three (IL17RB, ILR17RC and IL17RE) have undergone some losses in vertebrates during evolution.

text: Modern reptiles exhibit some form of cold-bloodedness (i.e. some mix of poikilothermy, ectothermy, and bradymetabolism) so that they have limited physiological means of keeping the body temperature constant and often rely on external sources of heat. Due to a less stable core temperature than birds and mammals, reptilian biochemistry requires enzymes capable of maintaining efficiency over a greater range of temperatures than in the case for warm-blooded animals. The optimum body temperature range varies with species, but is typically below that of warm-blooded animals; for many lizards, it falls in the 24°–35 °C (75°–95 °F) range, while extreme heat-adapted species, like the American desert iguana Dipsosaurus dorsalis, can have optimal physiological temperatures in the mammalian range, between 35° and 40 °C (95° and 104 °F). While the optimum temperature is often encountered when the animal is active, the low basal metabolism makes body temperature drop rapidly when the animal is inactive.

text: Modern reptiles exhibit some form of

text: cold-bloodedness

text: (i.e. some mix of

text: poikilotherm

text: y,

text: ectotherm

text: y, and

text: bradymetabolism

text: ) so that they have limited physiological means of keeping the body temperature constant and often rely on external sources of heat. Due to a less stable core temperature than

text: bird

text: s and

text: mammal

text: s, reptilian biochemistry requires

text: enzyme

text: s capable of maintaining efficiency over a greater range of temperatures than in the case for

text: warm-blooded

text: animals. The optimum body temperature range varies with species, but is typically below that of warm-blooded animals; for many lizards, it falls in the 24°–35 °C (75°–95 °F) range, while extreme heat-adapted species, like the American

text: desert iguana

text: Dipsosaurus dorsalis, can have optimal physiological temperatures in the mammalian range, between 35° and 40 °C (95° and 104 °F). While the optimum temperature is often encountered when the animal is active, the low basal metabolism makes body temperature drop rapidly when the animal is inactive.

text: During embryogenesis the precursor to bone development is cartilage. Much of this substance is then replaced by bone during the second and third trimester, after the flesh such as muscle has formed around it; forming the skeleton. Cartilage is a stiff and inflexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs. It is not as hard and rigid as bone but is stiffer and less flexible than muscle.

text: During

text: embryogenesis

text: the precursor to bone development is

text: cartilage

text: . Much of this substance is then replaced by bone during the second and third trimester, after the flesh such as muscle has formed around it; forming the skeleton. Cartilage is a stiff and inflexible

text: connective tissue

text: found in many areas in the bodies of humans and other animals, including the joints between

text: bone

text: s, the

text: rib cage

text: , the

text: ear

text: , the

text: nose

text: , the elbow, the knee, the ankle, the

text: bronchial tubes

text: and the

text: intervertebral disc

text: s. It is not as hard and rigid as

text: bone

text: but is stiffer and less flexible than

text: muscle

text: The ciliary photoreceptor cells are located in the deep brain of the larva. They are not shaded by pigment and thus serve a non-directional light perception task. The ciliary photoreceptor cells resemble molecularly and morphologically the rods and cones of the human eye. Additional, they express an opsin that is more similar of vertebrate rod and cone visual ciliary opsins than those of invertebrate visual rhabdomeric opsins. Therefore, it is thought that the urbilaterain, the last common ancestor of mollusks, arthropods, and vertebrates already had ciliary photoreceptor cells.

text: The ciliary photoreceptor cells are located in the deep brain of the larva. They are not shaded by

text: pigment

text: and thus serve a non-directional light perception task. The ciliary photoreceptor cells resemble molecularly and morphologically the

text: rods

text: and

text: cones

text: of the human

text: eye

text: . Additional, they express an

text: opsin

text: that is more similar of vertebrate rod and cone visual ciliary opsins than those of invertebrate visual rhabdomeric opsins. Therefore, it is thought that the urbilaterain, the last common ancestor of

text: mollusk

text: s,

text: arthropod

text: s, and

text: vertebrate

text: s already had ciliary photoreceptor cells.

text: Salps appear to have a form preliminary to vertebrates, and are used as a starting point in models of how vertebrates evolved. Scientists speculate that the tiny groups of nerves in salps are one of the first instances of a primitive nervous system, which eventually evolved into the more complex central nervous systems of vertebrates.

text: Salps appear to have a form preliminary to vertebrates, and are used as a starting point in models of how vertebrates evolved. Scientists speculate that the tiny groups of nerves in salps are one of the first instances of a primitive

text: nervous system

text: , which eventually evolved into the more complex

text: central nervous system

text: s of vertebrates.

text: Like all Plasmodium species P. jiangi has both vertebrate and insect hosts. The vertebrate hosts for this parasite are birds.

text: Like all Plasmodium species P. jiangi has both

text: vertebrate

text: and

text: insect

text: bird

text: s.

text: They communicate through small openings on the front and sides of the vertebral bodies with the anterior external vertebral plexuses, and converge behind to the principal canal, which is sometimes double toward its posterior part, and open by valved orifices into the transverse branches which unite the anterior internal vertebral plexuses.

text: They communicate through small openings on the front and sides of the vertebral bodies with the

text: anterior external vertebral plexuses

text: , and converge behind to the

text: principal canal

text: , which is sometimes double toward its posterior part, and open by valved orifices into the transverse branches which unite the

text: anterior internal vertebral plexuses

text: The vertebral vein is formed in the suboccipital triangle, from numerous small tributaries which spring from the internal vertebral venous plexuses and issue from the vertebral canal above the posterior arch of the atlas.

text: The vertebral vein is formed in the

text: suboccipital triangle

text: , from numerous small tributaries which spring from the

text: internal vertebral venous plexuses

text: and issue from the

text: vertebral canal

text: above the posterior arch of the

text: atlas

text: → Example:  where did endothermy evolve in the lineage that led to mammals?

text: → Example:  where did

text: endothermy

text: evolve in the lineage that led to mammals?

text: Animals like sponges and coral colonies naturally fragment and reproduce. Many species of annelids  and flat worms reproduce by this method.

text: Animals like

text: sponges

text: and

text: coral

text: colonies naturally fragment and reproduce. Many species of

text: annelids

text: and flat worms reproduce by this method.

text: Vertebrates are the only chordate group to exhibit a proper brain. A slight swelling of the anterior end of the dorsal nerve cord is found in the lancelet, though it lacks the eyes and other complex sense organs comparable to those of vertebrates. Other chordates do not show any trends towards cephalisation. The central nervous system is based on a hollow nerve tube running along the length of the animal, from which the peripheral nervous system branches out to innervate the various systems. The front end of the nerve tube is expanded by a thickening of the walls and expansion of the central canal of spinal cord into three primary brain vesicles: The prosencephalon (forebrain), mesencephalon (midbrain) and rhombencephalon (hindbrain), further differentiated in the various vertebrate groups. Two laterally placed eyes form around outgrows from the midbrain, except in hagfish, though this may be a secondary loss. The forebrain is well developed and subdivided in most tetrapods, while the midbrain dominate in many fish and some salamanders. Vesicles of the forebrain are usually paired, giving rise to hemispheres like the cerebral hemispheres in mammals. The resulting anatomy of the central nervous system, with a single, hollow ventral nerve cord topped by a series of (often paired) vesicles is unique to vertebrates.

text: Vertebrates are the only

text: chordate

text: group to exhibit a proper

text: brain

text: . A slight swelling of the anterior end of the

text: dorsal nerve cord

text: is found in the

text: lancelet

text: , though it lacks the eyes and other complex sense organs comparable to those of vertebrates. Other chordates do not show any trends towards cephalisation. The

text: central nervous system

text: is based on a hollow nerve tube running along the length of the animal, from which the

text: peripheral nervous system

text: branches out to innervate the various systems. The front end of the nerve tube is expanded by a thickening of the walls and expansion of the

text: central canal of spinal cord

text: into three primary brain vesicles: The

text: prosencephalon

text: (forebrain),

text: mesencephalon

text: (midbrain) and

text: rhombencephalon

text: (hindbrain), further differentiated in the various vertebrate groups. Two laterally placed

text: eye

text: s form around outgrows from the midbrain, except in

text: hagfish

text: , though this may be a secondary loss. The forebrain is well developed and subdivided in most

text: tetrapod

text: s, while the midbrain dominate in many

text: fish

text: and some

text: salamander

text: s. Vesicles of the forebrain are usually paired, giving rise to hemispheres like the

text: cerebral hemisphere

text: s in

text: mammals

text: . The resulting anatomy of the central nervous system, with a single, hollow

text: ventral nerve cord

text: topped by a series of (often paired) vesicles is unique to vertebrates.

text: - launch and support international projects in the field of vertebrate palaeontology with a European contribution- encourage and assist students to take part in such projects to create an improved source of future vertebrate palaeontologists- set up or organise funds from European foundations and other sponsors- maintain a plurality of methods- encourage contacts and collaboration between European vertebrate palaeontologists by supporting each year the organisation of the Workshop of the EAVP in a different European country, in a historical continuity of the European Workshop on Vertebrate Palaeontology.

text: First the cartilage defect is exposed and cleaned whereby all unstable degenerated cartilage, including the calcified cartilage layer, are carefully removed. An imprint of the defect is then taken using a sterile moldable material (e.g. aluminium foil) and transferred to the collagen membrane which is cut to shape. The surgeon then creates tiny holes/fractures in the subchondral bone plate (microfracturing) with a special awl. Blood and bone marrow (containing stem cells) are released forming a blood clot which contains cartilage forming elements. The correctly sized collagen membrane is added to the microfractured area either by fibrin glue (autologous or commercially available) or suturing. Through flexion of the joint, the stable positioning of the membrane is verified and the wound is closed.

text: First the cartilage defect is exposed and cleaned whereby all unstable degenerated cartilage, including the calcified cartilage layer, are carefully removed. An imprint of the defect is then taken using a

text: sterile

text: moldable material (e.g.

text: aluminium foil

text: ) and transferred to the collagen membrane which is cut to shape. The surgeon then creates tiny holes/fractures in the

text: subchondral bone

text: plate (

text: microfracturing

text: ) with a special

text: awl

text: Blood

text: and

text: bone marrow

text: (containing

text: stem cell

text: s) are released forming a

text: blood clot

text: which contains cartilage forming elements. The correctly sized collagen membrane is added to the microfractured area either by

text: fibrin glue

text: autologous

text: or commercially available) or

text: suturing

text: . Through flexion of the joint, the stable positioning of the membrane is verified and the wound is closed.

text: Unlike vertebrates, cnidarians have no other distinctive axes. "Lateral", "dorsal", and "ventral" have no meaning in such organisms, and all can be replaced by the generic term peripheral (, "around"). Medial can be used, but in the case of radiates indicates the central point, rather than a central axis as in vertebrates. Thus, there are multiple possible radial axes and medio-peripheral (half-) axes. However, it is noteworthy that some biradially symmetrical comb jellies do have distinct "tentacular" and "pharyngeal" axes and are thus anatomically equivalent to bilaterally symmetrical animals.

text: Unlike vertebrates, cnidarians have no other distinctive axes. "Lateral", "dorsal", and "ventral" have no meaning in such organisms, and all can be replaced by the generic term peripheral (, "around"). Medial can be used, but in the case of radiates indicates the central point, rather than a central axis as in vertebrates. Thus, there are multiple possible radial axes and medio-peripheral (half-) axes. However, it is noteworthy that some biradially symmetrical

text: comb jellies

text: do have distinct "tentacular" and "pharyngeal" axes and are thus anatomically equivalent to

text: bilaterally symmetrical

text: animals.

text: The vertebral column consisted of ten cervical (neck), twelve dorsal, six fused sacral and an unknown number of caudal (tail) vertebrae. The neck was nearly straight, rather than having the S-curve seen in other theropods, and also unusually wide, especially towards its base. The top of the neck's spinal column featured a double row of enlarged, upwardly directed bony processes called epipophyses, creating a smooth trough on the top of the neck vertebrae. These processes were the highest points of the spine, towering above the unusually low spinous processes. The epipophyses probably provided attachment areas for a markedly strong neck musculature. A similar double row was also present in the tail, formed there by highly modified caudal ribs, in front view protruding upwards in a V-shape, their inner sides creating a smooth, flat, top surface of the front tail vertebrae. The end of each caudal rib was furnished with a forward projecting hook-shaped expansion that connected to the caudal rib of the preceding vertebra.

text: The vertebral column consisted of ten cervical (neck), twelve dorsal, six fused sacral and an unknown number of caudal (tail) vertebrae. The neck was nearly straight, rather than having the S-curve seen in other theropods, and also unusually wide, especially towards its base. The top of the neck's spinal column featured a double row of enlarged, upwardly directed bony processes called

text: epipophyses

text: , creating a smooth trough on the top of the neck vertebrae. These processes were the highest points of the spine, towering above the unusually low

text: spinous process

text: es. The epipophyses probably provided attachment areas for a markedly strong neck musculature. A similar double row was also present in the tail, formed there by highly modified

text: caudal ribs

text: , in front view protruding upwards in a V-shape, their inner sides creating a smooth, flat, top surface of the front tail vertebrae. The end of each caudal rib was furnished with a forward projecting hook-shaped expansion that connected to the caudal rib of the preceding vertebra.

text: An endoskeleton is a skeleton that is on the inside of a body. The endoskeleton develops within the skin or in the deeper body tissues. The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage). During early embryonic development the endoskeleton is composed of notochord and cartilage. The notochord in most vertebrates is replaced by the vertebral column and cartilage is replaced by bone in most adults. In three phyla and one subclass of animals, endoskeletons of various complexity are found: Chordata, Echinodermata, Porifera, and Coleoidea. An endoskeleton may function purely for support (as in the case of sponges), but often serves as an attachment site for muscle and a mechanism for transmitting muscular forces. A true endoskeleton is derived from mesodermal tissue. Such a skeleton is present in echinoderms and chordates. The poriferan 'skeleton' consists of microscopic calcareous or siliceous spicules or a spongin network. The Coleoidae do not have a true endoskeleton in the evolutionary sense; there, a mollusk exoskeleton evolved into several sorts of internal structure, the "cuttlebone" of cuttlefish being the best-known version. Yet they do have cartilaginous tissue in their body, even if it is not mineralized, especially in the head, where it forms a primitive cranium.The endoskeleton gives shape, support, and protection to the body and provides a means of locomotion.

text: An endoskeleton is a skeleton that is on the inside of a body. The endoskeleton develops within the skin or in the deeper body tissues. The vertebrate endoskeleton is basically made up of two types of tissues (

text: bone

text: and

text: cartilage

text: ). During early embryonic development the endoskeleton is composed of

text: notochord

text: and cartilage. The notochord in most vertebrates is replaced by the vertebral column and cartilage is replaced by bone in most adults. In three

text: phyla

text: and one

text: subclass

text: of animals, endoskeletons of various complexity are found:

text: Chordata

text: Echinoderm

text: ata,

text: Porifera

text: , and

text: Coleoidea

text: . An endoskeleton may function purely for support (as in the case of

text: sponges

text: ), but often serves as an attachment site for muscle and a mechanism for transmitting muscular forces. A true endoskeleton is derived from

text: mesodermal

text: tissue. Such a

text: skeleton

text: is present in echinoderms and chordates. The poriferan 'skeleton' consists of microscopic calcareous or siliceous

text: spicule

text: s or a

text: spongin

text: network. The Coleoidae do not have a true endoskeleton in the evolutionary sense; there, a

text: mollusk

text: exoskeleton

text: evolved

text: into several sorts of internal structure, the "cuttlebone" of

text: cuttlefish

text: being the best-known version. Yet they do have cartilaginous tissue in their body, even if it is not mineralized, especially in the head, where it forms a primitive cranium.The endoskeleton gives shape, support, and protection to the body and provides a means of locomotion.

text: Additional functions of the gracile fasciculus include carrying deep touch, vibrational, and visceral pain information to the brainstem.  The gracile fasciculus and the cuneate fasciculus offer the same functions but can be differentiated by the vertebral level at which information is provided.  The cuneate fasciculus carries information from vertebral level T6 and above, and the gracile fasciculus carries information from vertebral levels T7 and below. The two ascending tracts meet at the T6 level.

text: Additional functions of the gracile fasciculus include carrying deep touch, vibrational, and visceral pain information to the brainstem.  The gracile fasciculus and the

text: cuneate fasciculus

text: offer the same functions but can be differentiated by the vertebral level at which information is provided.  The cuneate fasciculus carries information from vertebral level

text: and above, and the gracile fasciculus carries information from vertebral levels

text: and below. The two ascending tracts meet at the T6 level.

text: All vertebrates (including humans) have the same basic body plan they are strictly bilaterally symmetrical in early embryonic stages and largely bilaterally symmetrical in adulthood. That is, they have mirror-image left and right halves if divided down the centre. For these reasons, the basic directional terms can be considered to be those used in vertebrates. By extension, the same terms are used for many other (invertebrate) organisms as well.

text: All

text: vertebrate

text: s (including humans) have the same basic

text: body plan

text: they are strictly

text: bilaterally symmetrical

text: in early embryonic stages and largely bilaterally symmetrical in adulthood. That is, they have mirror-image left and right halves if divided down the centre. For these reasons, the basic directional terms can be considered to be those used in vertebrates. By extension, the same terms are used for many other (

text: invertebrate

text: ) organisms as well.

text: In most cases bone development is complex; it follows the formation of a first skeleton of cartilage made by chondrocytes, which is then removed and replaced by bone, made by osteoblasts.

text: In most cases bone development is complex; it follows the formation of a first skeleton of

text: cartilage

text: made by chondrocytes, which is then removed and replaced by bone, made by osteoblasts.

text: Invertebrates are animals  without a vertebral column. This has led to the conclusion that invertebrates are a group that deviates from the normal, vertebrates. This has been said to be because researchers in the past, such as Lamarck, viewed vertebrates as a "standard": in Lamarck's theory of evolution, he believed that characteristics acquired through the evolutionary process involved not only survival, but also progression toward a "higher form", to which humans and vertebrates were closer than invertebrates were. Although goal-directed evolution has been abandoned, the distinction of invertebrates and vertebrates persists to this day, even though the grouping has been noted to be "hardly natural or even very sharp." Another reason cited for this continued distinction is that Lamarck created a precedent through his classifications which is now difficult to escape from. It is also possible that some humans believe that, they themselves being vertebrates, the group deserves more attention than invertebrates. In any event, in the 1968 edition of Invertebrate Zoology, it is noted that "division of the Animal Kingdom into vertebrates and invertebrates is artificial and reflects human bias in favor of man's own relatives." The book also points out that the group lumps a vast number of species together, so that no one characteristic describes all invertebrates. In addition, some species included are only remotely related to one another, with some more related to vertebrates than other invertebrates (see Paraphyly).

text: Paraphyly

text: Although the spinal cord cell bodies end around the L1/L2 vertebral level, the spinal nerves for each segment exit at the level of the corresponding vertebra. For the nerves of the lower spinal cord, this means that they exit the vertebral column much lower (more caudally) than their roots. As these nerves travel from their respective roots to their point of exit from the vertebral column, the nerves of the lower spinal segments form a bundle called the cauda equina.

text: Spondylarthropathy is any form of arthropathy of the vertebral column.<ref>thefreedictionary.com/spondyloarthropathy citing:

text: Spondylarthropathy

text: is any form of arthropathy of the

text: vertebral column

text: .<ref>thefreedictionary.com/spondyloarthropathy citing:

text: The vertebrate jaw probably originally evolved in the Silurian period and appeared in the Placoderm fish which further diversified in the Devonian. The two most anterior pharyngeal arches are thought to have become the jaw itself and the hyoid arch, respectively.  The hyoid system suspends the jaw from the braincase of the skull, permitting great mobility of the jaws.  While there is no fossil evidence directly to support this theory, it makes sense in light of the numbers of pharyngeal arches that are visible in extant jawed vertebrates (the Gnathostomes), which have seven arches, and primitive jawless vertebrates (the Agnatha), which have nine.

text: Silurian

text: period and appeared in the

text: Placoderm

text: fish

text: which further diversified in the

text: Devonian

text: . The two most anterior

text: pharyngeal arch

text: es are thought to have become the jaw itself and the hyoid arch, respectively.  The hyoid system suspends the jaw from the braincase of the skull, permitting great mobility of the jaws.  While there is no fossil evidence directly to support this theory, it makes sense in light of the numbers of pharyngeal arches that are visible in extant jawed vertebrates (the

text: Gnathostomes

text: Agnatha

text: ), which have nine.

text: Osteochondropathy refers to a disease ("-pathy") of the bone and cartilage.

text: Osteochondropathy refers to a

text: disease

text: ("-pathy") of the

text: bone

text: and

text: cartilage

text: Vertebral osteomyelitis (also termed spinal osteomyelitis, spondylodiskitis, or disk-space infection), is a type of osteomyelitis (which is infection and inflammation of the bone and bone marrow). Vertebral osteomyelitis is a rare bone infection concentrated in the spinal region. Cases of vertebral osteomyelitis are so rare that only 2-4% of all bone infections are attributed to the disease. The infection can be classified as acute or chronic depending on the severity of the onset of the case, where acute patients often experience better outcomes than those living with the chronic symptoms that are characteristic of the disease. Although vertebral osteomyelitis is found in patients across a wide range of ages, the infection is commonly reported in young children and older adults. Vertebral osteomyelitis often attacks two vertebrae and the corresponding intervertebral disk, causing narrowing of the disc space between the vertebrae. The prognosis for the disease is dependent on where the infection is concentrated in the spine, the time between initial onset and treatment, and what approach is used to treat the disease.

text: Vertebral osteomyelitis (also termed spinal osteomyelitis, spondylodiskitis, or disk-space infection), is a type of

text: osteomyelitis

text: (which is infection and inflammation of the

text: bone

text: and

text: bone marrow

text: ). Vertebral osteomyelitis is a rare bone infection concentrated in the spinal region. Cases of vertebral osteomyelitis are so rare that only 2-4% of all bone infections are attributed to the disease. The infection can be classified as acute or chronic depending on the severity of the onset of the case, where acute patients often experience better outcomes than those living with the chronic symptoms that are characteristic of the disease. Although vertebral osteomyelitis is found in patients across a wide range of ages, the infection is commonly reported in young children and older adults. Vertebral osteomyelitis often attacks two

text: vertebrae

text: and the corresponding intervertebral disk, causing narrowing of the disc space between the vertebrae. The prognosis for the disease is dependent on where the infection is concentrated in the

text: spine

text: , the time between initial onset and treatment, and what approach is used to treat the disease.

text: There are about 50,000 species of animals that have a vertebral column. The human vertebral column is one of the most-studied examples.

text: The skeleton, which forms the support structure inside the fish is either made of cartilage as in the (Chondrichthyes), or bones as in the (Osteichthyes). The main skeletal element is the vertebral column, composed of articulating vertebrae which are lightweight yet strong. The ribs attach to the spine and there are no limbs or limb girdles. They are supported only by the muscles. The main external features of the fish, the fins, are composed of either bony or soft spines called rays, which with the exception of the caudal fin (tail fin), have no direct connection with the spine. They are supported by the muscles which compose the main part of the trunk.

text: The skeleton, which forms the support structure inside the

text: fish

text: is either made of

text: cartilage

text: as in the (

text: Chondrichthyes

text: ), or bones as in the (

text: Osteichthyes

text: ). The main skeletal element is the vertebral column, composed of articulating vertebrae which are lightweight yet strong. The ribs attach to the spine and there are no limbs or limb girdles. They are supported only by the muscles. The main external features of the fish, the

text: fins

text: , are composed of either bony or soft spines called rays, which with the exception of the caudal fin (tail fin), have no direct connection with the spine. They are supported by the muscles which compose the main part of the trunk.

text: A number of observations associated with neutral mutation were predicted in neutral theory including:  amino acids with similar biochemical properties should be substituted more often than biochemically different amino acids; synonymous base substitutions should be observed more often than nonsynonymous substitutions; introns should evolve at the same rate as synonymous mutations in coding exons;  and pseudogenes should also evolve at a similar rate. These predictions have been confirmed with the introduction of additional genetic data since the theory’s introduction.

text: A number of observations associated with neutral mutation were predicted in neutral theory including:  amino acids with similar biochemical properties should be substituted more often than biochemically different amino acids; synonymous base substitutions should be observed more often than nonsynonymous substitutions;

text: intron

text: s should evolve at the same rate as synonymous mutations in coding

text: exon

text: s;  and

text: pseudogenes

text: should also evolve at a similar rate. These predictions have been confirmed with the introduction of additional genetic data since the theory’s introduction.

text: Armand de Ricqlès discovered Haversian canals in dinosaur bones, and argued that they were evidence of endothermy in dinosaurs. These canals are common in "warm-blooded" animals and are associated with fast growth and an active life style because they help to recycle bone to facilitate rapid growth and repair damage caused by stress or injuries. Dense secondary Haversian bone, which is formed during remodeling, is found in many living endotherms as well as dinosaurs, pterosaurs and therapsids. Secondary Haversian canals are correlated with size and age, mechanical stress and nutrient turnover. The presence of secondary Haversian canals suggests comparable bone growth and lifespans in mammals and dinosaurs. Bakker argued that the presence of fibrolamellar bone (produced quickly and having a fibrous, woven appearance) in dinosaur fossils was evidence of endothermy.

text: Armand de Ricqlès discovered

text: Haversian canals

text: in dinosaur bones, and argued that they were evidence of endothermy in dinosaurs. These canals are common in "warm-blooded" animals and are associated with fast growth and an active life style because they help to recycle bone to facilitate rapid growth and repair damage caused by stress or injuries. Dense secondary Haversian bone, which is formed during remodeling, is found in many living endotherms as well as dinosaurs, pterosaurs and therapsids. Secondary Haversian canals are correlated with size and age, mechanical stress and nutrient turnover. The presence of secondary Haversian canals suggests comparable bone growth and lifespans in mammals and dinosaurs. Bakker argued that the presence of fibrolamellar bone (produced quickly and having a fibrous, woven appearance) in dinosaur fossils was evidence of endothermy.

text: Certain species of fish maintain elevated body temperatures. Endothermic teleosts (bony fish) are all in the suborder Scombroidei and include the billfishes, tunas, and one species of "primitive" mackerel (Gasterochisma melampus). All sharks in the family Lamnidae – shortfin mako, long fin mako, white, porbeagle, and salmon shark – are endothermic, and evidence suggests the trait exists in family Alopiidae (thresher sharks). The degree of endothermy varies from the billfish, which warm only their eyes and brain, to bluefin tuna and porbeagle sharks who maintain body temperatures elevated in excess of 20 °C above ambient water temperatures. See also gigantothermy. Endothermy, though metabolically costly, is thought to provide advantages such as increased muscle strength, higher rates of central nervous system processing, and higher rates of digestion.

text: Certain species of fish maintain elevated body temperatures.

text: Endothermic

text: teleost

text: s (bony fish) are all in the suborder

text: Scombroidei

text: and include the

text: billfish

text: es, tunas, and one species of "primitive"

text: mackerel

text: (Gasterochisma melampus). All sharks in the family

text: Lamnidae

text: – shortfin mako, long fin mako, white, porbeagle, and salmon shark – are endothermic, and evidence suggests the trait exists in family

text: Alopiidae

text: thresher sharks

text: ). The degree of endothermy varies from the

text: billfish

text: , which warm only their eyes and brain, to

text: bluefin tuna

text: and

text: porbeagle shark

text: s who maintain body temperatures elevated in excess of 20 °C above ambient water temperatures. See also

text: gigantothermy

text: . Endothermy, though metabolically costly, is thought to provide advantages such as increased muscle strength, higher rates of central

text: nervous system

text: processing, and higher rates of

text: digestion

text: A craniate is a member of Craniata (sometimes Craniota), a proposed clade of chordate animals that contains the Myxini (hagfish), Petromyzontida (including lampreys), and Gnathostomata (jawed vertebrates) as living representatives. As the name suggests, craniates are animals with a (hard bone or cartilage) skull in phylum Chordata.

text: A craniate is a member of Craniata (sometimes Craniota), a proposed

text: clade

text: of

text: chordate

text: animal

text: s that contains the

text: Myxini

text: (hagfish),

text: Petromyzontida

text: (including

text: lamprey

text: s), and

text: Gnathostomata

text: (jawed vertebrates) as living representatives. As the name suggests, craniates are animals with a (hard

text: bone

text: or

text: cartilage

text: skull

text: in phylum Chordata.

text: In vertebrates, the first part of the digestive system is the buccal cavity, commonly known as the mouth. The buccal cavity of a fish is separated from the opercular cavity by the gills. Water flows in through the mouth, passes over the gills and exits via the operculum or gill slits. Nearly all fish have jaws and may seize food with them but most feed by opening their jaws, expanding their pharynx and sucking in food items. The food may be held or chewed by teeth located in the jaws, on the roof of the mouth, on the pharynx or on the gill arches.

text: In vertebrates, the first part of the digestive system is the

text: buccal cavity

text: , commonly known as the mouth. The buccal cavity of a fish is separated from the opercular cavity by the gills. Water flows in through the mouth, passes over the gills and exits via the

text: operculum

text: or

text: gill slit

text: s. Nearly all fish have

text: jaws

text: and may seize food with them but most feed by opening their jaws, expanding their pharynx and sucking in food items. The food may be held or chewed by teeth located in the jaws, on the roof of the mouth, on the pharynx or on the

text: gill arch

text: es.

text: The group is characterized by retaining the primitive vertebrate condition in several traits:

text: Dinosaurs are a varied group of animals from taxonomic, morphological and ecological standpoints. Birds, at over 10,000 living species, are the most diverse group of vertebrates besides perciform fish. Using fossil evidence, paleontologists have identified over 500 distinct genera and more than 1,000 different species of non-avian dinosaurs.

text: Dinosaurs are a varied group of animals from

text: taxonomic

text: morphological

text: and

text: ecological

text: standpoints. Birds, at over 10,000 living species, are the most diverse group of vertebrates besides

text: perciform

text: fish. Using fossil evidence,

text: paleontologists

text: have identified over 500 distinct

text: genera

text: and more than 1,000 different species of non-avian dinosaurs.

text: The colour of Lucasium stenodactylum varies from reddish brown to brown. The length of most individuals is approximately . Body patterns also vary, although the species is typically found with a cream or white vertebral stripe. The stripe starts at each eye and joins at the back of the neck into a single vertebral stripe. In some individuals the vertebral stripe may be pale or absent. Large and small pale spots may be found on the limbs and sides of the body. Whitish under body. Tail is slender and comprises about 80 percent of snout-vent length. Homogeneous dorsal and flank scales.

text: In the upper part of the vertebral column, spinal nerves exit directly from the spinal cord, whereas in the lower part of the vertebral column nerves pass further down the column before exiting. The terminal portion of the spinal cord is called the conus medullaris. The pia mater continues as an extension called the filum terminale, which anchors the spinal cord to the coccyx. The cauda equina (“horse’s tail”) is the name for the collection of nerves in the vertebral column that continue to travel through the vertebral column below the conus medullaris. The cauda equina forms as a result of the fact that the spinal cord stops growing in length at about age four, even though the vertebral column continues to lengthen until adulthood. This results in the fact that sacral spinal nerves actually originate in the upper lumbar region. The spinal cord can be anatomically divided into 31 spinal segments based on the origins of the spinal nerves.

text: Meanwhile, Dr. Anne Glass decides to perform an autopsy on the corpse of the Skitter she killed, which she hasn't had a chance to perform yet because of the temporary evacuation instigated by the incident with the 7th Mass. All previous attempts to perform autopsies on dead Skitters have been unsuccessful, because their innards rapidly decompose into unrecognizable mush very soon after they die.  In the first months of the invasion the humans were just running for their lives and couldn't carry Skitter corpses back from the front lines, and even when they could bring one back later on, they had already decomposed internally.  Because the captured Skitter died right inside of their base, it's their first real opportunity to successfully autopsy one.  Lourdes assists Anne with the procedure, because as a first year medical student she's the closest thing to a nurse she has.  They discover that while the Skitters have tough leathery skin and carapace armor, their internal structure isn't that much different from terrestrial vertebrates, including an endoskeleton, cardio-vascular system, and nervous system.  Anne then confirms her fears when she saws through the armored carapace of the Skitter's back, and finds that it has a harness attached to its spine, identical in structure to the ones attached to the human children.  The implications to Anne are clear:  the Skitters were themselves harnessed, and might not always have been Skitters.  Particularly because the harness was found within their outer carapace, it seems that they used to be some other kind of lifeform, captured by the tall humanoid aliens who used the harnesses to mutate them into shock-troops.  Anne realizes this means that the harnessed children are being slowly mutated, either into Skitters or something like them.

text: Meanwhile, Dr. Anne Glass decides to perform an autopsy on the corpse of the Skitter she killed, which she hasn't had a chance to perform yet because of the temporary evacuation instigated by the incident with the 7th Mass. All previous attempts to perform autopsies on dead Skitters have been unsuccessful, because their innards rapidly decompose into unrecognizable mush very soon after they die.  In the first months of the invasion the humans were just running for their lives and couldn't carry Skitter corpses back from the front lines, and even when they could bring one back later on, they had already decomposed internally.  Because the captured Skitter died right inside of their base, it's their first real opportunity to successfully autopsy one.  Lourdes assists Anne with the procedure, because as a first year medical student she's the closest thing to a nurse she has.  They discover that while the Skitters have tough leathery skin and carapace armor, their internal structure isn't that much different from terrestrial vertebrates, including an

text: endoskeleton

text: cardio-vascular system

text: , and

text: nervous system

text: .  Anne then confirms her fears when she saws through the armored carapace of the Skitter's back, and finds that it has a harness attached to its spine, identical in structure to the ones attached to the human children.  The implications to Anne are clear:  the Skitters were themselves harnessed, and might not always have been Skitters.  Particularly because the harness was found within their outer carapace, it seems that they used to be some other kind of lifeform, captured by the tall humanoid aliens who used the harnesses to mutate them into shock-troops.  Anne realizes this means that the harnessed children are being slowly mutated, either into Skitters or something like them.

text: This list of fossil fishes described in 2017 is a list of new taxa of jawless vertebrates, placoderms, acanthodians, fossil cartilaginous fishes, bony fishes and other fishes of every kind that are scheduled to be described during the year 2017, as well as other significant discoveries and events related to paleontology of fishes that are scheduled to occur in the year 2017. The list only includes taxa at the level of genus or species.

text: This list of

text: fossil

text: fishes

text: described in 2017 is a list of new

text: taxa

text: of

text: jawless vertebrates

text: placoderm

text: s,

text: acanthodians

text: , fossil

text: cartilaginous fishes

text: bony fishes

text: and other fishes of every kind that are scheduled to be

text: described

text: during the year 2017, as well as other significant discoveries and events related to

text: paleontology

text: of fishes that are scheduled to occur in the year 2017. The list only includes taxa at the level of

text: genus

text: or

text: species

text: Among vertebrates the most abundant and diverse group are fish. The presence of mostly articulated skeletons, exceptional preservation of tissue and lack of any other signs of transportation may indicate that these are demic and autochthonous entities (meaning that they lived and died in the same place where they fossilized).

text: Among

text: vertebrates

text: the most abundant and diverse group are

text: fish

text: . The presence of mostly articulated skeletons, exceptional preservation of tissue and lack of any other signs of transportation may indicate that these are demic and autochthonous entities (meaning that they lived and died in the same place where they fossilized).

text: This list of fossil fishes described in 2015 is a list of new taxa of jawless vertebrates, placoderms, acanthodians, fossil cartilaginous fishes, bony fishes and other fishes of every kind that have been described during the year 2015, as well as other significant discoveries and events related to paleontology of fishes that occurred in the year 2015. The list only includes taxa at the level of genus or species.

text: This list of

text: fossil

text: fishes

text: described in 2015 is a list of new

text: taxa

text: of

text: jawless vertebrates

text: placoderm

text: s,

text: acanthodians

text: , fossil

text: cartilaginous fishes

text: bony fishes

text: described

text: during the year 2015, as well as other significant discoveries and events related to

text: paleontology

text: of fishes that occurred in the year 2015. The list only includes taxa at the level of

text: genus

text: or

text: species

text: Over half of all living vertebrate species (about 32,000 species) are fish (non-tetrapod craniates), a diverse set of lineages that inhabit all the world's aquatic ecosystems, from snow minnows (Cypriniformes) in Himalayan lakes at elevations over  to flatfishes (order Pleuronectiformes) in the Challenger Deep, the deepest ocean trench at about . Fishes of myriad varieties are the main predators in most of the world's water bodies, both freshwater and marine. The rest of the vertebrate species are tetrapods, a single lineage that includes amphibians (with roughly 7,000 species); mammals (with approximately 5,500 species); and reptiles and birds (with about 20,000 species divided evenly between the two classes). Tetrapods comprise the dominant megafauna of most terrestrial environments and also include many partially or fully aquatic groups (e.g., sea snakes, penguins, cetaceans).

text: Over half of all living vertebrate species (about 32,000 species) are fish (non-tetrapod craniates), a diverse set of lineages that inhabit all the world's aquatic ecosystems, from snow minnows (Cypriniformes) in Himalayan lakes at elevations over  to flatfishes (order Pleuronectiformes) in the Challenger Deep, the deepest ocean trench at about . Fishes of myriad varieties are the main predators in most of the world's water bodies, both freshwater and marine. The rest of the vertebrate species are tetrapods, a single lineage that includes amphibians (with roughly 7,000 species); mammals (with approximately 5,500 species); and reptiles and birds (with about 20,000 species divided evenly between the two classes). Tetrapods comprise the dominant megafauna of most terrestrial environments and also include many partially or fully aquatic groups (e.g., sea

text: snakes

text: , penguins, cetaceans).

text: Carapace elevated, tectiform, the keel ;ending in a nodosity on the third vertebral shield; posterior margin not or but very slightly serrated; nuchal shield small, square or trapezoidal; first vertebral very variable in shape, usually with straight lateral borders diverging forwards in the half-grown specimens, narrower in front and with sinuous lateral borders in the adult; second vertebral as long as or a little longer than second, frequently obtusely pointed behind; third vertebral pointed behind, in contact with the point of the very elongate fourth; fifth vertebral broader than the others. Plastron large, strongly angulated laterally in the young, truncate anteriorly, angularly notched posteriorly; proportions of plastral shields very variable; suture between gulars and humerals forming a right angle; axillary and inguinal large. Head moderate ; 6nout short, rather pointed and prominent; jaws with denticulated edge, upper not notched mesially; alveolar surface of upper jaw with the median ridge nearer the inner than the outer border; bony choanae between the orbits ; the width of the lower jaw at the symphysis is less than the diameter of the orbit. Fore limbs with large transverse scales. Carapace olive, that of young with some black spots, especially on the posterior edge of the first three vertebrals; an orange vertebral band and a narrow yellow margin; carapace more uniform in the adult; plastron orange or red, with black spots, or brown with a yellowish anterior and lateral border to each shield, in one specimen uniform yellow. Head blackish; jaws and sides of crown orange; neck with numerous yellow lines on a blackish ground; limbs dark olive, spotted with yellow.Length of shell up to nearly 9 inches.

text: Overexploitation threatens one-third of endangered vertebrates, as well as other groups. Excluding edible fish, the illegal trade in wildlife is valued at $10 billion per year.  Industries responsible for this include the trade in bushmeat, the trade in Chinese medicine, and the fur trade. The Convention for International Trade in Endangered Species of Wild Fauna and Flora, or CITES was set up in order to control and regulate the trade in endangered animals.  It currently protects, to a varying degree, some 33,000 species of animals and plants. It is estimated that a quarter of the endangered vertebrates in the United States of America and half of the endangered mammals is attributed to overexploitation.

text: Overexploitation threatens one-third of endangered

text: vertebrate

text: s, as well as other groups. Excluding edible fish, the illegal trade in wildlife is valued at $10 billion per year.  Industries responsible for this include the trade in

text: bushmeat

text: , the trade in

text: Chinese medicine

text: , and the

text: fur trade

text: . The Convention for International Trade in Endangered Species of Wild Fauna and Flora, or

text: CITES

text: was set up in order to control and regulate the trade in endangered animals.  It currently protects, to a varying degree, some 33,000 species of animals and plants. It is estimated that a quarter of the endangered vertebrates in the United States of America and half of the endangered mammals is attributed to overexploitation.

text: A PhD thesis published in 2011, Vertebrate Diversity in the Bussaco Mountain and Surrounding Areas, documented research undertaken in the Serra do Buçaco and identified 56 species of mammals, birds, bats and amphibians found in Buçaco Forest.

text: Vertebrate zoology is the biological discipline that consists of the study of Vertebrate animals, i.e., animals with a backbone, such as fish, amphibians, reptiles, birds and mammals.

text: Vertebrate zoology is the

text: biological

text: discipline

text: that consists of the study of

text: Vertebrate

text: animals, i.e., animals with a

text: backbone

text: , such as

text: fish

text: amphibian

text: s,

text: reptile

text: s,

text: bird

text: s and

text: mammal

text: s.

text: Rotation is the most common form of displacement, and, in this case, the tip of the coffin bone rotates downward.  The degree of rotation may be influenced by the severity of the initial attack and the time of initiation and aggressiveness of treatment.  A combination of forces (e.g. the tension of the deep digital flexor tendon and the weight of the horse) result in the deep digital flexor tendon literally pulling the dorsal face of the coffin bone away from the inside of the hoof wall, which allows the coffin bone to rotate.  Also, ligaments attaching the collateral cartilages to the digit, primarily in the palmar portion of the foot, possibly contribute to a difference in support from front to back.  The body weight of the animal probably contributes to rotation of the coffin bone.  Rotation results in an obvious misalignment between PII (the short pastern bone) and PIII (the coffin bone).  If rotation of the third phalanx continues, its tip can eventually penetrate the sole of the foot.

text: The evolution of TBR1 has been studied in amphioxi, also known as lancelets. A T-box-containing cDNA was isolated in the lancelet Branchiostoma belcheri and found to possess a T-domain orthologous to that of the T-Brain subfamily of T-box genes, specifically TBR1. However, lancelets lack a true brain and no TBR1 transcripts were found in the neural tissue of the lancelet. This suggests that the neuronal role of TBR1 evolved in vertebrates after the lancelet lineage had already diverged from that of vertebrates.

text: The

text: evolution

text: of TBR1 has been studied in amphioxi, also known as

text: lancelets

text: . A T-box-containing cDNA was isolated in the lancelet Branchiostoma belcheri and found to possess a T-domain orthologous to that of the T-Brain subfamily of T-box genes, specifically TBR1. However, lancelets lack a true brain and no TBR1 transcripts were found in the neural tissue of the lancelet. This suggests that the neuronal role of TBR1 evolved in vertebrates after the lancelet lineage had already diverged from that of vertebrates.

text: These links are hard if not impossible to break because evolution usually requires that anatomy be formed by small consecutive modifications in populations through generations. In his book, Why We Get Sick, Dr. Randolph Nesse uses the "blind spot" in the vertebrate eye (caused by the nerve fibers running through the retina) as an example of this. He says that natural selection has come up with an elaborate work-around of the eyes wobbling back-and-forth to correct for this, but vertebrates have not found the solution embodied in cephalopod eyes, where the optic nerve does not interrupt the view. See also: Evolution of the eye.

text: These links are hard if not impossible to break because evolution usually requires that anatomy be formed by small consecutive modifications in populations through generations. In his book, Why We Get Sick, Dr.

text: Randolph Nesse

text: uses the

text: "blind spot"

text: in the vertebrate eye (caused by the nerve fibers running through the

text: retina

text: ) as an example of this. He says that

text: natural selection

text: has come up with an elaborate work-around of the eyes wobbling back-and-forth to correct for this, but vertebrates have not found the solution embodied in

text: cephalopod

text: eyes, where the optic nerve does not interrupt the view. See also:

text: Evolution of the eye

text: Coastal fishing villages are often somewhat isolated, and sited around a small natural harbour which provides safe haven for a village fleet of fishing boats. The village needs to provide a safe way of landing fish and securing boats when they are not in use. Fishing villages may operate from a beach, particularly around lakes. For example, around parts of Lake Malawi, each fishing village has its own beach. If a fisherman from outside the village lands fish on the beach, he gives some of the fish to the village headman. Village fishing boats are usually characteristic of the stretch of coast along which they operate. Traditional fishing boats evolve over time to meet the local conditions, such as the materials available locally for boat building, the type of sea conditions the boats will encounter, and the demands of the local fisheries.

text: Coastal fishing villages are often somewhat isolated, and sited around a small natural

text: harbour

text: which provides safe haven for a village fleet of

text: fishing boats

text: . The village needs to provide a safe way of landing fish and securing boats when they are not in use. Fishing villages may operate from a beach, particularly around lakes. For example, around parts of

text: Lake Malawi

text: , each fishing village has its own beach. If a fisherman from outside the village lands fish on the beach, he gives some of the fish to the village headman. Village fishing boats are usually characteristic of the stretch of coast along which they operate.

text: Traditional fishing boats

text: evolve over time to meet the local conditions, such as the materials available locally for boat building, the type of sea conditions the boats will encounter, and the demands of the local

text: fisheries

text: In Late Devonian vertebrate speciation, descendants of pelagic lobe-finned fish – like Eusthenopteron – exhibited a sequence of adaptations: Panderichthys, suited to muddy shallows; Tiktaalik with limb-like fins that could take it onto land; stem-tetrapods in weed-filled swamps, such as Acanthostega, which had eight-digited feet; and Ichthyostega, with full limbs. Their descendants also included pelagic lobe-finned fish such as coelacanth species.

text: In

text: Late Devonian

text: vertebrate

text: speciation, descendants of

text: pelagic

text: lobe-finned fish

text: – like

text: Eusthenopteron

text: – exhibited a sequence of adaptations:

text: Panderichthys

text: , suited to muddy shallows;

text: Tiktaalik

text: with limb-like fins that could take it onto land;

text: stem-tetrapods

text: in weed-filled swamps, such as Acanthostega, which had eight-digited feet; and

text: Ichthyostega

text: , with full limbs. Their descendants also included pelagic lobe-finned fish such as

text: coelacanth

text: species.

text: In contrast to STD, the subtype spondylocostal dysostosis, or SCD features intrinsic rib anomalies, in addition to vertebral anomalies. Intrinsic rib anomalies include defects such as birfurcation, broadening and fusion that are not directly related to the vertebral anomalies (such as in STD, where extensive posterior rib fusion occurs due to segmentation defects and extreme shortening of the thoracic vertebral column). In both subtypes, the pulmonary restriction may result in pulmonary hypertension, and have other potential cardiac implications.

text: In contrast to

text: STD

text: , the subtype spondylocostal dysostosis, or SCD features intrinsic rib anomalies, in addition to vertebral anomalies. Intrinsic rib anomalies include defects such as birfurcation, broadening and fusion that are not directly related to the vertebral anomalies (such as in STD, where extensive posterior rib fusion occurs due to segmentation defects and extreme shortening of the thoracic vertebral column). In both subtypes, the pulmonary restriction may result in pulmonary hypertension, and have other potential cardiac implications.

text: Like all Plasmodium species P. robinsoni has both vertebrate and insect hosts. The vertebrate hosts for this parasite are lizards.

text: Like all Plasmodium species P. robinsoni has both

text: vertebrate

text: and

text: insect

text: lizard

text: s.

text: The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate, in which the notochord (a flexible rod of uniform composition) found in all chordates has been replaced by a segmented series of bones—vertebrae separated by intervertebral discs. The vertebral column houses the spinal canal, a cavity that encloses and protects the spinal cord.

text: The vertebral column, also known as the backbone or spine, is part of the

text: axial skeleton

text: . The vertebral column is the defining characteristic of a

text: vertebrate

text: , in which the

text: notochord

text: (a flexible rod of uniform composition) found in all

text: chordates

text: has been replaced by a segmented series of

text: bone

text: s—

text: vertebra

text: e separated by

text: intervertebral disc

text: s. The vertebral column houses the

text: spinal canal

text: , a cavity that encloses and protects the

text: spinal cord

text: Pharyngeal arches are characteristic features of vertebrates whose origin can be traced back through chordates to basal deuterostomes who also share endodermal outpocketings of the pharyngeal apparatus. Similar patterns of gene expression can be detected in the developing pharynx of amphioxus and hemichordates. However, the vertebrate pharynx is unique in that it gives rise to endoskeletal support through the contribution of neural crest cells.

text: Pharyngeal arches are characteristic features of vertebrates whose origin can be traced back through

text: chordates

text: to basal

text: deuterostomes

text: who also share endodermal outpocketings of the pharyngeal apparatus. Similar patterns of gene expression can be detected in the developing pharynx of

text: amphioxus

text: and

text: hemichordates

text: . However, the vertebrate pharynx is unique in that it gives rise to

text: endoskeletal

text: support through the contribution of

text: neural crest

text: cells.

text: The foot of the elephant possesses what is perhaps one of the most unusual distal cushions found in vertebrates.  The forefoot (manus) and hindfoot (pes) contain huge pads of fat that are scaled to cope with the massive loadings imposed by the largest terrestrial vertebrate.  In addition, a cartilage-like projection (prepollex in the forelimb and prehallux in the hind limb) appears to anchor the distal cushion to the bones of the elephant's foot.

text: The foot of the elephant possesses what is perhaps one of the most unusual distal cushions found in vertebrates.  The forefoot (manus) and hindfoot (pes) contain huge pads of fat that are scaled to cope with the massive loadings imposed by the largest terrestrial vertebrate.  In addition, a

text: cartilage

text: -like projection (

text: prepollex

text: in the forelimb and

text: prehallux

text: in the hind limb) appears to anchor the distal cushion to the bones of the elephant's foot.

text: The Vertebrate and Genome Annotation (VEGA) project is a biological database dedicated to assisting researchers in locating specific areas of the genome and annotating genes or regions of vertebrate genomes. The VEGA browser is based on Ensembl web code and infrastructure and provides a public curation of known vertebrate genes for the scientific community.  The VEGA website is updated frequently to maintain the most current information about vertebrate genomes and attempts to present consistently high-quality annotation of all its published vertebrate genomes or genome regions. VEGA was developed by the Wellcome Trust Sanger Institute and is in close association with other annotation databases, such as ZFIN (The Zebrafish Information Network), the Havana Group and GenBank. Manual annotation is currently more accurate at identifying splice variants, pseudogenes, polyadenylation features, non-coding regions and complex gene arrangements than automated methods.

text: The Vertebrate and Genome Annotation (VEGA) project is a

text: biological database

text: dedicated to assisting researchers in locating specific areas of the

text: genome

text: and annotating genes or regions of vertebrate genomes. The VEGA browser is based on

text: Ensembl

text: web code and infrastructure and provides a public curation of known vertebrate genes for the scientific community.  The VEGA website is updated frequently to maintain the most current information about vertebrate genomes and attempts to present consistently high-quality

text: annotation

text: of all its published vertebrate genomes or genome regions. VEGA was developed by the

text: Wellcome Trust Sanger Institute

text: and is in close association with other annotation databases, such as

text: ZFIN

text: (The Zebrafish Information Network), the Havana Group and

text: GenBank

text: . Manual annotation is currently more accurate at identifying splice variants,

text: pseudogenes

text: polyadenylation

text: features, non-coding regions and complex gene arrangements than automated methods.

text: The species consists mostly of hermaphrodites which are known to reproduce by self-fertilization, but males do exist, and strong genetic evidence indicates occasional outcrossing. They are also the only simultaneous hermaphroditic vertebrates, and the concentration of males to hermaphrodites can vary depending on the local requirement for genetic diversity (for example, if an increase in the local parasite population occurred, secondary male numbers might increase).

text: The species consists mostly of hermaphrodites which are known to reproduce by

text: self-fertilization

text: , but males do exist, and strong genetic evidence indicates occasional

text: outcrossing

text: . They are also the only

text: simultaneous hermaphroditic

text: vertebrates, and the concentration of males to hermaphrodites can vary depending on the local requirement for genetic diversity (for example, if an increase in the local parasite population occurred, secondary male numbers might increase).

text: There is a bewildering array of variation on the complex digenean life cycle, and plasticity in this trait is probably a key to the group's success. In general, the life cycles may have two, three, or four obligate (necessary) hosts, sometimes with transport or paratenic hosts in between. The three-host life cycle is probably the most common.  In almost all species, the first host in the life cycle is a mollusc. This has led to the inference that the ancestral digenean was a mollusc parasite and that vertebrate hosts were added subsequently.

text: There is a bewildering array of variation on the complex digenean life cycle, and plasticity in this trait is probably a key to the group's success. In general, the life cycles may have two, three, or four obligate (necessary) hosts, sometimes with transport or

text: paratenic

text: hosts in between. The three-host life cycle is probably the most common.  In almost all species, the first host in the life cycle is a

text: mollusc

text: . This has led to the inference that the ancestral digenean was a mollusc parasite and that vertebrate hosts were added subsequently.

text: Dr. Bonnan teaches a variety of anatomy-based and evolutionary biology courses at Stockton University covering diverse topics such as vertebrate embryology, comparative vertebrate anatomy, vertebrate evolution, systematics, dinosaurs, and general zoology.

text: Size, however, is not the only difference: there are also substantial differences in shape. The hindbrain and midbrain of mammals are generally similar to those of other vertebrates, but dramatic differences appear in the forebrain, which is greatly enlarged and also altered in structure. The cerebral cortex is the part of the brain that most strongly distinguishes mammals. In non-mammalian vertebrates, the surface of the cerebrum is lined with a comparatively simple three-layered structure called the pallium. In mammals, the pallium evolves into a complex six-layered structure called neocortex or isocortex. Several areas at the edge of the neocortex, including the hippocampus and amygdala, are also much more extensively developed in mammals than in other vertebrates.

text: Size, however, is not the only difference: there are also substantial differences in shape. The hindbrain and midbrain of mammals are generally similar to those of other vertebrates, but dramatic differences appear in the forebrain, which is greatly enlarged and also altered in structure. The cerebral cortex is the part of the brain that most strongly distinguishes mammals. In non-mammalian vertebrates, the surface of the

text: cerebrum

text: is lined with a comparatively simple three-layered structure called the

text: pallium

text: . In mammals, the pallium evolves into a complex six-layered structure called

text: neocortex

text: or isocortex. Several areas at the edge of the neocortex, including the hippocampus and

text: amygdala

text: , are also much more extensively developed in mammals than in other vertebrates.

text: Significant research has been conducted on the genes responsible for controlling circadian rhythm, in particular within the SCN. Knowledge of the gene expression of Clock (Clk) and Period2 (Per2), two of the many genes responsible for regulating circadian rhythm within the individual cells of the SCN, has allowed for a greater understanding of how genetic expression influences the regulation of circadian rhythm-controlled behaviors. Studies on thermoregulation of ruin lizards and mice have informed some connections between the neural and genetic components of both vertebrates when experiencing induced hypothermic conditions. Certain findings have reflected how evolution of SCN both structurally and genetically has resulted in the engagement of characteristic and stereotyped thermoregulatory behavior in both classes of vertebrates.

text: Significant research has been conducted on the genes responsible for controlling circadian rhythm, in particular within the SCN. Knowledge of the gene expression of Clock (Clk) and Period2 (Per2), two of the many genes responsible for regulating circadian rhythm within the individual cells of the SCN, has allowed for a greater understanding of how genetic expression influences the regulation of circadian rhythm-controlled behaviors. Studies on

text: thermoregulation

text: of

text: ruin lizard

text: s and mice have informed some connections between the neural and genetic components of both vertebrates when experiencing induced hypothermic conditions. Certain findings have reflected how evolution of SCN both structurally and genetically has resulted in the engagement of characteristic and stereotyped thermoregulatory behavior in both classes of vertebrates.

text: Knowledge of fish age characteristics is necessary for stock assessments, and to develop management or conservation plans. Size is generally associated with age; however, there are variations in size at any particular age for most fish species making it difficult to estimate one from the other with precision. Therefore, researchers interested in determining a fish age look for structures which increase incrementally with age. The most commonly used techniques involve counting natural growth rings on the scales, otoliths, vertebrate, fin spines, eye lenses, teeth, or bones of the jaw, pectoral girdle, and opercular series. Even reliable aging techniques may vary among species; often, several different bony structures are compared among a population in order to determine the most accurate method.

text: Knowledge of fish age characteristics is necessary for stock assessments, and to develop management or conservation plans. Size is generally associated with age; however, there are variations in size at any particular age for most fish species making it difficult to estimate one from the other with precision. Therefore, researchers interested in determining a fish age look for structures which increase incrementally with age. The most commonly used techniques involve counting natural growth rings on the

text: scales

text: otoliths

text: vertebrate

text: fin spines

text: eye lenses

text: , teeth, or

text: bones of the jaw

text: , pectoral girdle, and

text: opercular series

text: . Even reliable aging techniques may vary among species; often, several different bony structures are compared among a population in order to determine the most accurate method.

text: Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals.  Bone tissue is a type of dense connective tissue. Because bones come in a variety of shapes and have a complex internal and external structure they are lightweight, yet strong and hard, in addition to fulfilling their many other functions.

text: Bones are rigid

text: organs

text: that form part of the

text: endoskeleton

text: of

text: vertebrate

text: red

text: and

text: white blood cell

text: s and store

text: mineral

text: s.  Bone tissue is a type of dense

text: connective tissue

text: . Because bones come in a variety of shapes and have a complex internal and external

text: structure

text: they are lightweight, yet strong and hard, in addition to fulfilling their many other

text: functions

text: Additionally, an erect posture demands precise balance, the result of a rapidly functioning neuromuscular system. This suggests endothermic metabolism, because an ectothermic animal would be unable to walk or run, and thus to evade predators, when its core temperature was lowered. Other evidence for endothermy includes limb length (many dinosaurs possessed comparatively long limbs) and bipedalism, both found today only in endotherms. Many bipedal dinosaurs possessed gracile leg bones with a short thigh relative to calf length. This is generally an adaptation to frequent sustained running, characteristic of endotherms which, unlike ectotherms, are capable of producing sufficient energy to stave off the onset of anaerobic metabolism in the muscle.

text: Echinoderms are marine animals, widespread in all oceans, but not found in fresh water. Just below their skin is an endoskeleton composed of calcareous plates or ossicles.

text: Echinoderm

text: s are marine animals, widespread in all oceans, but not found in fresh water. Just below their skin is an

text: endoskeleton

text: composed of

text: calcareous

text: plates or

text: ossicle

text: s.

text: The carapace of the young is strongly keeled. The keels are tubercular posteriorly on the second and third vertebral shields. The posterior margin is strongly crenulated. The marginal serrature disappears in adolescent specimens and the vertebral keel, after being reduced to a series of low knobs, vanishes entirely in the full-grown, the carapace of which is very convex. The nuchal shield is small, trapezoidal and broadest posteriorly. The first vertebral is as broad or broader in front as behind. The second vertebral is longer than the third, with which it forms a straight transverse suture. The fourth is longest and forms a broad suture with the third. The second vertebral is broader than long in the young, and as long as broad in the adult. Plastron is angulate laterally in the young. The anterior and posterior lobes are rather narrow and shorter than the width of the bridge, truncate anteriorly and are openly notched posteriorly. The longest median suture is between the abdominals and the shortest is between the gulars, which equals about one half that between the humerals. The suture between gulars and humerals forms an obtuse angle, as does that between humerals and pectorals. The inguinal is large and the axillary is smaller.

text: The

text: carapace

text: of the young is strongly keeled. The

text: keel

text: s are tubercular posteriorly on the second and third vertebral shields. The posterior margin is strongly crenulated. The marginal serrature disappears in adolescent specimens and the vertebral keel, after being reduced to a series of low knobs, vanishes entirely in the full-grown, the carapace of which is very convex. The

text: nuchal

text: shield is small, trapezoidal and broadest posteriorly. The first

text: vertebral

text: is as broad or broader in front as behind. The second vertebral is longer than the third, with which it forms a straight transverse suture. The fourth is longest and forms a broad suture with the third. The second vertebral is broader than long in the young, and as long as broad in the adult.

text: Plastron

text: is angulate laterally in the young. The anterior and posterior lobes are rather narrow and shorter than the width of the bridge, truncate anteriorly and are openly notched posteriorly. The longest median

text: suture

text: is between the abdominals and the shortest is between the gulars, which equals about one half that between the humerals. The suture between gulars and humerals forms an

text: obtuse angle

text: , as does that between humerals and pectorals. The

text: inguinal

text: is large and the

text: axilla

text: ry is smaller.

text: Tetrapods, vertebrates with four limbs, evolved from other rhipidistian fish over a relatively short timespan during the Late Devonian (). The early groups are grouped together as Labyrinthodontia. They retained aquatic, fry-like tadpoles, a system still seen in modern amphibians.

text: Tetrapod

text: s, vertebrates with four limbs, evolved from other

text: rhipidistia

text: n fish over a relatively short timespan during the Late Devonian (). The early groups are grouped together as

text: Labyrinthodontia

text: . They retained aquatic, fry-like

text: tadpole

text: s, a system still seen in

text: modern amphibians

text: The vertebrae of lobe-finned fishes consist of three discrete bony elements. The vertebral arch surrounds the spinal cord, and is of broadly similar form to that found in most other vertebrates. Just beneath the arch lies a small plate-like pleurocentrum, which protects the upper surface of the notochord, and below that, a larger arch-shaped intercentrum to protect the lower border. Both of these structures are embedded within a single cylindrical mass of cartilage. A similar arrangement was found in primitive tetrapods, but, in the evolutionary line that led to reptiles (and hence, also to mammals and birds), the intercentrum became partially or wholly replaced by an enlarged pleurocentrum, which in turn became the bony vertebral body.

text: The vertebrae of

text: lobe-finned fishes

text: notochord

text: , and below that, a larger arch-shaped intercentrum to protect the lower border. Both of these structures are embedded within a single cylindrical mass of cartilage. A similar arrangement was found in primitive

text: tetrapod

text: s, but, in the evolutionary line that led to reptiles (and hence, also to mammals and birds), the intercentrum became partially or wholly replaced by an enlarged pleurocentrum, which in turn became the bony vertebral body.

text: One effect of ageing and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.  This general shrinking of disc size is partially responsible for the common decrease in height as humans age.  The anulus fibrosus also becomes weaker with age and has an increased risk of tearing.  In addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone. As the fissures are formed in the anulus fibrosis due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves. A herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.  Other degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae. This degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.

text: One effect of ageing and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.  This general shrinking of disc size is partially responsible for the common decrease in height as humans age.  The anulus fibrosus also becomes weaker with age and has an increased risk of tearing.  In addition, the cartilage endplates begin thinning, fissures begin to form, and there is

text: sclerosis

text: of the

text: subchondral bone

text: . As the fissures are formed in the anulus fibrosis due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves. A herniated disc can cause mild to severe pain such as

text: sciatica

text: and treatment for herniated discs range from physical therapy to surgery.  Other degeneration of the vertebral column includes

text: diffuse idiopathic skeletal hyperostosis

text: (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae. This degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.

text: The 2R hypothesis or Ohno's hypothesis, first proposed by Susumu Ohno in 1970, is a hypothesis in genomics and molecular evolution suggesting that the genomes of the early vertebrate lineage underwent two complete genome duplications, and thus modern vertebrate genomes reflect paleopolyploidy.  The name derives from the 2 rounds of duplication originally hypothesized by Ohno, but refined in a 1994 version, and the term 2R hypothesis was probably coined in 1999. Variations in the number and timings of genome duplications typically still are referred to as examples of the 2R hypothesis. The 2R hypothesis has been the subject of much research and controversy; however, with growing support from genome data, including the human genome, the balance of opinion has shifted strongly in favour of support for the hypothesis. According to Hokamp et al. (2003), the version of the genome duplication hypothesis from which 2R hypothesis takes its name appears in Holland et al. (1994) and the term was coined in Hughes (1999).

text: The 2R hypothesis or Ohno's hypothesis, first proposed by

text: Susumu Ohno

text: in 1970, is a hypothesis in

text: genomics

text: and

text: molecular evolution

text: suggesting that the genomes of the early

text: vertebrate

text: lineage underwent two complete

text: genome duplication

text: s, and thus modern vertebrate genomes reflect

text: paleopolyploidy

text: .  The name derives from the 2 rounds of duplication originally hypothesized by Ohno, but refined in a 1994 version, and the term 2R hypothesis was probably coined in 1999. Variations in the number and timings of genome duplications typically still are referred to as examples of the 2R hypothesis. The 2R hypothesis has been the subject of much research and controversy; however, with growing support from genome data, including the

text: human genome

text: , the balance of opinion has shifted strongly in favour of support for the hypothesis. According to Hokamp et al. (2003), the version of the genome duplication hypothesis from which 2R hypothesis takes its name appears in Holland et al. (1994) and the term was coined in Hughes (1999).

text: Fish do not have necks, so the head is directly connected to the shoulders. In contrast, land animals use necks to move their heads so they can look down to see the food on the ground. The greater the mobility of the neck, the more visibility the land animal has. As lineages moved from completely aquatic environments to shallower waters and land, they gradually evolved vertebral columns that increased neck mobility. The first neck vertebra that evolved permitted the animals to have flexion and extension of the head so that they can see up and down. The second neck vertebra evolved to allow rotation of the neck for moving the head left and right. As tetrapod species continued to evolve on land, adaptations included seven or more vertebrae, allowing increasing neck mobility.

text: During his re-examination of the Burgess Shale fauna in 1979, paleontologist Simon Conway Morris placed P. gracilens among the chordates, making it perhaps the oldest known ancestor of modern vertebrates. He did this because it seemed to have a very primitive, proto-notochord, however, the status of Pikaia as a chordate is not universally accepted; its preservational mode suggests that it had cuticle, which is uncharacteristic of the vertebrates  (although characteristic of other cephalochordates); further, its tentacles are unknown from other vertebrate lineages. The presence of earlier chordates among the Chengjiang, including Haikouichthys and Myllokunmingia, appears to show that cuticle is not necessary for preservation, overruling the taphonomic argument, but the presence of tentacles remains intriguing, and the organism cannot be assigned conclusively, even to the vertebrate stem group. Its anatomy closely resembles the modern creature Branchiostoma.

text: During his re-examination of the Burgess Shale fauna in 1979,

text: paleontologist

text: Simon Conway Morris

text: placed P. gracilens among the

text: chordate

text: s, making it perhaps the oldest known ancestor of modern

text: vertebrate

text: s. He did this because it seemed to have a very primitive, proto-

text: notochord

text: , however, the status of Pikaia as a chordate is not universally accepted; its preservational mode suggests that it had

text: cuticle

text: , which is uncharacteristic of the vertebrates  (although characteristic of other

text: cephalochordate

text: s); further, its tentacles are unknown from other vertebrate lineages. The presence of earlier chordates among the

text: Chengjiang

text: , including

text: Haikouichthys

text: and

text: Myllokunmingia

text: , appears to show that cuticle is not necessary for preservation, overruling the taphonomic argument, but the presence of tentacles remains intriguing, and the organism cannot be assigned conclusively, even to the vertebrate

text: stem group

text: . Its anatomy closely resembles the modern creature

text: Branchiostoma

text: Unicellular eukaryotes usually reproduce asexually by mitosis under favorable conditions.  However, under stressful conditions such as nutrient limitations and other conditions associated with DNA damage, they tend to reproduce sexually by meiosis and syngamy.

text: Unicellular eukaryotes usually reproduce asexually by

text: mitosis

text: under favorable conditions.  However, under stressful conditions such as nutrient limitations and other conditions associated with DNA damage, they tend to reproduce sexually by

text: meiosis

text: and

text: syngamy

text: Some regarded Polypterus as a living fossil, part of the missing link between fishes and amphibians, helping to show how fish fins had evolved to become paired limbs.

text: The first major groups of amphibians developed in the Devonian period, around 370 million years ago, from lobe-finned fish which were similar to the modern coelacanth and lungfish. These ancient lobe-finned fish had evolved multi-jointed leg-like fins with digits that enabled them to crawl along the sea bottom. Some fish had developed primitive lungs to help them breathe air when the stagnant pools of the Devonian swamps were low in oxygen. They could also use their strong fins to hoist themselves out of the water and onto dry land if circumstances so required. Eventually, their bony fins would evolve into limbs and they would become the ancestors to all tetrapods, including modern amphibians, reptiles, birds, and mammals. Despite being able to crawl on land, many of these prehistoric tetrapodomorph fish still spent most of their time in the water. They had started to develop lungs, but still breathed predominantly with gills.

text: The first major groups of amphibians developed in the

text: Devonian

text: period, around 370 million years ago, from

text: lobe-finned fish

text: which were similar to the modern

text: coelacanth

text: and

text: lungfish

text: . These ancient lobe-finned fish had evolved multi-jointed leg-like fins with digits that enabled them to crawl along the sea bottom. Some fish had developed primitive lungs to help them breathe air when the stagnant pools of the Devonian swamps were low in oxygen. They could also use their strong fins to hoist themselves out of the water and onto dry land if circumstances so required. Eventually, their bony fins would

text: evolve

text: into limbs and they would become the ancestors to all

text: tetrapod

text: s, including modern amphibians, reptiles, birds, and

text: mammal

text: s. Despite being able to crawl on land, many of these prehistoric

text: tetrapodomorph

text: fish still spent most of their time in the water. They had started to develop lungs, but still breathed predominantly with gills.

text: The Nile tilapia has recently been discovered in a small stream in central Arkansas. This invasive species may harm the other aquatic life present in this stream within the next few years, depending on how quickly it is able to reproduce and how adapted it is to competition with other aquatic vertebrates. Evidence supports the possibility that the Nile tilapia has established a strong breeding ground and will eventually endanger other fish species, possibly competitively exclude them.

text: Like all Plasmodium species P. vaughani has both vertebrate and insect hosts. The vertebrate hosts for this parasite are birds.

text: Like all Plasmodium species P. vaughani has both

text: vertebrate

text: and

text: insect

text: bird

text: s.

text: P. canadensis coexisted with ankylosaurids Anodontosaurus lambei, Edmontonia longiceps, Euoplocephalus tutus, the maniraptorans Atrociraptor marshalli, Epichirostenotes curriei, Richardoestesia gilmorei, Richardoestesia isosceles, the troodontid Paronychodon lacustris and an unnamed species of Troodon, the alvarezsaurid theropod Albertonykus borealis, the ornithomimids Dromiceiomimus brevitertius, Ornithomimus edmontonicus,  and an unnamed species of Struthiomimus, the bone-head pachycephalosaurids Stegoceras, and Sphaerotholus edmontonensis, the ornithopod Parksosaurus warreni, the hadrosaurids Edmontosaurus regalis, Hypacrosaurus altispinus, and Saurolophus osborni,  the ceratopsians Anchiceratops ornatus, Arrhinoceratops brachyops, Eotriceratops xerinsularis, Montanoceratops cerorhynchus, and the   tyrannosaurids Albertosaurus, Gorgosaurus and Daspletosaurus, which were the apex predators of this paleoenvironment. Of these, the hadrosaurs dominated in terms of sheer number and made up half of all dinosaurs who lived in this region. Vertebrates present in the Horseshoe Canyon Formation at the time of Pachyrhinosaurus included reptiles, and amphibians. Sharks, rays, sturgeons, bowfins, gars and the gar-like Aspidorhynchus made up the fish fauna. Reptiles such as turtles and crocodilians are rare in the Horseshoe Canyon Formation, and this was thought to reflect the relatively cool climate which prevailed at the time. A study by Quinney et al. (2013) however, showed that the decline in turtle diversity, which was previously attributed to climate, coincided instead with changes in soil drainage conditions, and was limited by aridity, landscape instability, and migratory barriers.   The saltwater plesiosaur Leurospondylus was present and freshwater environments were populated by turtles, Champsosaurus, and crocodilians like Leidyosuchus and Stangerochampsa. 	Evidence has shown that multituberculates and the early marsupial Didelphodon coyi were present.  Vertebrate trace fossils from this region included the tracks of theropods, ceratopsians and ornithopods, which provide evidence that these animals were also present.  Non-vertebrates in this ecosystem included both marine and terrestrial invertebrates.

text: P. canadensis coexisted with

text: ankylosaurids

text: Anodontosaurus

text: lambei,

text: Edmontonia

text: longiceps,

text: Euoplocephalus

text: tutus, the

text: maniraptoran

text: s

text: Atrociraptor

text: marshalli,

text: Epichirostenotes

text: curriei,

text: Richardoestesia

text: gilmorei,

text: Richardoestesia

text: isosceles, the

text: troodontid

text: Paronychodon

text: lacustris and an unnamed species of

text: Troodon

text: , the

text: alvarezsaurid

text: theropod

text: Albertonykus

text: borealis, the

text: ornithomimids

text: Dromiceiomimus

text: brevitertius,

text: Ornithomimus

text: edmontonicus,  and an unnamed species of

text: Struthiomimus

text: , the

text: bone-head pachycephalosaurids

text: Stegoceras

text: , and

text: Sphaerotholus

text: edmontonensis, the

text: ornithopod

text: Parksosaurus

text: warreni, the

text: hadrosaurids

text: Edmontosaurus

text: regalis,

text: Hypacrosaurus

text: altispinus, and

text: Saurolophus

text: osborni,  the

text: ceratopsians

text: Anchiceratops

text: ornatus,

text: Arrhinoceratops

text: brachyops,

text: Eotriceratops

text: xerinsularis,

text: Montanoceratops

text: cerorhynchus, and the

text: tyrannosaurids

text: Albertosaurus

text: Gorgosaurus

text: and

text: Daspletosaurus

text: , which were the

text: apex predators

text: of this paleoenvironment. Of these, the hadrosaurs dominated in terms of sheer number and made up half of all dinosaurs who lived in this region. Vertebrates present in the Horseshoe Canyon Formation at the time of Pachyrhinosaurus included

text: reptile

text: s, and

text: amphibian

text: s.

text: Shark

text: s,

text: rays

text: sturgeon

text: s,

text: bowfin

text: s,

text: gar

text: s and the gar-like

text: Aspidorhynchus

text: made up the fish fauna. Reptiles such as turtles and crocodilians are rare in the Horseshoe Canyon Formation, and this was thought to reflect the relatively cool climate which prevailed at the time. A study by Quinney et al. (2013) however, showed that the decline in turtle diversity, which was previously attributed to climate, coincided instead with changes in soil drainage conditions, and was limited by aridity, landscape instability, and migratory barriers.   The saltwater

text: plesiosaur

text: Leurospondylus

text: turtle

text: s,

text: Champsosaurus

text: , and

text: crocodilia

text: ns like

text: Leidyosuchus

text: and

text: Stangerochampsa

text: . 	Evidence has shown that

text: multituberculate

text: s and the early

text: marsupial

text: Didelphodon

text: theropods

text: ceratopsians

text: and

text: ornithopods

text: invertebrate

text: s.

text: Throughout the Permian period, the synapsids included the dominant carnivores and several important herbivores. In the subsequent Triassic period, however, a previously obscure group of sauropsids, the archosaurs, became the dominant vertebrates. The mammaliaforms appeared during this period; their superior sense of smell, backed up by a large brain, facilitated entry into nocturnal niches with less exposure to archosaur predation. The nocturnal lifestyle may have contributed greatly to the development of mammalian traits such as endothermy and hair. Later in the Mesozoic, after theropod dinosaurs replaced rauisuchians as the dominant carnivores, mammals spread into other ecological niches. For example, some became aquatic, some were gliders, and some even fed on juvenile dinosaurs.

text: Throughout the

text: Permian

text: period, the synapsids included the dominant

text: carnivore

text: s and several important

text: herbivore

text: s. In the subsequent Triassic period, however, a previously obscure group of sauropsids, the

text: archosaur

text: s, became the dominant vertebrates. The

text: mammaliaforms

text: appeared during this period; their superior sense of smell, backed up by a large brain, facilitated entry into nocturnal niches with less exposure to archosaur predation. The nocturnal lifestyle may have contributed greatly to the development of mammalian traits such as

text: endothermy

text: and

text: hair

text: . Later in the

text: Mesozoic

text: , after

text: theropod dinosaurs

text: replaced

text: rauisuchia

text: ns as the dominant carnivores, mammals spread into other

text: ecological niche

text: s. For example, some became

text: aquatic

text: , some were

text: gliders

text: , and some even

text: fed on juvenile dinosaurs

text: Evolutionary origins of vertebrates as well as the phylum Chordata have not been scientifically determined. Many believe vertebrates diverged from a common ancestor of chordates and echinoderms. This belief is well supported by the prehistoric marine creature Amphioxus. Amphioxus does not possess bone, making it an invertebrate, but it has common features with vertebrates including a segmented body and a notochord. This could imply that Amphioxus is a transitional form between an early chordate, echinoderm or common ancestor, and vertebrates.

text: In 747, a Buddhist saint, Padmasambhava (known in Bhutan as Guru Rimpoche and sometimes referred to as the Second Buddha), came to Bhutan from India at the invitation of one of the numerous local kings. After reportedly subduing eight classes of demons and converting the king, Guru Rimpoche moved on to Tibet. Upon his return from Tibet, he oversaw the construction of new monasteries in the Paro Valley and set up his headquarters in Bumthang. According to tradition, he founded the Nyingmapa sect—also known as the "old sect" or Red Hat sect—of Mahayana Buddhism, which became for a time the dominant religion of Bhutan. Guru Rimpoche plays a great historical and religious role as the national patron saint who revealed the tantras—manuals describing forms of devotion to natural energy—to Bhutan. Following the guru's sojourn, Indian influence played a temporary role until increasing Tibetan migrations brought new cultural and religious contributions.

text: In 747, a Buddhist saint,

text: Padmasambhava

text: (known in Bhutan as

text: Guru Rimpoche

text: and sometimes referred to as the Second Buddha), came to Bhutan from India at the invitation of one of the numerous local kings. After reportedly subduing eight classes of demons and converting the king, Guru Rimpoche moved on to Tibet. Upon his return from Tibet, he oversaw the construction of new monasteries in the Paro Valley and set up his headquarters in

text: Bumthang

text: . According to tradition, he founded the

text: Nyingmapa

text: sect—also known as the "old sect" or Red Hat sect—of

text: Mahayana Buddhism

text: , which became for a time the dominant religion of Bhutan. Guru Rimpoche plays a great historical and religious role as the national patron saint who revealed the

text: tantra

text: s—manuals describing forms of devotion to natural energy—to Bhutan. Following the guru's sojourn, Indian influence played a temporary role until increasing Tibetan migrations brought new cultural and religious contributions.

text: Like all Plasmodium species P. pessoai has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. pessoai has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: The vertebral column already shows many traits that are typical for later sauropods which allowed them to attain great body sizes, although in later sauropods these traits are much more developed. The centra and neural spines show early hints of hollowing as a weight-saving measure. The dorsal vertebrae are stabilized with hyposphene-hypantrum articulations, accessory projections that link the vertebrae with each other. The sacrum is strengthened through an additional fourth sacral vertebra.

text: The vertebral column already shows many traits that are typical for later sauropods which allowed them to attain great body sizes, although in later sauropods these traits are much more developed. The centra and neural spines show early hints of hollowing as a weight-saving measure. The dorsal vertebrae are stabilized with

text: hyposphene-hypantrum articulation

text: s, accessory projections that link the vertebrae with each other. The sacrum is strengthened through an additional fourth sacral vertebra.

text: Cervical vertebrae possess transverse foramina to allow for the vertebral arteries to pass through on their way to the foramen magnum to end in the circle of Willis.  These are the smallest, lightest vertebrae and the vertebral foramina are triangular in shape.  The spinous processes are short and often bifurcated (the spinous process of C7, however, is not bifurcated, and is substantially longer than that of the other cervical spinous processes).

text: Cervical vertebrae possess transverse foramina to allow for the vertebral arteries to pass through on their way to the

text: foramen magnum

text: to end in the

text: circle of Willis

text: .  These are the smallest, lightest vertebrae and the vertebral foramina are triangular in shape.  The spinous processes are short and often

text: bifurcated

text: (the spinous process of C7, however, is not bifurcated, and is substantially longer than that of the other cervical spinous processes).

text: Ghote suspects that the murderer may be an employee at the nearby hospital. He enlists the inspector originally assigned to Chagoo's death to test this theory.

text: Therefore, defining the mechanisms of neural crest development may reveal key insights into vertebrate evolution and neurocristopathies.

text: After On the Origin of Species, the idea of "lower animals" representing earlier stages in evolution lingered, as demonstrated in Ernst Haeckel's figure of the human pedigree. While the vertebrates were then seen as forming a sort of evolutionary sequence, the various classes were distinct, the undiscovered intermediate forms being called "missing links."

text: After On the Origin of Species, the idea of "lower animals" representing earlier stages in evolution lingered, as demonstrated in

text: Ernst Haeckel

text: 's figure of the human pedigree. While the vertebrates were then seen as forming a sort of evolutionary sequence, the various

text: classes

text: were distinct, the undiscovered intermediate forms being called "missing links."

text: The vertebrates are the only chordate group to exhibit cephalisation, the concentration of brain functions in the head. A slight swelling of the anterior end of the nerve cord is found in the lancelet, though it lacks the eyes and other complex sense organs comparable to those of vertebrates. Other chordates do not show any trends towards cephalisation.

text: The vertebrates are the only

text: chordate

text: group to exhibit

text: cephalisation

text: , the concentration of

text: brain

text: functions in the head. A slight swelling of the anterior end of the nerve cord is found in the

text: lancelet

text: , though it lacks the eyes and other complex sense

text: organs

text: comparable to those of vertebrates. Other chordates do not show any trends towards cephalisation.

text: The ascending lumbar vein is a vein that runs up through the lumbar region on the side of the vertebral column.

text: The ascending lumbar vein is a vein that runs up through the lumbar region on the side of the

text: vertebral column

text: Other gardens in Valencia include:

text: Other gardens in Valencia include:

text: These different types of diversity may not be independent. There is, for example, a close link between vertebrate taxonomic and ecological diversity.

text: In the CDP the population was spread out with 42.9% under the age of 18, 13.2% from 18 to 24, 21.8% from 25 to 44, 16.8% from 45 to 64, and 5.3% who were 65 years of age or older. The median age was 21 years. For every 100 females there were 97.6 males. For every 100 females age 18 and over, there were 85.0 males.

text: As in most vertebrates, fish jaws are bony or cartilaginous and oppose vertically, comprising an upper jaw and a lower jaw. The jaw is derived from the most anterior two pharyngeal arches supporting the gills, and usually bears numerous teeth. The skull of the last common ancestor of today's jawed vertebrates is assumed to have resembled sharks.

text: As in most

text: vertebrate

text: s, fish jaws are

text: bony

text: or

text: cartilaginous

text: and oppose vertically, comprising an upper jaw and a lower jaw. The jaw is derived from the most anterior two

text: pharyngeal arch

text: es supporting the gills, and usually bears numerous

text: teeth

text: . The skull of the last common ancestor of today's jawed vertebrates is assumed to have resembled sharks.

text: Like all Plasmodium species P. mexicanum has both vertebrate and insect hosts. The vertebrate hosts for this parasite are reptiles.

text: Like all Plasmodium species P. mexicanum has both

text: vertebrate

text: and

text: insect

text: reptile

text: s.

text: According to Khafi Khan, three to four thousand of his men were killed. Binod Singh is believed to have lost his life in this massacre, too. That was in 1716.

text: The describing authors established several unique derived traits, autapomorphies. The cervical vertebra has a lamina, bone sheet, between the front joint process, the prezygapophysis, and a rear process, the epipophysis, the edge of which lamina is markedly convex, the convex part being longer than the vertebral body and separated from both the prezygapophysis and the epipophysis by conspicuous notches. With the first and second dorsal vertebrae, the prezygapophysis and the lamina between it and the vertebral body are arranged on a vertical line, the joint facet of the prezygapophysis and the front vertebral body face being positioned in the same plane. With the second dorsal vertebra, the joint facets of the rear joint processes, the postzygapophyses, are strongly concave. From at least the sixth dorsal vertebra onwards, the fossa or hollowed out area, below the prezygapophysis is divided into two smaller depressions.

text: The describing authors established several unique derived traits,

text: autapomorphies

text: . The cervical vertebra has a

text: lamina

text: , bone sheet, between the front joint process, the

text: prezygapophysis

text: , and a rear process, the

text: epipophysis

text: , the edge of which lamina is markedly convex, the convex part being longer than the vertebral body and separated from both the prezygapophysis and the epipophysis by conspicuous notches. With the first and second dorsal vertebrae, the prezygapophysis and the lamina between it and the vertebral body are arranged on a vertical line, the joint facet of the prezygapophysis and the front vertebral body face being positioned in the same plane. With the second dorsal vertebra, the joint facets of the rear joint processes, the

text: postzygapophyses

text: , are strongly concave. From at least the sixth dorsal vertebra onwards, the fossa or hollowed out area, below the prezygapophysis is divided into two smaller depressions.

text: 1926 -Introduction of Radio Technology programme

text: The Life of Vertebrates is a noted biology textbook by John Zachary Young.

text: The Life of Vertebrates is a noted biology textbook by

text: John Zachary Young

text: Genetic genealogy has identified a specific location of a gene on a chromosome for Klippel-Feil Syndrome.  Mutations in the GDF6 and GDF3 genes have also been identified to cause the disease, although some people with Klippel–Feil syndrome do not have identified mutations in the GDF6 or GDF3 genes. In this case, the cause of the condition in these individuals is unknown. GDF6 and GDF3 genes provide the body with instructions for making proteins involved in regulating the growth and maturation of bone and cartilage. These proteins actively regulate cell growth in embryonic and adult tissue. GDF6 specifically is involved in the formation of vertebral bones, among others, and establishing boundaries between bones in skeletal development while GDF3 is involved with bone and cartilage growth. Mutations cause reductions in these functional proteins but, it is unclear exactly how a shortage in these proteins leads to incomplete separation of the vertebrae in people with Klippel–Feil syndrome.  However, when the GDF6 gene was knocked out in mice, the result was the fusion of bones.  Only by identifying the link between the genetic etiology and the phenotypic pathoanatomy of Klippel–Feil syndrome will we be able to rationalize the heterogeneity of the syndrome.

text: Genetic genealogy

text: has identified a specific location of a gene on a

text: chromosome

text: for Klippel-Feil Syndrome.  Mutations in the

text: and

text: genes have also been identified to cause the disease, although some people with Klippel–Feil syndrome do not have identified mutations in the GDF6 or GDF3 genes. In this case, the cause of the condition in these individuals is unknown. GDF6 and GDF3 genes provide the body with instructions for making proteins involved in regulating the growth and maturation of bone and cartilage. These proteins actively regulate cell growth in

text: embryonic

text: and adult tissue. GDF6 specifically is involved in the formation of vertebral bones, among others, and establishing boundaries between bones in skeletal development while GDF3 is involved with bone and cartilage growth.

text: Mutations

text: cause reductions in these functional proteins but, it is unclear exactly how a shortage in these proteins leads to incomplete separation of the vertebrae in people with Klippel–Feil syndrome.  However, when the GDF6 gene was knocked out in mice, the result was the fusion of bones.  Only by identifying the link between the genetic etiology and the phenotypic pathoanatomy of Klippel–Feil syndrome will we be able to rationalize the heterogeneity of the syndrome.

text: Consideration as to whether an animal (more specifically a vertebrate) uses internal or external fertilisation is often dependent on the method of birth. Oviparous animals laying eggs with thick calcium shells, such as chickens, or thick leathery shells generally reproduce via internal fertilisation so that the sperm fertilises the egg without having to pass through the thick, protective, tertiary layer of the egg. Ovoviviparous and viviparous animals also use internal fertilisation. It is important to note that although some organisms reproduce via amplexus, they may still use internal fertilisation, as with some salamanders. Advantages to internal fertilisation include: minimal waste of gametes; greater chance of individual egg fertilisation, relatively "longer" time period of egg protection, and selective fertilisation; many females have the ability to store sperm for extended periods of time and can fertilise their eggs at their own desire.

text: Consideration as to whether an animal (more specifically a vertebrate) uses

text: internal

text: or

text: external fertilisation

text: is often dependent on the method of birth. Oviparous animals laying eggs with thick calcium shells, such as

text: chickens

text: , or thick leathery shells generally reproduce via internal fertilisation so that the sperm fertilises the egg without having to pass through the thick, protective, tertiary layer of the egg.

text: Ovoviviparous

text: and

text: viviparous

text: animals also use internal fertilisation. It is important to note that although some organisms reproduce via

text: amplexus

text: , they may still use internal fertilisation, as with some salamanders. Advantages to internal fertilisation include: minimal waste of gametes; greater chance of individual egg fertilisation, relatively "longer" time period of egg protection, and selective fertilisation; many females have the ability to store sperm for extended periods of time and can fertilise their eggs at their own desire.