Gastralium
Encyclopedia
Dermal bone
A dermal bone - bony structures derived from intramembranous ossification that form components of the vertebrate skeleton including the skull, jaws, gills, fins and exoskeleton. In contrast to endochondral bone, dermal bone does not form from cartilage first and then calcify...
s found in the ventral
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
body wall of crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
n and Sphenodon
Tuatara
The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia. The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago. Their most recent common...
species. They are found between the sternum
Sternum
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...
and pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
, and do not articulate with the vertebrae. In modern animals, they provide support for the abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
and attachment sites for abdominal muscles.
These bones may have been derived from the ventral scales found in animals like rhipidistia
Rhipidistia
The Rhipidistia were lobe-finned fishes that are the ancestors of the tetrapods. Taxonomists traditionally considered the Rhipidistia a subgroup of Crossopterygii that described a group of fish that lived during the Devonian consisting of the Porolepiformes and Osteolepiformes...
ns, labyrinthodonts
Labyrinthodontia
Labyrinthodontia is an older term for any member of the extinct subclass of amphibians, which constituted some of the dominant animals of Late Paleozoic and Early Mesozoic times . The group is ancestral to all extant landliving vertebrates, and as such constitutes an evolutionary grade rather...
, and Acanthostega
Acanthostega
Acanthostega is an extinct labyrinthodont genus, among the first vertebrate animals to have recognizable limbs. It appeared in the Upper Devonian about 365 million years ago, and was anatomically intermediate between lobe-finned fishes and the first tetrapods fully capable of coming onto...
, and may be related to ventral elements of turtle
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
plastrons. Similar but not homologous
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
cartilagenous
Cartilage
Cartilage is a flexible 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...
elements are found in the ventral body walls of lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s and anurans. The terminology for these groups of structures is confused; both types, along with sternal ribs (ossified costal cartilages
Costal cartilages
The costal cartilages are bars of hyaline cartilage which serve to prolong the ribs forward and contribute very materially to the elasticity of the walls of the thorax.-Differences from 1-12:...
), have been called abdominal ribs, a term which should be avoided.
Gastralia are also present in a variety of extinct animals, including theropod and prosauropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s, pterosaur
Pterosaur
Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
s, plesiosaur
Plesiosaur
Plesiosauroidea is an extinct clade of carnivorous plesiosaur marine reptiles. Plesiosauroids, are known from the Jurassic and Cretaceous Periods...
s, and champsosaurs. In dinosaurs, the elements articulate with each other in a sort of zig-zag along the midline and may have aided in respiration
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
. Although they were thought to be present in some basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
ornithischia
Ornithischia
Ornithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
n dinosaurs, and sauropods (most notably Eobrontosaurus
Eobrontosaurus
Eobrontosaurus is the name given to a genus of dinosaur from the Late Jurassic of North America. It was a sauropod probably closely related to Apatosaurus. It is known from a single site from the lower Morrison Formation, dating to about 154 million years ago. It grew up to long.The type species, E...
), the perceived occurrences have been shown to be mistaken.
Pathology
The Allosaurus fragilis specimen USNM 8367 contained several gastralia which preserve evidence of healed fractures near their middle. Some of the fractures were poorly healed and "formed pseudoarthroses." An apparent subadult male Allosaurus fragilis was reported by Laws to have extensive pathologies. The possible subadult male A. fragilis specimen MOR 693 also had pathological gastralia. The left scapulaScapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
and fibula of an Allosaurus fragilis specimen catalogued as USNM 4734 are both pathological, both probably due to healed fractures.
The holoteype of Neovenator salerii had many pathologies, including pseudoarthrotic gastralia and a deviation to the right of the third and fourth neural spines of the neck vertebrae.
An immature dromaeosaurid specimen (which hadn't been described in the scientific literature as of 2001) from Tugrugeen Shireh was observed to have a "bifurcated" gastralium.
In the Gorgosaurus libratus holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
(NMC 2120) the 13th and 14th gastralia have healed fractures. Another G. libratus specimen catalogued as TMP94.12.602 bears multiple pathologies, including a pseudoarthortic gastralium.
The unidentified tyrannosaurid specimen TMP97.12.229 had a fractured and healed gastralium.