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Gastralia (singular gastralium) are dermal bones found in the ventral body wall of crocodilian and ''Sphenodon'' species. They are found between the sternum and pelvis, and do not articulate with the vertebrae. In modern animals, they provide support for the abdomen and attachment sites for abdominal muscles. These bones may have been derived from the ventral scales found in animals like rhipidistians, labyrinthodonts, and ''Acanthostega'', and may be related to ventral elements of turtle plastrons. Similar but not homologous cartilagenous elements are found in the ventral body walls of lizards and anurans. The terminology for these groups of structures is confused; both types, along with sternal ribs (ossified costal cartilages), 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 dinosaurs, pterosaurs, plesiosaurs, champsosaurs and some primitive pelycosaurs. In dinosaurs, the elements articulate with each other in a sort of zig-zag along the midline and may have aided in respiration.〔 Although they were thought to be present in some basal ornithischian dinosaurs, and sauropods (most notably ''Eobrontosaurus''), 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 scapula and fibula of an ''Allosaurus fragilis'' specimen catalogued as USNM 4734 are both pathological, both probably due to healed fractures.〔Molnar, R. E., 2001, Theropod paleopathology: a literature survey: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 337-363.〕 The holotype 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 (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.〔 ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gastralium」の詳細全文を読む スポンサード リンク
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