Crocodiles have the abdominal ribs modified into gastraliaTyrannosaurus gastralia
Gastralia (sg.: gastralium) are dermal bones found in the ventral body wall of modern crocodilians and tuatara, and many prehistoric tetrapods. They are found between the sternum and pelvis, and do not articulate with the vertebrae. In these reptiles, gastralia provide support for the abdomen and attachment sites for abdominal muscles.
The possession of gastralia may be ancestral for Tetrapoda and were possibly derived from the ventral scales found in animals like
Discoveries about how the gastralia fit together in the skeleton of Sue the T. rex have led to an understanding that Tyrannosaurus bodies were more barrel-chested – and heavier – than previously thought.[5]
Pathology
The
USNM 4734 are both pathological, both probably due to healed fractures.[8]
The holotype of
pseudoarthrotic gastralia and a deviation to the right of the third and fourth neural spines of the neck vertebrae.[8]
An immature
dromaeosaurid specimen (which had not been described in the scientific literature as of 2001) from Tugrugeen Shireh was observed to have a "bifurcated" gastralium.[8]
^ abcdeMolnar RE (2001). "Theropod paleopathology: a literature survey". In Tanke DH, Carpenter K (eds.). Mesozoic Vertebrate Life. Indiana University Press. pp. 337–363.
