New Insights Into the Biology of Theropod Dinosaurs
AN ABSTRACT OF THE DISSERTATION OF Devon E. Quick for the degree of Doctor of Philosophy in Zoology presented on December 1, 2008. Title: New Insights into the Biology of Theropod Dinosaurs. Abstract approved: __________________________________________________________ John A. Ruben There is little, if any, direct fossil evidence of the cardiovascular, respiratory, reproductive or digestive biology of dinosaurs. However, a variety of data can be used to draw reasonable inferences about the physiology of the carnivorous theropod dinosaurs (Archosauria: Theropoda). Extant archosaurs, birds and crocodilians, possess regionally differentiated, vascularized and avascular lungs, although the crocodilian lung is less specialized than the avian lung air-sac system. Essential components of avian lungs include the voluminous, thin-walled abdominal air-sacs which are ventilated by an expansive sternum and specialized ribs. Inhalatory, paradoxical collapse of these air-sacs in birds is prevented by the synsacrum, pubes and femoral-thigh complex. The present work examines the theropod abdomen and reveals that it lacked sufficient space to have housed similarly enlarged abdominal air-sacs as well as the skeleto-muscular modifications requisite to have ventilated them. There is little evidence to indicate that theropod dinosaurs possessed a specialized bird-like, air-sac lung and, by extension, that theropod cardiovascular function was any more sophisticated than that of crocodilians. Conventional wisdom holds that theropod visceral anatomy was similar to that in birds. However, exceptional soft tissue preservation in Scipionyx samnitcus (Theropoda) offers rare evidence of in situ theropod visceral anatomy. Using computed tomography, close comparison of Scipionyx with gastrointestinal morphology in crocodilians, birds and lizards indicates that theropod visceral structure and “geography” was strikingly similar only to that in Alligator.
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