|Abstract or Summary
- Dinosaurs represent one of the most successful evolutionary radiations of terrestrial vertebrates, with a myriad of forms that dominated the terrestrial environment for over 180 million years. Despite the fact that dinosaurs are the focus of extensive popular and scholarly investigation, relatively little is actually known of their biology. The most reliable interpretations of the paleobiology of the dinosaurs, as well as other extinct taxa, depend on a synthetic approach that employs the uniformitarian principles of comparative and functional morphology, physiology, and embryology. This thesis is an attempt to apply such a multifaceted, interdisciplinary strategy to a broad range of biological questions about the dinosaurs, including aspects of behavior, phylogeny, and metabolic status. Specifically, the phylogenetic interpretations and biological reconstructions of dinosaurs in this study are based largely upon detailed examination of extant forms, in particular, their two closest relatives, crocodilians and birds.
Chapter Two addresses suggestions that some dinosaurs may have exhibited reproductive behavior similar to extant altricial birds, with highly dependant offspring. Comparisons of skeletal evidence from a variety of living archosaurian dinosaur relatives is shown to be consistent with a more crocodilian-like, precocial pattern of reproductive behavior. Chapter Three presents the two major contrasting perspectives on the phylogenetic relationships of various extinct archosaurs and birds, as well as a critical evaluation of the viable scenarios for the origin of avian flight. Current dogma notwithstanding, the supposed linear relationship between birds and theropod dinosaurs is demonstrated to be unlikely The fourth chapter is an experimental approach elucidating the water and heat savings mediated by nasal respiratory turbinates in a range of avian species. These structures are shown to have a significant functional role tightly correlated to the elevated metabolic rates characteristic of living endothermic vertebrates.
Collectively, this thesis uses a broad, multidisciplinary approach that draws from our knowledge of a range of biological parameters of extant vertebrates to provide a more complete, reasonable, and relevant perspective on the paleobiology of the dinosaurs.