Anatomy and palaeobiology of Thecodontosaurus antiquus (Dinosauria, Sauropodomorpha) and its implications for early dinosaur evolution

Abstract

The Mesozoic is commonly known as the Age of Dinosaurs, an era when this clade dominated ecosystems on land and explored myriad and unique ecological niches. The diversity and evolution of dinosaurs after their rise to ecological dominance in the Jurassic and Cretaceous centres our current knowledge, but their early evolutionary stages during the Late Triassic remain poorly resolved in comparison. This period was key in the radiation of the clade, when dinosaurs diversified their body plans and certain lineages underwent important evolutionary transitions. In this thesis, I explore the early functional diversity and evolution of dinosaurs using Thecodontosaurus antiquus, an early sauropodomorph from the Rhaetian of Britain, as a study case. First, I describe the osteology of Thecodontosaurus based on new fossil material, updating the diagnosis of the species. Second, I reconstruct the neuroanatomy and appendicular musculature of Thecodontosaurus using Computed Tomography and comparative anatomy. The endocranial morphology and limb muscle arrangement of Thecodontosaurus suggest that it was bipedal and cursorial, and hearing ability estimations indicate some degree of social behaviour. Based on these findings, I discuss important evolutionary modifications in the osteology, neuroanatomy and myology of Sauropodomorpha and their palaeobiological implications. Finally, I investigate the dietary diversity of early dinosaurs based on quantitative analyses of their dentitions, using a combination of geometric morphometrics, finite element analysis and machine learning classification. My results reveal the trophic diversity during early dinosaur evolution, including carnivores, omnivores and herbivores. Early saurischians were carnivores, sauropodomorphs experienced an evolutionary transition from carnivory to herbivory during the Late Triassic, and omnivory was the likely diet of early ornithischians. In conclusion, this thesis highlights the importance of a multifaceted approach to functional palaeobiology, and contributes to the growing understanding of the functional diversity and ecological evolution of dinosaurs during the key stage of their evolutionary radiation.

Date of Award	6 Dec 2022
Original language	English
Awarding Institution	The University of Bristol
Supervisor	Emily J Rayfield (Supervisor) & Michael J Benton (Supervisor)