Evolution and phylogenetic relationships of the early cerapodan dinosaurs

Cerapodans are a major group of herbivorous bipedal and quadrupedal ornithischian dinosaurs that dominated the terrestrial herbivorous niche during the Cretaceous. Early in their evolutionary history they split into two major groups, the ornithopods (duck-billed dinosaurs and their relatives) and the marginocephalians (horned and frilled dinosaurs and dome-headed dinosaurs). Subsequent to the split both groups radiated and developed complex chewing mechanisms and social structures that allowed them to achieve high diversity and abundance, and their fossils are well-known from outstanding material. However, early representatives of Cerapoda are known from much more fragmentary remains, and this has hindered our understanding of their taxonomy, relationships, and evolution. In particular, the ontogenetic status of many of the early cerapodans is unknown, and their fragmentary fossil record means that character transitions at the base of Cerapoda remain unclear. This has limited our interpretation of the evolution of mega-herbivory and quadrupedality in these dinosaurs. Competing phylogenetic hypotheses indicate radically different evolutionary relationships for early cerapodans, and it remains particularly unclear which taxa are included within Ornithopoda.
The aim of this project is to conduct a comprehensive anatomical and systematic evaluation of all basal cerapodans and resolve phylogenetic uncertainties, providing a robust evolutionary tree. This tree will then be used to investigate the evolutionary history of Cerapoda with a focus on palaeobiogeography, diversity through time, and the timings of major divergences and radiations. Key research aims include: (1) resolving the taxonomy of key basal cerapodans, with a particular focus on North American Late Jurassic taxa; (2) examining the ontogenetic status and population ecology in a large sample of Early Cretaceous British taxa; (3) determining the phylogenetic position of basal cerapodans relative to the divergence of Ornithopoda and Marginocephalia; (4) using the resulting hypothesis to explore biogeographic and diversity patterns through time.