Sampson & Carrano Theropods are a diverse clade of predatory dinosaurs with a global distribution and a lengthy Mesozoic tenure (also persisting to the present day in the guise of birds). A basal division into two monophyletic taxa, Ceratosauria and Tetanurae, has been supported since publication of the first rigorous analysis of the group 12 years ago. Yet most systematic studies of theropods have focused on a single derived subclade within Tetanurae (Coelurosauria), due in large part to ongoing controversy over the origin of birds. The few more inclusive analyses of theropods conducted to date have underscored the poor resolution of relationships among ceratosaurians and basal tetanurans. A major objective of the proposed research is to conduct an exhaustive analysis of the historical relationships of basal theropods, including virtually all known genera. This study, based almost entirely on firsthand examination of specimens representing more than 60 taxa, will constitute by far the most extensive investigation of the systematics of ceratosaurians and basal tetanurans. It will also include the first genus-level cladistic assessments for several theropod clades. The second, related objective is to assess the stability of the tree(s) resulting from the phylogenetic analysis, and compare these results with those of previous analyses of theropod relationships. The resulting analyses will be richly illustrated with osteological drawings and descriptions. The significance of the study goes well beyond the fundamental insights it will provide into the systematic relationships and osteology of theropod dinosaurs. A robust phylogeny is prerequisite to any higher-order inferences relating, for example, to functional morphology or biogeography. Ultimately, phylogenetic and stratigraphic data can be compared with geophysical data to investigate the large-scale pattern and timing of Pangean fragmentation. Moreover, this project will constitute a prime case study in the analysis of missing data using a large paleontological data set.
