Several geological and paleontological discoveries from these expeditions are still under development. Geologically, I wanted to generate hard data regarding the transition to dinosaur-dominated faunas during the Late Triassic. The new fossil evidence described below revealed that the initial dinosaur radiation occurred earlier than suspected, casting doubt on the competitive replacement model. Paleontological discoveries include the first complete skeletons of early dinosaurs. Eoraptor and Herrerasaurus were agile, bipedal predators with short forelimbs specialized for grasping and raking.
Eoraptor is structurally very close to the common dinosaurian ancestor.
Analysis of these fossils suggests that the dinosaurian radiation was well underway before dinosaurs dominated terrestrial vertebrate communities. These studies highlight the potential applications of broad-scale phylogenetics, with new insights outlined regarding the evolution of body size, trophic and locomotor adaptations, and biogeography. Portions of the phylogeny that involve major skeletal transformations are identified. The biogeographic history of dinosaurs is particularly interesting given the tectonic fragmentation of Pangaea during the latter half of the Mesozoic. Research into these questions has identified the major factors influencing historical biogeographic pattern and the unexpected dominance of regional extinction and dispersal over vicariance.