The early diversification of dinosaurs represents one of the most poorly known events of vertebrate evolution, and this period in the Late Triassic witnessed the origin of modern vertebrate groups and ecosystems, as well as a major mass extinction event. Our field research in the western USA is lead by Dr. Nate Smith and focuses on understanding the climatic, ecological, and macroevolutionary context of dinosaur origins, and elucidating how early aspects of the avian body plan were assembled. Detailed anatomical studies on early dinosaurs and dinosaur ‘precursors’ from our collaborative field project in Ghost Ranch, New Mexico have revealed that many of the morphological features unique to the avian hindlimb and respiratory system were already in place early in dinosaur evolution, possibly even by the ancient split of crocodiles and birds. Work at the Hayden Quarry in Ghost Ranch has also established that dinosaur ‘precursors’ were diverse taxonomically, and coexisted with dinosaurs for an extended (i.e., 10-15 Myr) period of time. New research is also suggested that the dichotomous pattern of early herbivorous dinosaur diversity at high vs. low latitudes may be driven in part by climate and plant community instability in tropical latitudes during the Late Triassic.
The last few decades have witnessed important discoveries in the field of dinosaur developmental biology and a dramatic change in our perception of how dinosaurs grew and developed. Our research on this topic has centered on the embryonic development, growth, and reproductive characteristics of several groups of dinosaurs. These studies have reported on the discovery of embryos and/or neonates of the long-necked sauropods and the carnivorous theropods (including birds), and they have documented different nesting strategies and behaviors for some of these dinosaurs. Paramount among these investigations has been the discovery and interpretation of Auca Mahuevo, an enormous Late Cretaceous sauropod nesting ground in Patagonia (Argentina) that has yielded significant information about the development and reproductive behavior of titanosaur sauropods.