Vertebrate Paleontology. During much of my career I have studied the anatomy, phylogeny and relationships of Paleozoic amniotes. These fossils not only record the first successful adaptation of vertebrates to a fully terrestrial mode of life, but are also at the base of subsequent adaptive radiations that eventually gave rise to modern reptiles, birds and mammals. These fossils therefore provide a unique opportunity for studies of the origin and evolutionary radiation of all amniotes.

I have also studied the anatomy, embryology and growth, and evolutionary relationships of a variety of other vertebrates, including lungfish, dissorophoid amphibians, diadectomorph tetrapods, and basal dinosaurs.