Abstract

Dinosaurs are some of the most celebrated icons of evolution and extinction. They dominated terrestrial ecosystems during much of the Mesozoic, some reaching colossal sizes larger than any other land-living organisms, before going extinct at the end of the Cretaceous. Much of my research focuses on the evolutionary history of dinosaurs. Dinosaurs evolved from small, fast-running reptiles in the immediate aftermath of the end-Permian extinction, but remained rare and ecologically marginal until the Late Triassic. During the entire Triassic they were eclipsed on land by crocodile-line reptiles, which were more diverse, ecologically disparate, and globally widespread than dinosaurs. The end-Triassic extinction suddenly killed off most crocodile-line archosaurs, giving dinosaurs the opportunity to become dominant creatures in the Early Jurassic. It was at this time that dinosaurs truly became pre-eminent, by spreading across the globe, evolving into a range of niches, and developing colossal size. Dinosaurs were the dominant terrestrial vertebrates for the next ~130 million years before they suddenly went extinct at the end of the Cretaceous. Dinosaur faunas were apparently undergoing dramatic changes during the final 12 million years of the Cretaceous, before an asteroid impact delivered a final coup de grace. One group of dinosaurs, however, survived: the birds. Dinosaurs are therefore present in today’s world as 10,000 species ranging from pigeons to peacocks.