The story of dinosaur evolution appears, therefore, to have been driven by three enormous extinctions caused by rapid, traumatic and massive environmental change. The first, at the end of the Permian, created environmental space for dinosaurs to evolve. The second, at the end of the Triassic, allowed dinosaurs to rise to dominance and evolve seemingly unfeasible body sizes. And the third, at the end of the Cretaceous, brought the dinosaurs their doom. As we head into another mass extinction, this time driven by humans, the fossil record, including that of dinosaurs, provides unique insights into the role of mass extinction in shaping and altering the course of evolutionary history.