End of Cretaceous extinction: The end of the dinosaurs

Abstract

The age of dinosaurs saw great proliferation of these reptiles, as well as a general increase in maximum size through much of the Mesozoic. It also saw the emergence of flying reptiles and birds, and the return of some land reptiles to an aquatic existence. These were generally gradual changes leading to a progressively more complex global ecosystem. This was suddenly ended at the end of the Cretaceous Period about 65 million years ago in yet another major extinction event, the so-called K-T extinction. It appears likely that this was, indeed, a very sudden event: the impact of a large asteroid on the Earth. The dinosaurs were wiped out (except to the extent that one wishes to consider birds a form of dinosaur!), and the age on mammals began.