World’s greatest mass extinction triggered switch to warm-bloodedness

The origin of endothermy in synapsids, including the ancestors of mammals. The diagram shows the evolution of main groups through the Triassic, and the scale from blue to red is a measure of the degree of warm-bloodedness reconstructed based on different indicators of bone structure and anatomy. Mike Benton, University of Bristol. Animal images are by Nobu Tamura, Wikimedia Posture shift at the end of the Permian, 252 million years ago. Before the crisis, most reptiles had sprawling posture; afterwards they walked upright. This may have been the first sign of a new pace of life in the Triassic. animal drawings by Jim Robins, University of Bristol 16 October 2020 Mammals and birds today are warm-blooded, and this is often taken as the reason for their great success.