About 250 million years ago, at the end of the Permian period, something killed some ... we would have seen animals as abundant and diverse as those of today's Serengeti, except most would have ...

Therapsids, the ancient relatives of mammals, once roamed Earth in great numbers during the middle to late Permian period.

Among them were the chordates, to which vertebrates (animals with backbones ... survived until the mega-extinction that ended the Permian period 251 million years ago. A predator of the Cambrian ...

Nobu Tamura/Wikimedia Commons The Triassic Period (252-201 million years ago) began after Earth's worst-ever extinction event devastated life. The Permian-Triassic extinction ... a group of animals ...

The Permian period’s mass extinction had wiped out ... At first, these creatures were much smaller, but they eventually outgrew other animals such as the Lystrosaurus, a dog-sized animal that ...