About 250 million years ago, at the end of the Permian period, something killed some 90 percent of the planet's species. Less than 5 percent of the animal species in the seas survived. On land ...

The period of time before the Triassic was called the Permian. This was a time when a wide variety of animals lived, including a group of animals called the synapsids, which would later evolve ...

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 ...