The period of time before the Triassic was called the Permian. This was a time when ... sail-backed animal called dimetrodon, which looks like it could be a dinosaur but isn’t.

These large mammal-like reptiles lived during the Permian period as well, most likely during the early period around 260 million years ago. Dimetrodon fossils have been found across North America ...

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 Permian period’s mass extinction had wiped out the mammals that could have been competitors for these reptiles on land and in water. One example of these mammals would be the Dimetrodon ...