Behind the dinosaurs was a case with skulls of Permian synapsids. They don't get many visitors. Lystrosaurus, the synapsid that inherited the barren world of the Triassic, stared out empty-eyed.

And while these iconic animals no longer walk this earth, their legacies live on all across the continents, with one tiny ...

One member of this group was a large, sail-backed animal called dimetrodon, which looks like it could be a dinosaur but isn’t. Then 252 million years ago came the Permian-Triassic extinction event.

This also marked the first time the earliest dinosaurs appeared. The Permian period’s mass extinction had wiped out the mammals that could have been competitors for these reptiles on land and in ...