One study explains how 270 million years ago, two different mammal relatives could have exhibited interspecies combat behaviors similar to today’s deer.

With faces pretty enough to turn you to stone, and a pair of saber-teeth to slash at their prey, the gorgonopsians truly lived up to their frightful name. They were the lords of the Late Permian, a time when every single continent was beginning to drift together, forming the supercontinent of Pangaea.