Not much hair, just a few bristles, but it’s still there. Some mammals are small and live near you. Like dogs and cats who have soft hair or fur. And hamsters, hedgehogs and rats and even bats.

"It didn't have any fur, and it wouldn't have had dog-like ears." Just like mammals today, this this 1 meter (3 foot) long gorgonopsian had jaw-muscle attachment holes on the sides of their skull.

Prairie dogs live in underground burrows, extensive warrens of tunnels and chambers marked by many mounds of packed earth at their surface entrances. Burrows have defined nurseries, sleeping ...