In the Eocene Epoch, there was a reptile that had teeth equipped for biting through flesh, its hind legs were a lot longer than its front legs and instead of claws, its toes were each capped with hooves. How did this living nightmare...

From the long extinct Stegosaurus, to tiny modern mice, all sorts of animals grow bits of bones inside their skin. These structures are called osteoderms, and they're often more than just a suit of armor.