Entelodonts

Entelodonts spent a lot of time fighting with their own kind. Many entelodont skulls have very severe wounds - some have gashes up to 2cm deep in the bone between the eyes - which can only have been inflicted by other entelodonts during fights. In fact it seems to have been quite common for one to fit another's head entirely in its mouth! The bony lumps all over their faces, like those of modern warthogs, were designed to protect delicate areas during these fights. This seems to have worked well, since even very scarred entelodonts show no damage to the protected eyes or nose.