If I was a 10 year old boy creating the ultimate mammal, I would probably start with a rhinoceros, then make it bigger, then give it 6 horns, then give it saber-teeth. Man that would be bad ass. Fortunately, such a creature once existed, and this is a museum quality cast of its skull. Mammal amblypod of the Eocene Uinta Formation of Colorado. It looks like a triceratops or other dinosaur, but it's a mammal. 29" x 13"
As is Skull fetures an excellent cranium but a damaged jaw.