Some pachycephalosaurs lived in Asia, but Pachycephalosaurus roamed the North American West. Like all of its cousins, it was a plant eater that walked on its hind legs. Pachycephalosaurus was not as quick as its smaller relatives, but compared to the giant duckbills and horned dinosaurs in its world, it was quite speedy. And its eyes were set forward in its skull, giving pachycephalosaurs good 3-D vision.

Pachycephalosaurus is often shown butting heads with its rivals, like bighorn sheep do today. But scientists believe that it could not have survived banging heads. Instead, they suggest that these dinosaurs may have whacked each other in the sides with their thick heads. Why? Maybe it was competition for territory or mates.

Text by "Dino" Don Lessem