Pachycephalosaurus was a genus of dinosaur which lived during the last five million years of the Upper Cretaceous. It lived in what is now North America.
This member of the Pachycephalosaurid family is known from a single skull and a few thick skull roofs. From this it is estimated that its length was about 4.5 to 5 metres long (about 15 feet).
Pachycephalosaurus was a herbivore. It lived on a mixed diet of leaves, seeds, and fruit. The sharp, serrated teeth would have been very effective for shredding plants.