(pak-ee-SEF-uh-lo-sawr-us)
This dinosaur was a very large member of the "bonehead" family. All members of the family had thick skulls. Some had a thick knob on top of the skull that looked like a crash helmet. Some of these animals were quite small, less than 3 feet in size. A relative, Homalocephale, was 10 feet long. Pachycephalosaurus was the biggest of the boneheads and towered above its relatives. It also had the thickest skull, with which it could charge its enemies and knock them senseless. There was only one problem with a thick skull. It left little room for brains!
Scientists have carefully measured the skull of different boneheads and found that Pachycephalosaurus had a dense cap of bone 10 inches thick. It had some small, bony spikes jutting up from its nose and sharp knobs around the back of its head. Charging at full speed, it would have made a terrific impact. It may also have used its head to ram others in its family. Some animals do this today to claim territory or to warn off others. Pachycephalosaurus lived in North America, but others in the large family have been found all over the world.
Diet: Plants
Size: Length 4.6m (15 ft)
Classification:
Family Pachycephalosauridae
Infraorder Pachycephalosauria
Suborder Marginocephalia
Order Ornithischia
Time (million years ago): 68-65