Pachycephalosaurus

FACT SHEET: pachycephalosaurus

NAME: PACHYCEPHALOSAURUS (PAK-ee-kef-AH-loh-SAW-rus), "Thick-Headed Lizard" SIZE: 15 feet long, 6 feet tall (the size of a minivan), weighed 950 pounds TYPE OF DIET: Herbivore (plant leaves, fruit, seeds) WHEN: Late Cretaceous period (70 million years ago) WHERE: Montana (N.America), Alberta (Canada), Mongolia (Asia), Madagascar (Africa)

Pachycephalosaurus lived about 70 million years ago. It was a medium-sized dinosaur, about 15 feet long. It was a strange-looking dinosaur with an odd dome-shaped head. Its skull was very thick, with about eight inches of bone on top and spiky bones around the edges. This is how it got its name, which means “thick-headed lizard”. Underneath all that thick bone, however, was a very small brain. Paleontologists still don’t really know what these creatures did with their hard heads. At first they believed that Pachycephalosaurs used their heads to butt each other, the way big-horned sheep do. But after studying the skull carefully, paleontologists know that it was not very strong. If two Pachycephalosaurs tried to butt heads, they would almost certainly hurt each other badly. Now we believe that they rammed into other dinosaurs’ sides. They probably rammed hunting predators when there was nowhere left to run. Pachycephalosaurus was not a very fast runner. It probably held its heavy head close to the ground. It may have walked on all four legs while it was looking for food. Pachycephalosaurus was an herbivore, eating soft plants, fruit, and seeds. Pachycephalosaurus had large holes in its skull for eyes, so it could see very well, possibly even at night. It might have moved around in small groups and lived on the coasts, near the ocean. Its bones were found in what is now Montana, in the western United States. Other fossils have been found in what is now Alberta, Canada, Mongolia and Madagascar.