Pachycephalosaurus

PALAEONTOLOGICAL RECORD

Pachycephalosaurus is a genus of pachycephalosaurid ornithischian dinosaur. The type species, P. wyomingensis, is the only known definitive species. The possibly synonymous taxon, Stygimoloch, might represent a distinct genus or a second species, P. spinifer. It lived during the Maastrichtian age of the Late Cretaceous period in what is now western North America. Remains have been excavated in Montana, South Dakota, Wyoming, and Alberta. Mainly known from a single skull and a few extremely thick skull roofs, Pachycephalosaurus is estimated to have reached 4.5 m (15 ft) long and weighed 370–450 kg (820–990 lb). More complete fossils would come to be found in the following years.

DISCOVERY

First fragments found in the 1850s in North America.

DIETARY PROFILE

Low browsing herbivore, chewing on leaves, seeds, and fruit.