Pachycephalosaurus was a pachycephalosaur (or thick-headed dinosaur) that lived in North America. It was one of the last non-avian dinosaurs before the Cretaceous-paleogene extinction event about 65 million years ago. It is distinctive for the reinforced dome of its skull, leading to speculation that they used to fight each other by head-butting. This has more recently been countered with the suggestion of flank-butting.
Discovery
Pachycephalosaurus fossils may have been discovered in 1850 in the Lance Formation in south-eastern Montana. Early finds were fragmentary, but more complete specimens have recently been recovered.
Paleoecology
Pachycephalosaurus lived on what were floodplains. Its sharp separated teeth would have made it ideal for a mixed-plants diet, and capable of shredding leaves.
