The Pachycephalosaurus was a bipedal herbivorous dinosaur that belonged to the genus of pachycephalosaurids. It lived during the Late Cretaceous Period (Maastrichtian stage) in North America, and remains have been excavated in Montana, South Dakota, Wyoming, Alaska, and Alberta. The Greek translation of its name means ”thick-headed lizard” refers to the Pachycephalosaurus’s extremely thick skull roof. Other physical features were a thick neck, short forelimbs, long hindlimbs, a bulky body, and a heavy tail held rigid by ossified tendons. It has been commonly hypothesized that the Pachycephalosaurus used their skulls in combat, similar to the bighorn sheep or musk oxen’s use of their heads to transmit stress during ramming, but this has been disputed in recent years.