He transforms into a "Pachycephalosaurus". Assisting Barnum Brown, he co-described "Pachycephalosaurus" and what is now "Montanoceratops". The anatomy of "Pachycephalosaurus" is poorly known, as only skull remains have been described. Remains attributable to "Pachycephalosaurus" may have been found as early as the 1850s. The first two might be junior synonyms of "Pachycephalosaurus". Like the Pachycephalosaurus, it is also attracted to the light of the sun. "Pachycephalosaurus wyomingensis" is currently the smallest playable herbivore planned for Saurian. It has been estimated that "Pachycephalosaurus" was about long and weighed about . "Pachycephalosaurus" is the largest-known pachycephalosaur. "Dracorex" and "Stygimoloch" have been synonymized with "Pachycephalosaurus". "Pachycephalosaurus" had a small muzzle which ended in a pointed beak. Within the tribe Pachycephalosaurini, "Pachycephalosaurus" is most closely related to "Alaskacephale". "Pachycephalosaurus" will subsist on an herbivorous diet composed of low-lying vegetation. Like other pachycephalosaurids, "Pachycephalosaurus" was a bipedal herbivore with an extremely thick skull roof. "Pachycephalosaurus" was so unusual that Sternberg named a new family for it, the Pachycephalosauridae.