🪖Pachycephalosaurs

Dome-headed dinosaurs

Ornithischia › Marginocephalia › Pachycephalosauria

Pachycephalosaurs had thick, round domes on their heads, like built-in helmets. Scientists think they may have bonked heads or pushed each other with them. They walked on two legs and mostly ate plants.

Pachycephalosaurs ("thick-headed lizards") are marginocephalian ornithischians, close relatives of the ceratopsians, known mainly from the Late Cretaceous of North America and Asia. In Pachycephalosaurus the solid skull roof could be over 20 cm thick. Whether they butted heads is still debated: some scientists argued the domes were too rounded for direct impacts, but healed injuries found on many domes support some form of head-to-head or head-to-body combat. Another debate concerns growth, since the flat-headed Dracorex and spiky Stygimoloch may simply be young Pachycephalosaurus whose skulls changed shape as they matured.