Pachycephalosauria (Greek for "thick headed lizards") is a group of ornithischian dinosaurs which evolved during the Cretaceous period in what is now North America and Asia.
Pachycephalosauria (Greek for "thick headed lizards") is a group of ornithischian dinosaurs. This group of ornithischian dinosaurs evolved during the Cretaceous period in what is now North America. This group of ornithischian dinosaurs evolved during the Cretaceous period in what is now Asia.