The recently acquired skull of the dome-headed dinosaur Pachycephalosaurus. USNM PAL 803273, Department of Paleobiology, Smithsonian Institution. Gift of Eric and Wendy Schmidt. Photo by James D.

Jurassic Park helped popularize this head butting dino. Learn why paleontologists are undecided about the evolution and behavior of the Pachycephalosaurus. Partway down the list of household dinosaur ...

Pachycephalosaurus wyomingensis was the largest of the pachycephalosaurids—"thick-headed dinosaurs"—which featured extremely thick skullcaps. The top of a Pachycephalosaurus skull could be 9 inches ...

Pachycephalosaurus, the delicately built, 15-foot-long, dome-headed dinosaur that lived alongside Tyrannosaurus and Triceratops, is a staple of children’s books and popular culture—one usually ...