Clade of ornithischian dinosaurs, considered a sister clade to Ornithopoda. Characterized by an abbreviated posterior portion of the premaxillary as it contributes to the palate and a shortened pubis accompanied by widely spaced hip sockets. Includes clades Pachycephalosauria and Ceratopsia.

Suborder which is classified into ceratopsians and pachycephalosaurs (Cretaecous).

includes bone-headed (pachycephalosaurs) and horned (ceratopsian) dinosaurs

"bordered heads." These animals all have some kind of bony frill at the back of the skull. The group includes the pachycephalosaurs and ceratopsians.

Marginocephalia ("fringed heads") is a clade of ornithischian dinosaurs that includes the thick-skulled pachycephalosaurids, and horned ceratopsians. They were all herbivores, walking on two or four legs, and are characterized by a bony ridge or frill the back of the skull. The clade evolved in the Jurassic period, and became common in the Upper Cretaceous.