CERATOPSIAN

also called Ceratopian, any of a group of plant-eating dinosaurs of the Cretaceous Period (144 to 66.4 million years ago), characterized by cranial horns and a beaklike mouth. The suborder Ceratopsia comprises three families: Psittacosauridae, the most primitive and often hornless; Protoceratopsidae, including Protoceratops and Leptoceratops; and Ceratopsidae, including Triceratops and Torosaurus. The term ceratopsian literally means horn face, referring to the fact that most of these dinosaurs had large horns on the snout or brow; some, especially the ceratopsids, also had horns arrayed along the rear margin of the skull frill, a pronounced bony expansion over the neck region.