ceratopsian

Any of various dinosaurs of the group Ceratopsia of the late Jurassic and Cretaceous Periods. Ceratopsians were ornithischians characterized by skulls with a parrotlike beak, a broad bony frill extending back over the neck, and often one or more horns. Most ceratopsians walked on all fours and grew to medium or large size. Triceratops was a ceratopsian.