Ceratopsia

Ceratopsia is a group of beaked, herbivorous ornithischian dinosaurs, popularly known as the horned dinosaurs, that lived from the Late Jurassic to the end of the Cretaceous across what are now Asia, North America, and Europe. Every member carries a rostral bone, a toothless ossification capping the upper jaw that pairs with the predentary of the lower jaw to form a parrot-like beak found in no other dinosaurs. The skull is further marked by prominent jugal bones that flare outward beneath the eyes, giving it a triangular outline from above. The earliest forms, such as Psittacosaurus and the Chaoyangsauridae, were small bipedal animals, while later members grew into very large quadrupeds that developed elaborate facial horns and neck frills. The most derived members, the ceratopsids like Centrosaurus and Triceratops, were among the dominant herbivores of their environments, with the group as a whole spanning animals from about a meter long to over nine meters.