Ceratopsidae

Ceratopsidae is a family of large, quadrupedal, herbivorous ceratopsian dinosaurs that lived during the Late Cretaceous, including well-known forms such as Triceratops, Centrosaurus, and Styracosaurus. Nearly all known species come from western North America, which formed the island continent of Laramidia at the time, ranging from Alaska to Mexico; the sole named exception is Sinoceratops, from China. Ceratopsids are recognized by their toothless beaks, rows of shearing teeth packed into batteries at the back of the jaw, elaborate nasal and brow horns, and a thin parietal-squamosal shelf that sweeps back and up into a bony frill. The family is split into two subgroups: the chasmosaurines, which typically bear long triangular frills and well-developed brow horns, and the centrosaurines, which have prominent nasal horns or bosses, shorter and more rectangular frills, and elaborate spines along the frill margin. These horns and frills vary enormously between species and were likely display structures used to signal to rivals and mates, though some may also have served in combat or defense. Many centrosaurines are found in dense bone beds, suggesting that these animals gathered in large herds.