ceratopsid

Ceratopsids are a family of herbivorous dinosaurs within the larger clade Ceratopsia. They lived during the Cretaceous period in Asia and North America, from the Early to Late Cretaceous and continuing until the end of the period about 66 million years ago. Ceratopsids are best known for their distinctive skulls, which typically feature a beaked mouth, a battered set of teeth for processing vegetation, and a large frill extending from the back of the skull. Many species also bore horns on the face or above the eyes, and several possess elaborately ornamented frills.

Anatomy and classification. The ceratopsids are divided into two main subfamilies: Centrosaurinae and Chasmosaurinae. Centrosaurines generally have more elaborate frill ornamentation and shorter nasal horns, while chasmosaurines tend to display longer brow horns and larger frills. Common features across the family include a beaked bill, dental batteries for grinding plant material, and a robust skull that supported the frill and horns. The frill and horns are interpreted as adaptations for display, species recognition, and possibly intraspecific combat, rather than primary defense.

Representative genera. Notable ceratopsids include Triceratops, Torosaurus, and Chasmosaurus (exemplifying the chasmosaurines), and Centrosaurus, Styracosaurus, and Einiosaurus (representing the centrosaurines). Pachyrhinosaurus is known for a prominent nasal boss rather than horns. The group is primarily known from North American fossil deposits, with earlier or related forms appearing in Asia.

Paleobiology and extinction. Ceratopsids were among the most diverse and ecologically successful herbivores of the late Cretaceous. They likely traveled in herds and used their horns and frills in social interactions. They disappeared at the Cretaceous–Paleogene boundary, alongside many other dinosaur groups.