Chasmosaurinae

Chasmosaurinae is one of the two subfamilies of horned ceratopsid dinosaurs, comprising the long-frilled forms of the Late Cretaceous of western North America (Laramidia). Its members are distinguished by prominent, elongate brow horns, reduced nasal horns, and long frills that lack the long spines seen in their short-horned relatives the centrosaurines. Chasmosaurines first appeared in the early Campanian and persisted until the Cretaceous–Paleogene extinction that ended the age of non-avian dinosaurs, and their remains are known from western Canada, the western United States, and northern Mexico. The group was highly diverse, ranging from earlier forms such as Chasmosaurus and Pentaceratops to the derived and often gigantic Triceratopsini, which includes Triceratops, Torosaurus, and their close relatives. The distinctive shape of the frill and the small hornlets along its margin allow many species to be recognized even from fragmentary remains, contributing to the group's high named diversity.