Neoceratopsia

Neoceratopsia is a clade of ceratopsian dinosaurs that takes in every member of the group except the earliest forms, Psittacosaurus and the chaoyangsaurids, and so encompasses all of the more derived horned dinosaurs. It spans small, basal taxa through to the large horned and frilled ceratopsids such as Triceratops. Within it, Euceratopsia unites the mostly small-bodied, largely North American Leptoceratopsidae with the more advanced ceratopsians, while the nested subgroup Coronosauria marks the first appearance of the bony neck frill and the fusion of the leading neck vertebrae to brace an increasingly heavy head. Neoceratopsians are set apart by a progressively enlarging skull and the growth of a frill extending back from the skull roof. Although the group originated in Asia, neoceratopsian fossils appear in North America by the middle of the Cretaceous, showing that it had dispersed across the Bering land bridge.