Euceratopsia

Euceratopsia is a clade of neoceratopsian dinosaurs that groups the more derived horned forms while excluding the most basal members of that lineage. Defined as the smallest group containing Leptoceratops, Protoceratops, and Triceratops, it brings together the Leptoceratopsidae — a mostly North American assemblage of small-bodied, quadrupedal ceratopsians — with Coronosauria and all more advanced ceratopsians. The coronosaurs within it show the first development of the neck frill and the fusion of the first several neck vertebrae to support an increasingly heavy head, a trend that reaches its extreme in the large, horned ceratopsids of the Late Cretaceous.