Protoceratops (meaning 'First Horne Face', derived from Greek proto-/πρωτο- 'first', cerat-/κερατ- 'horn' and -ops/-ωψ face) is a genus of sheep-sized (1.5 to 2 m long) herbivorous ceratopsian dinosaur, from the Upper Cretaceous Period (Campanian stage) of what is now Mongolia. It was a member of the Protoceratopsidae, a group of early horned dinosaurs. Unlike later ceratopsians, however, it lacked well-developed horns and retained some primitive traits not seen in later genera.