Ceratops (meaning "horn face") is a dubious genus of herbivorous ceratopsian dinosaur which lived during the Late Cretaceous. Its fossils have been found in the Judith River Formation in Montana. Although poorly known, Ceratops is important in the history of dinosaurs, since it is the type genus for which both the Ceratopsia and the Ceratopsidae have been named. The material is too poor to be confidently referred to better specimens, and Ceratops is thus considered a nomen dubium. History The first remains referred to Ceratops — an occipital condyle and a pair of horn cores — were found by John Bell Hatcher (1861–1904) in the late summer of 1888 near the Cow Creek in Blaine County in the uppermost Judith River Formation of Montana. Hatcher was at the time employed by Professor Othniel Charles Marsh who the same year named the find as the type species Ceratops montanus. The generic name was derived from Greek κέρας, keras, "horn", and ὤψ, ops, "face". The specific name referred to Montana. Marsh originally believed the animal to be similar to Stegosaurus, but with two horns on the back of its head, a body length of twenty-five to thirty feet, horizontal plates on its back and bipedal. According to Marsh it would have "represented a very strange appearance". In his illustration of the horn pair, purportedly showing them from behind, Marsh had switched their position and rotated their outside to the rear to make them point inwards. The holotype, USNM 2411, was found in a layer dating from the Campanian. It consists, apart from the occipital condyle, of two supraorbital horn cores of about twenty-two centimetres length. The right horn is attached to a part of the prefrontal. Marsh later referred two squamosals to the species, specimens USNM 4802 and USNM 2415. These however are more likely centrosaurine; they have also been referred to Avaceratops. In 1906 Richard Swann Lull noted that the name Ceratops had been preoccupied by a bird, Ceratops Rafinesque 1815, but also that this had been an undescribed nomen nudum, causing the name to have been still available in 1888. He nevertheless provisionally proposed a replacement name: Proceratops. This is thus a junior synonym of Ceratops. Already in the early twentieth century new finds made it increasingly difficult to distinguish the limited remains of Ceratops from several other related forms. Today, Ceratops is considered a nomen dubium. However, from time