| Ceratops | |
|---|---|
 | |
| Holotype left horncore | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Ceratopsia |
| Family: | †Ceratopsidae |
| Subfamily: | †Ceratopsinae Marsh, 1888sensuAbel, 1919 |
| Genus: | †Ceratops Marsh, 1888 |
| Species: | †C. montanus |
| Binomial name | |
| †Ceratops montanus Marsh, 1888 | |
| Synonyms | |
| |
Ceratops (meaning'horn face') is adubiousgenus of herbivorousceratopsiandinosaur which lived during theLate Cretaceous. Its fossils have been found in theJudith River Formation inMontana. Although poorly known,Ceratops is important in the history of dinosaurs, since it is thetype genus for which both theCeratopsia and theCeratopsidae have been named.
The first remains referred toCeratops — anoccipital condyle and a pair ofhorn cores — were found byJohn Bell Hatcher (1861–1904) in the late summer of 1888 near theCow Creek inBlaine County in the uppermostJudith River Formation of Montana. Hatcher was at the time employed by ProfessorOthniel Charles Marsh who the same year named the find as thetype speciesCeratops montanus. The generic name was derived from Greek κέρας,keras, "horn", and ὤψ,ops, "face". Thespecific name referred to Montana. Marsh originally believed the animal to be similar toStegosaurus, 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".[1] 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.[2]
The holotype,USNM 2411, was found in a layer dating from theCampanian. It consists, apart from the occipital condyle, of two supraorbital horn cores of about twenty-two centimetres length.[2] The right horn is attached to a part of the prefrontal. Marsh later referred twosquamosals to the species, specimens USNM 4802 and USNM 2415. These however are more likelycentrosaurine; they have also been referred toAvaceratops.[3]
In 1906Richard Swann Lull noted that the nameCeratops had been preoccupied by a bird,Ceratops Rafinesque 1815, but also that this had been an undescribednomen nudum, causing the name to have been still available in 1888. He nevertheless provisionally proposed a replacement name:Proceratops.[4] This is thus ajunior synonym ofCeratops.
Already in the early twentieth century new finds made it increasingly difficult to distinguish the limited remains ofCeratops from several other related forms. Today,Ceratops is considered anomen dubium.[5] However, from time to time claims are made about discoveries that, also taking into regard their provenance, might have a provable connection with theCeratops holotype.
In 1995,David Trexler and F.G. Sweeney noted that complete material from a bonebed that had been found inMontana could enableCeratops to be reexamined. The site, known as the Mansfield Bonebed, belongs to the same stratigraphic level as the one that yielded the originalCeratops remains. It had initially been interpreted as containingStyracosaurus, but what earlier authors considered the frill spikes ofStyracosaurus turned out to be chasmosaurine orbital horns. Trexler and Sweeney pointed out that these horns closely resembled those ofCeratops, and could allow the genus to be rescued as a valid name.[6] The ceratopsids in the bonebed were later referred to the genusAlbertaceratops, and later re-classified in their own genus,Medusaceratops.[7]
In 1999,Paul Penkalski andPeter Dodson concluded thatCeratops, despite being anomen dubium because the material is too meager, appeared closely related toAvaceratops which may even be a juvenileCeratops; there is not enough material to prove it.[8]
In 1889 Marsh named a second species ofCeratops:Ceratops horridus.[9] This would almost immediately in a subsequent article be renamed intoTriceratops horridus.Ceratops horridus is thus the type species ofTriceratops. In the same article Marsh renamedBison alticornis, his misidentification of ceratopsid material for a giantbovid, intoCeratops alticornis.[10] In 1890 Marsh renamedHadrosaurus paucidens intoCeratops paucidens;[11] but the original assessment of Hatcher that this representedhadrosaurid material is probably correct.[2]
In 1905 Hatcher renamed threeMonoclonius species intoCeratops species:Monoclonius recurvicornis Cope 1889 becameCeratops recurvicornis;Monoclonius belli Lambe 1902 was madeCeratops belli andMonoclonius canadensis Lambe 1902 was renamedCeratops canadensis.[12]C. canadensis later was made the separate genusEoceratops, andC. belli was made the separate genusChasmosaurus; in 1925William King Gregory concluded thatCeratops andChasmosaurus were identical,[13] but this was rejected by most researchers.
In 2005, remarkably well preserved cranial and postcranial elements of aJudithian ceratopsian were discovered inFergus County, Montana. Nicknamed "Judith", preliminary examination suggested a close affinity withC. montanus. The locality has been determined to be on or in close proximity to the stratigraphic layer ofC. montanus, and not too many miles away.[14] In 2016, the new animal was namedSpiclypeus, and the authors stated that it may be identical toCeratops, which they considered anomen dubium, or a growth stage ofAlbertaceratops.[15]
The naming history can be summarised in a species list.
Ceratops was placed by Marsh in theCeratopsidae in 1888.[1] It thus belonged to the Ceratopsia, a group of herbivorous dinosaurs withparrot-like beaks which thrived inNorth America andAsia during the LateCretaceous Period, which ended roughly 66 million years ago. In 1919 the groupCeratopsinae was named byOthenio Lothar Franz Anton Louis Abel,[16] but this concept is problematic:Paul Sereno has defined it as equivalent to theChasmosaurinae but other researchers limit it toCeratops itself as its direct relationships are uncertain.
Ceratops, like all ceratopsians, was aherbivore biting off plant material with its beak and processing it with its tooth batteries.
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