[D] Cerasinops hodgskissi [Su] [sG] [T]
Chinnery and Horner 2007
Cretaceous Late Campanian
Ornithischia Genasauria Cerapoda Marginocephalia Ceratopia Neoceratopia
Lower Two Medicine Formation of Montana, US
Genus - Typespecies - Skull
Holotype Specimen: MOR (Museum of the Rockies) 300, associated skull and skeleton, about 80% complete. Included with the specimen are the basioccipital and basisphenoid fused together, the left paroccipital process with the exoccipital, prootic, and caudal portion of the laterosphenoid fused, the right exoccipital, and the unfused supraoccipital; both partial maxillae; both palpebrals; nearly complete left and partial right jugals; left and partial right quadratojugals; fused left and right frontals and partial left postorbital; right and left squamosals and partial parietal; most of the right quadrate and part of the left; both mandibles; most of the cervical, dorsal, and sacral vertebrae, several of the caudal vertebrae, the majority of the ribs, both scapulae, the left coracoid, both humeri, right and partial left ulnae, both radial shafts, fragmentary manus elements, very fragmentary pelvic elements, right and partial left femora and tibiae, right fibula, astragalus, calcaneum, and left pes are preserved.
USNM (United States National Museum) 13863 and 13864, both partial skeletons previously referred to Leptoceratops sp. (Gilmore, 1939). The specimens are referred based on similarity of skull elements including the basisphenoid, parietal, postorbital, maxilla, pterygoid, surangular, and quadrate. The surangular is especially diagnostic in Cerasinops, as it is extremely robust and has a thick buttress that contacts the coronoid process. These unique characters are found on both MOR 300 and USNM 13864 surangulars.
The genus name is from cerasinus (L., of cherry) + -ops (L., face), or ‘face of cherry’ referring to the red beds of the type locality and the dark red tinge of color on the specimen. This name also incorporates the nickname Cera, by which the specimen has been referred for over two decades. The species name refers to Wilson Hodgskiss, on whose property the specimen was discovered.
Horizon and Locality
The locality of the holotype specimen is Museum of the Rockies TM-012, Red Rocks Site, Teton County, Montana. Both referred specimens were excavated from a site designated as Locality TM-067, Pondera Co., Montana. All specimens are from the lower Two Medicine Formation (Campanian Stage), between ash beds dated at 76.5 and 80.0 mya (Rogers et al., 1993; Horner et al., 2001).
Basal (cladistically) neoceratopsians are relatively small, gracile members of Ceratopia (\\\\\\\'horned\\\\\\\' dinosaurs), which also includes larger forms such as Triceratops and Centrosaurus. The Asian basal neoceratopians share some very important traits not found in any North American group until now, including a fenestrated frill and premaxillary teeth. Likewise, the North American basal taxa have some traits not found in the Asian forms, the most important of which is a very specialized tooth wear pattern.
Cerasinops hodgskissi, is a basal Neoceratopian that exhibits all of the above characters along with others previously found on only one of the two continents. The new species is a sister group to [Leptoceratopsidae] in a cladistic analysis, and is a link between the taxa on the two continents. Cerasinops also exhibits extremely interesting anatomical and histological features that indicate the possibility of bipedality in this taxon, a locomotor pattern not found previously in basal neoceratopians.
Member of Neoceratopsia with a unique character combination including: basioccipital tubera intermediate in shape between those of Protoceratops and Montanoceratops, a prootic that extends further caudally than in either Protoceratops or Montanoceratops, straight nasal, a short but high frill based on shape of the squamosal, deep posttemporal depression relative to that of other basal neoceratopsians, horizontal jugal crest in addition to the typical vertical one, a uniquely-shaped quadratojugal, extremely robust surangular relative to those of other basal forms, a narrow coronoid process of the mandible, and pronounced medial bend of the distal ulna.
The specimen also has a low forelimb to hindlimb ratio (0.60, lower than in any other basal neoceratopsian), as well as unique bone histology of the forelimb elements (the forelimb elements have a longitudinal canal structure, relative to the circumferential structure found in the hind limbs and in all limbs of the comparison taxa).