Describer

Longrich 2010

Time

Cretaceous Late Campanian

Classification

Ornithischia Genasauria Cerapoda Marginocephalia Ceratopia Neoceratopia Ceratopidae Chasmosaurinae

Diet

Herbivore

Fossilsite

Dinosaur Park Formation > Judith River Wedge ,Alberta, Saskatchewan, Canada

Info

Mojoceratops perifania (Longrich 2010) > Eoceratops canadensis (Lambe, 1915) Chasmosaurus kaiseni (Brown, 1933)

Abstract

A new genus of long-horned chasmosaurine ceratopsid is described from the Dinosaur Park Formation (upper Campanian) of Western Canada. Mojoceratops perifania is represented by a skull and a parietal from the Dinosaur Park Formation of Alberta and an isolated parietal from the Dinosaur Park Formation of Saskatchewan.

Several other specimens are provisionally referred to this taxon. While Mojoceratops shares many plesiomorphies with Chasmosaurus, the animal lacks the forward-curving parietal epoccipitals and reduced postorbital horns that diagnose the genus Chasmosaurus, and it differs from all other chasmosaurines in exhibiting a prominent sulcus on the anterior margin of the parietal, swellings on the anterodorsal surface of the parietal rami, and a small accessory process on the first parietal epoccipital. Other unusual features include anteriorly extended parietal fenestrae, a broad, heart-shaped frill, and transverse expansion of the postfrontal fontanelle.

The type material of ‘‘Eoceratops canadensis’’ and ‘‘Chasmosaurus kaiseni’ are nondiagnostic and these names are therefore considered nomina dubia, but their morphology is consistent with Mojoceratops and they probably belong to this genus. The frill of Mojoceratops shows marked variation. Some of this variation probably results from intraspecific variation or ontogenetic changes, but because the Dinosaur Park Formation encompasses more than a million years of time, evolution may explain some of these differences. Phylogenetic analysis shows that Mojoceratops forms a clade with Agujaceratops mariscalensis; Chasmosaurus is the most basal member of Chasmosaurinae.

Holotype

TMP 1983.25.1, a partial skull missing the rostrum, part of the left parietal, and the right side of the face.

Etymology: From mojo (early 20th century African-American English) a magic charm or talisman, often used to attract members of the opposite sex (in reference to the elaborate frill, which may have functioned in courtship), ceras (Greek) horn, and ops (Greek), face. - Perifania (Greek), pride, in reference to the elaborate and erect parietosquamosal frill.

Referred specimens

TMP 1999.55.292, parietal ramus, NMC 8803, partial parietals.

Provisionally referred specimens

AMNH 5656, partial subadult(?) skull missing rostrum and skull roof; AMNH 5401 (Brown, 1933), skull missing posterior margin of the frill (holotype of ‘‘Chasmosaurus kaiseni’’); NMC 1254 (Lambe, 1904, 1915), partial juvenile skull and vertebra (holotype of ‘‘Eoceratops canadensis’’) NMC 34893, partial skull consisting of the skull roof, postorbital horns, and squamosals; TMP 1979.11.147, partial skull consisting of nasals, roof of braincase, supraorbital horncores, exoccipitals, and occipital condyle.

Horizon and locality

Lower and middle Dinosaur Park Formation, Western Canada. NMC 8803 was collected from a bonebed along the South Saskatchewan River (now Lake Diefenbaker). The bonebed lies below the Bearpaw Shale in the Dinosaur Park Formation. These strata correspond to the middle Dinosaur Park Formation exposures in Dinosaur Provincial Park (Tokaryk, personal commun. 2009; Eberth personal commun. 2009), making the specimen approximately 75 million years old (Eberth, 2005). TMP 1979.11.147 was collected from Bonebed 43, a bonebed dominated by Centrosaurus apertus Lambe, 1904 that is located low in the Dinosaur Park Formation in Dinosaur Provincial Park.

This bonebed is located 10.5 m above the contact between the Dinosaur Park Formation and the underlying Oldman Formation (Eberth and Getty, 2005). The remaining specimens were collected in or near Dinosaur Provincial Park, in southern Alberta. TMP 1999.55.292 was collected in the park, from exposures of the Dinosaur Park Formation, but more precise provenance data are not available.

AMNH 5656 was collected by Charles H. Sternberg from the vicinity of Sand Creek. Locality and stratigraphic data are unavailable; however, it is highly probable that the specimen comes from the lower Dinosaur Park Formation, given that the chocolate-brown bone and the clean, bluegrey sandstone matrix associated with the specimen are typical of the lower Dinosaur Park Formation,the Dinosaur Park Formation is far more extensively exposed and more fossiliferous than the underlying Oldman Formation, and most of Sternberg’s other specimens were collected from the Dinosaur Park Formation, suggesting that he targeted this level. NMC 34893 was collected approximately 1 mile southeast of the ghost town of Steveville, placing it in the vicinity of Dinosaur Provincial Park.

The precise locality is not known, but again, the preservation and matrix suggest that it comes from the Dinosaur Park Formation. The most nearly complete specimen, TMP 1983.25.1, was collected by amateurs prior to the passage of Alberta’s fossil Alberta’s Heritage Act and later acquired by the Tyrrell Museum of Paleontology. Unfortunately, due to the circumstances of this specimen’s collection, no provenance data are available. However, it is probable that the skull comes from the Dinosaur Park Formation, rather than the poorly exposed and fossil-poor Oldman Formation.

Diagnosis

Chasmosaurine ceratopsid characterized by the following characters: (1) lateral rami of the parietal posterior bar bearing a prominent sulcus on their anterior surface, (2) lateral rami of the parietal posterior bar with a thickened anterodorsal edge, bearing node-like swellings, (3) parietal epoccipital 1 bearing a medial accessory process, (4) lateral rami of the parietal posterior bar anteroposteriorly narrow and dorsoventrally thickened, giving them a rod-like shape, (5) a strongly notched caudal margin of the parietals, with the lateral rami diverging at an angle of no more than 105u, (6) strongly arched lateral rami of the parietal posterior bar, giving the posterior bar a distinctive ‘m’ shape, and extending the parietals well beyond the squamosals, (7) parietal epoccipitals project caudally from the parietal ( 8 ) parietosquamosal frill erect, long axis of the parietal forming an angle of about 45u with horizontal, (9) parietal fenestrae anteriorly extended towards the supratemporal fossae to a degree not seen in Chasmosaurus, (10) triangular postfrontal fontantelle with strong transverse expansion, (11) prominent supraorbital horns, length exceeding 200% of basal diameter, (12) supraorbital horns oriented dorsolaterally, being inclined away from the vertical plane by 45u in anterior view, (13) epijugal ossification prominent and subconical.

Characters 1– 3 are autapomorphies Mojoceratops, characters 4 and perhaps 9 are derived characters unique to Mojoceratops and Agujaceratops . Characters 1–13 distinguish Mojoceratops from the co-occurring Chasmosaurus. Agujaceratops can be differentiated from Mojoceratops by the absence of characters 1–3, by the erect supraorbital horncores, by the fan-shaped squamosal, by the high number of squamosal epoccipitals (up to 10) (Forster, et al., 1993) and by the elongate squamosal epoccipitals (Lehman, 1989).

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