[D] Chasmosaurus mariscalensis [Su]
Cretaceous Late Maastrichtian
Ornithischia Genasauria Cerapoda Marginocephalia Ceratopia Neoceratopia Ceratopidae Chasmosaurinae
Aguja Formation, Texas, US; Mexico
Agujaceratops mariscalensis (Lucas, Sullivan & Hunt, 2006) > Chasmosaurus mariscalensis (Lehman, 1989)
12 disarticulated skull, postcrania, juvenile The diagnostic features of Chasmosaurus mariscalensis include an extensive anteromedial projection of the nasal between the premaxillae, erect supraorbital horns, and laterally rounded squamosal. Nine cranial features that vary among Chasmosaurus species, Pentaceratops sternbergii, and other chasmosaurines are analyzed. Chasmosaurus mariscalensis appears to be most closely related to northern species of (Chasmosaurus belli, Chasmosaurus russelli), which also exhibit a transversely flattened nasal horn and modifications of the anterior margin of the external naris.
The genus Chasmosaurus, in turn, appears to be most closely related to the other southern chasmosaurine, Pentaceratops sternbergii. The biogeographic history inferred from these relationships suggest that the biogeographic exchange between northern and southern chasmosaurines that must have occurred cannot be explained by a single dispersal event to the south.