Crittendenceratops krzyzanowskii gen. & sp. nov.
Sebastian G. Dalman, John-Paul M. Hodnett, Asher J. Lichtig and Spencer G. Lucas (2018)
A new ceratopsid dinosaur (Centrosaurinae: Nasutoceratopsini) from the fort Crittenden Formation, Upper Cretaceous (Campanian) of Arizona.
Lucas, S.G. and Sullivan, R.M., eds., 2018, Fossil Record 6. New Mexico Museum of Natural History and Science Bulletin 791: 141-164
A new ceratopsid dinosaur, Crittendenceratops krzyzanowskii, is described from the Fort Crittenden Formation (Upper Cretaceous) of southeastern Arizona, and is based on two individuals consisting of partial cranial material recovered from the same stratigraphic unit. A phylogenetic analysis of ceratopsids recovers Crittendenceratops as a member of Nasutoceratopsini, a subclade of Centrosaurinae defined as the stem-based clade of centrosaurine ceratopsids more closely related to Avaceratops lammersi and Nasutoceratops titusi than to Centrosaurus apertus. Reconstruction of the parietosquamosal frill based on two specimens indicates that C. krzyzanowskii is a unique, nasutoceratopsin taxon. The parietosquamosal frill of C. krzyzanowskii had a broad medial ramus and at least ïve epiparietal loci situated around the margin of the frill, a typical characteristic of Centrosaurinae. The epiparietals are pronounced triangles that are dorsally concave and ventrally convex. Additionally, two large, triangular hook-like flanges, nearly the size of the epiparietal loci, are situated along the dorsomedial margin of the parietal ramus. The left squamosal has a pronounced dorsal ridge with a single dorsal squamosal process and large episquamosal undulations, a typical characteristic of Centrosaurinae. The presence of C. krzyzanowskii in Arizona indicates that the nasutoceratopsins persisted into the late Campanian. The temporal and paleobiogeographic distribution of Nasutoceratopsini further weakens the hypothesis of distinct northern and southern Laramidian provinces.Â