Sunday, November 4, 2018

[Paleontology • 2018] Crittendenceratops krzyzanowskii • A New Ceratopsid Dinosaur (Centrosaurinae: Nasutoceratopsini) from the Fort Crittenden Formation, Upper Cretaceous (Campanian) of Arizona

Crittendenceratops krzyzanowskii 
 Dalman, Hodnett, Lichtig & Lucas, 2018

Life reconstruction by Sergey Krasovskiy. 

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 five 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.


CERATOPSIA Marsh, 1890

NASUTOCERATOPSINI Ryan, Holmes, Mallon, Loewen, and Evans, 2017

 Crittendenceratops, new genus

 Etymology: Derived from “Crittenden” referring to the Fort Crittenden Formation, the stratum from which the specimen came; “ceratops,” meaning a “horned-face” in Latinized Greek. 

Crittendenceratops krzyzanowskii, new species

Etymology: The specific epithet honors the late Stan Krzyzanowski, who discovered and collected the specimen.

Diagnosis: Centrosaurine ceratopsid characterized by the following unique combination of characters: forward-curving, hook-like flanges located along the dorsomedial margin of the parietal lateroposterior ramus; extensive epiparietals located along the lateroposterior margin of the parietal ramus; parietal ramus dorsoventrally thick; dorsal surface of the parietal ramus contains deep elongate fossa; posteroventrolateral concavity pronounced and extensively rugose; squamosal dorsal ridge short, pronounced and located in close proximity to dorsolateral margin of the bone.  

Crittendenceratops krzyzanowskii is a new genus and species that represents the youngest current record of nasutoceratopsins in North America. The identity of a new member of the Nasutoceratopsini clade in southern Laramidia fills in the evolutionary gap between the slightly older Yehuecauhceratops and the nasutoceratopsins known from the late Campanian in northwestern North America. Furthermore, Crittendenceratops and Yehuecauhceratops add new information to the paleobiogeographic distribution of nasutoceratopsins during the Cretaceous. 

Life reconstruction of Crittendenceratops krzyzanowskii gen. et sp. nov.

by Sergey Krasovskiy.

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. New Mexico Museum of Natural History and Science Bulletin. 79: 141–164.