Redescription Of A Specimen Of Pentaceratops (Ornithischia: Ceratopsidae) And Phylogenetic Evaluation Of Five Referred Specimens From The Upper Cretaceous Of New Mexico

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Fry, Joshua J.
Pentaceratops sternbergi; Ceratopsian anatomy; Ceratopsian evolution; New Mexico ceratopsians; Museum of Northern Arizona; Earth Sciences; Geology; Physical Sciences and Mathematics
thesis / dissertation description
Pentaceratops sternbergi is a late Campanian ceratopsian predominately known from the San Juan Basin in New Mexico. Previous specimen descriptions and cladistic analyses are based on partial skulls and composite specimens, which places Pentaceratops as an intermediate form between Chasmosaurus and Triceratops. Recent reports have questioned the taxonomic validity of several referred specimens, leading to taxonomic confusion. To address taxonomic issues, Museum of Northern Arizona specimen MNA V1747 (formerly MNA Pl. 1747) is redescribed and included in the first specimen-based phylogenetic analysis. Additional preparation since the initial description has made available additional skull elements and revealed MNA V1747 to be the most complete P. sternbergi skull known. Additionally, this study codes five referred specimens as distinct operational taxonomic units (OTU), then added them to previously published ceratopsian phylogenetic matrices for evaluation. Two consensus trees are produced; a tree comparing the five specimens to the OTU assigned to P. sternbergi in recent phylogenetic studies of Ceratopsia and a tree without the P. sternbergi OTU. Results indicate that not all specimens included in this analysis can be confidently assigned to Pentaceratops, suggesting the possibility of misidentified ceratopsian specimens from the San Juan Basin.