Systematics of new information from the Chasmosaurus - Peabody Museum skull , and the use of phylogenetic analysis for dinosaur alpha taxonomy

The horned dinosaur from the late Campanian Dinosaur Park Chasmosaurus Formation of Alberta, is known from numerous skulls and skeletons, but over a century after its description, the taxonomy of the genus is controversial. Two species, and , are currently recognized, with a Chasmosaurus belli C. russelli third species, , recently placed in a new genus, . C. irvinensis Vagaceratops Here, the Yale skull is described, and implications for Chasmosaurus systematics are explored. The Yale skull is intermediate Chasmosaurus between typical and . -like features include large, C. belli C. irvinensis C. belli triangular lateral epiparietals, large parietal fenestrae, and an emarginate parietal. Yet the skull also exhibits derived features of , including a C. irvinensis posteriorly inclined narial strut, brow horns replaced by rugose bosses, reduced parietal emargination, five pairs of epiparietals, and epiparietals that fuse at their bases and hook forward over the frill. Specimen-level phylogenetic analysis provides a hypothesis of relationships upon which to base the taxonomy of . is paraphyletic with respect to Chasmosaurus C. belli C. irvinensis , and the Peabody skull is closer to than to other . The C. irvinensis C. belli holotype of clusters with , making a junior synonym C. russelli C. belli C. russelli of . . Accordingly, can be divided into three species: C belli Chasmosaurus C. , , and sp. nov, including specimens previously belli C. irvinensis C. priscus referred to . . The systematics of show how specimen C russelli Chasmosaurus level phylogeny can provide an evolutionary framework upon which to establish taxonomies. However, the resulting phylogenies may lead to paraphyletic species and genera. Nicholas Longrich ( ) Corresponding author: [email protected] Longrich N. How to cite this article: Systematics of new information from the Peabody Museum skull, and the use of Chasmosaurus 2015, :1468 (doi: phylogenetic analysis for dinosaur alpha taxonomy [version 1; referees: 1 not approved] F1000Research 4 ) 10.12688/f1000research.7573.1 © 2015 Longrich N. This is an open access article distributed under the terms of the , which Copyright: Creative Commons Attribution Licence permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. NRL was funded by a Donnelley Postdoctoral Fellowship and the Yale Institute for Biospheric Studies. Grant information: The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: No competing interests. 17 Dec 2015, :1468 (doi: ) First published: 4 10.12688/f1000research.7573.1 Referee Status: