A new kannemeyeriiform dicynodont (Synapsida) from a Late Triassic vertebrate assemblage in west Texas, U.S.A.Citation for this article: Mueller, B. D., Huttenlocker, A. K., Small, B. J., Pinto, J. L., Dean-Wallace, K., & Chatterjee, S. (2023) A new kannemeyeriiform dicynodont (Synapsida) from a Late Triassic vertebrate assemblage in west Texas, U.S.A. Journal of Vertebrate Paleontology . https://doi.org/10.1080/02724634.2023.2255236

Abstract

ABSTRACTA new kannemeyeriiform dicynodont is described from the Upper Triassic Tecovas Formation (Dockum Group) of west Texas, U.S.A. The taxon, Argodicynodon boreni gen. et sp. nov., is diagnosed by numerous cranial characters including: squamosal-interparietal sutural contact broad and interdigitating; tall, narrow intertemporal region formed by the parietals with long postorbitals forming the lateral face of the dorsal platform; interparietal forms knobby, bilobed exostoses that wedge between the parietals to form a W-shaped outline in dorsal view; basioccipital and exoccipital contributions to the occipital condyle are distinct, and the dorsal fossa separating the exoccipitals is deeply incised and dorsoventrally deep; caniniform process of the maxilla is dorsoventrally deep and well developed; and an elongated tab-like medial process of the articular exceeds the width of the quadrate roller. A phylogenetic analysis based on 23 continuous and 176 discrete (numeric) morphological characters and 120 taxa finds Argodicynodon conservatively to be a placeriine near the Placerias + Moghreberia group, representing the oldest placeriine in the southwestern U.S.A. and the first named dicynodont genus from the Dockum Group of Texas. A review of Euramerican dicynodont records exposes their hidden diversity and abundance in Laurasia during the Late Triassic. The records of Argodicynodon and other previously undescribed dicynodont fossils from nearby localities underscores the diversity of non-Placerias dicynodonts in the North American Upper Triassic.http://zoobank.org/urn:lsid:zoobank.org:pub:AB9B7ABC-6C84-4B04-909F-F1DA114030AB ACKNOWLEDGMENTSThis study is based in part on the dissertation of BDM under the guidance of his committee members SC, J. Barrick, and T. Lehman. We thank J. Boren and the Boren family for granting access to the site and the generous donation of the fossil material to the Museum of Texas Tech University. We thank the numerous Texas Tech students and volunteers who assisted in the field and lab. B. Meyers is acknowledged for discovery of the locality MOTT VPL 3881 and the left humerus (TTU-P10421). We also thank P. Holroyd and the UCMP for access to comparative material from the Placerias quarry. Special thanks to D. Cunningham, G. Gürtler, A. Hungerbühler, J. Martz, S. Nesbitt, and W. Parker for assistance in various aspects of this project. We also thank K. Angielczyk, C. Kammerer, and T. Sulej for their helpful feedback on our manuscript. This project was made possible through the support of the Museum of Texas Tech University.DISCLOSURE STATEMENTNo potential conflict of interest was reported by the author(s).AUTHOR CONTRIBUTIONSBDM designed the project and wrote sections for the initial draft as part of his unpublished doctoral dissertation. AKH and BJS collected data, revised and edited the manuscript, drafted and revised the figures, and performed the phylogenetic analyses. AKH and JLP collected additional comparative data and photographs from Placerias. KD-W and SC provided additional data and photographs. All authors edited the manuscript.SUPPLEMENTARY FILESSupplementary Data 1: Detailed methods (supplementary Appendices S1–S5).Supplementary Data 2: NEXUS-formatted file for cladistic analysis (complete dataset).Supplementary Data 3: NEXUS-formatted file for cladistic analysis (pruned kannemeyeriiform dataset).Supplementary Data 4: TNT-formatted file of complete analysis.Supplementary Data 5: TNT-formatted file of reduced analysis.