A new kannemeyeriiform dicynodont (Synapsida) from a Late Triassic vertebrate assemblage in west Texas, U.S.A.

A new kannemeyeriiform dicynodont is described from the Upper Triassic Tecovas Formation (Dockum Group) of west Texas, U.S.A. The taxon, <i>Argodicynodon boreni</i> 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 <i>Argodicynodon</i> conservatively to be a placeriine near the <i>Placerias</i> + <i>Moghreberia</i> 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 <i>Argodicynodon</i> and other previously undescribed dicynodont fossils from nearby localities underscores the diversity of non-<i>Placerias</i> dicynodonts in the North American Upper Triassic. http://zoobank.org/urn:lsid:zoobank.org:pub:AB9B7ABC-6C84-4B04-909F-F1DA114030AB