title: A new rauisuchid (Archosauria, Pseudosuchia) from the Upper Triassic (Norian) of New Mexico increases the diversity and temporal range of the clade.
abstract: Rauisuchids are large (2-6 m in length), carnivorous, and quadrupedal pseudosuchian archosaurs closely related to crocodylomorphs. Though geographically widespread, fossils of this clade are relatively rare in Late Triassic assemblages. The middle Norian (∼212 Ma) Hayden Quarry of northern New Mexico, USA, in the Petrified Forest Member of the Chinle Formation, has yielded isolated postcranial elements and associated skull elements of a new species of rauisuchid. Vivaron haydeni gen. et. sp. nov. is diagnosed by the presence of two posteriorly directed prongs at the posterior end of the maxilla for articulation with the jugal. The holotype maxilla and referred elements are similar to those of the rauisuchid Postosuchus kirkpatricki from the southwestern United States, but V. haydeni shares several maxillary apomorphies (e.g., a distinct dropoff to the antorbital fossa that is not a ridge, a straight ventral margin, and a well defined dental groove) with the rauisuchid Teratosaurus suevicus from the Norian of Germany. Despite their geographic separation, this morphological evidence implies a close phylogenetic relationship between V. haydeni and T. suevicus. The morphology preserved in the new Hayden Quarry rauisuchid V. haydeni supports previously proposed and new synapomorphies for nodes within Rauisuchidae. The discovery of Vivaron haydeni reveals an increased range of morphological disparity for rauisuchids from the low-paleolatitude Chinle Formation and a clear biogeographic connection with high paleolatitude Pangea.
authors.affiliation: Department of Geosciences, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, United States; Department of Biological Sciences, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, United States.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Lessner
authors.affiliation: Department of Geosciences, Virginia Polytechnic Institute and State University (Virginia Tech) , Blacksburg, VA , United States.
authors.forename: Michelle R
authors.identifier: 0000-0002-6473-8691
authors.initials: MR
authors.lastname: Stocker
authors.affiliation: The Dinosaur Institute, Natural History Museum of Los Angeles County , Los Angeles, CA , United States.
authors.forename: Nathan D
authors.initials: ND
authors.lastname: Smith
authors.affiliation: Department of Anatomical Sciences, Stony Brook University , Stony Brook, NY , United States.
authors.forename: Alan H
authors.initials: AH
authors.lastname: Turner
authors.affiliation: Natural History Museum of Utah, University of Utah, Salt Lake City, UT, United States; Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, United States.
authors.forename: Randall B
authors.initials: RB
authors.lastname: Irmis
authors.affiliation: Department of Geosciences, Virginia Polytechnic Institute and State University (Virginia Tech) , Blacksburg, VA , United States.
authors.forename: Sterling J
authors.initials: SJ
authors.lastname: Nesbitt
keywords: Hayden Quarry; Postosuchus; Rauisuchidae; Teratosaurus