Dinevenator, a New Genus of Troodontid Dinosaur from the Late Cretaceous of New Mexico

An isolated left frontal from the Upper Cretaceous (upper Campanian) strata of the San Juan Basin in northwestern New Mexico, USA, was originally identified as a species of the dromaeosaurid (Theropoda: Dromaeosauridae) Saurornitholestes (“S.” robustus) and was subsequently identified as a troodontid (Troodontidae). A reassessment of this holotype specimen shows its distinct nature among troodontids and is here named Dinevenator, gen. nov. Dinevenator robustus differs from other troodontids, including the thick-skulled species Xenovenator espinosai from the upper Campanian Cerro del Pueblo Formation, Coahuila, Mexico. These differences include: dorsoventrally thick and robust frontals; frontals thicker posteriorly; relatively flat frontals, lacking a well-developed parasagittal trough and sagittal ridge; a posteromedial nasal projection between the frontals that is wider than long; a more laterally oriented posterior portion of the lateral endocranial wall; and a mediolaterally wider anteromedial portion of the frontal that houses the orbital fossa. A phylogenetic analysis was also run based on a modified dataset, recovering Dinevenator robustus in a clade of robust troodontins (Troodontini) as the basal-most taxon and as the sister taxon to (Albertavenator curriei + Xenovenator espinosai). The recognition of a distinct, large, robust-skulled troodontid also increases the known diversity of theropod dinosaurs from the southern United States and provides further evidence for dinosaurs that are unique to the Kirtlandian faunas of New Mexico during the Late Cretaceous.