Late Triassic dinosauriforms from the Post Quarry and surrounding areas, west Texas, USA

Dinosauriform and dinosaurian remains are rare from the Late Triassic Dockum Group of Texas. Using a synapomorphy-based approach, we evaluate new remains and previously reported remains assigned to Dinosauria from the Post Quarry (Garza County, Texas) and find that that the assemblage contains a non-dinosaur dinosauriform, an early saurischian, and a coelophysoid theropod. A partially associated skeleton of a dinosaur found stratigraphically higher than the Post Quarry has a suite of plesiomorphic states of early saurischians combined with two unambiguous synapomorphies of coelophysoids, indicating that it may be one of the most basal theropods. The dinosaurian assemblage from the Post Quarry confirms the hypothesis that non-dinosaurian dinosauriforms and dinosaurs coexisted both through time and geographically across western North America.