Anatomy of the Late Triassic dinosauromorphs from the Dockum Group of Texas: Their biostratigraphic, paleobiogeographic and evolutionary significance
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The richer and taxonomically more diverse dinosauromorph fauna of the Dockum Group, as comprehensively documented for the first time in the present work, provided new insights on the Late Triassic land vertebrate biochronology and paleobiogeography, especially for the late Carnian-early Norian interval. Although the most recent geochronologic works now enables for a recalibration of the Late Triassic phytosaur biochronology relative to the marine sequence, a direct correlation with South America is still lacking. In this context, the dinosauromorphs are proposed here as a prospecting biostratigraphic tool to correlate North America with South America. Especially, the first appearance of dinosaurs and their early global radiation at the late Carnian-early Norian interval provides a direct correlation with the Paleorhinus Fauna in northern continents (and India) and the Hyperodapedon Acme Zone in southern continents. Conclusive evidences in both northern and southern continents manifest that the occurrence of earliest dinosaurs was global even from the beginning. Ischigualasto and Tecovas formations are the primary candidates to pinpoint the center of origin for dinosaurs by keeping each step of the dinosauromorph evolution, in accord with the new alignment which considers the lagerpetids as the basal taxon of the dinosauromorph clade and the silesaurids as the sister group of dinosaurs.