Dollman, Kathleen N.Clark, James Matthew, 1956-Norell, Mark.Xu, Xing, 1969-Choiniere, Jonah N.Mongolian-American Museum Paleontological Project.Mongolyn Shinzhlėkh Ukhaany Akademi.2018-06-192018-06-192018-06-18http://digitallibrary.amnh.org/handle/2246/689623 pages : illustrations (some color), color map ; 26 cm.Shartegosuchids are a poorly known, early-branching group of Asian and North American crocodylomorphs. Shartegosuchids have been hypothesized to have eusuchian-type secondary palates, but a paucity of described material makes assessing this difficult. Our fieldwork in western Mongolia recovered cranial material of a new Shartegosuchus specimen from the Ulan Malgait Formation, which we CT-scanned and digitally reconstructed to investigate its palatal morphology. We then incorporated this new anatomical information into a revised phylogenetic dataset to assess its affinities. Our study confirms that Shartegosuchus has a posteriorly placed choana that is fully enclosed by the pterygoids, but differs from Eusuchia in possessing a secondary palatal fenestra and reduced palatine bones. Shartegosuchus, together with Adzhosuchus, Fruitachampsa, and Nominosuchus, forms the monophyletic group Shartegosuchidae. Shartegosuchidae is nested within a larger clade Shartegosuchoidea, and this clade is an earlier-diverging lineage than Eusuchia, showing that a eusuchian-type secondary palate evolved multiple times in crocodylomorphs, including very early in the group's evolutionary history. The co-occurrence of Nominosuchus in the Ulan Malgait Formation and the Shishigou Formation allows us to assign an early Oxfordian age to Shartegosuchus. The independent evolution of a eusuchian-type secondary palate in an oreinorostral group suggests that the link between platyrostry and a closed secondary palate has been overstated.en-USShartegosuchus asperopalatum.Palate.Nasal fossa.Convergence (Biology)Shartegosuchidae.Shartegosuchoidea.Phylogeny.Crocodylomorpha.Crocodilians.Govʹ-Altaĭ Aĭmag (Mongolia)Mongolia.