2021 as Amphicotylus milesi, in honor of Clifford Miles for his contribution to the excavation and museum curation. DescriptionAmphicotylus had a roughly triangular, platyrostral skull similar in shape to that of modern crocodilians. They differ from European goniopholidids in several morphological characters, most notably the anatomy of the palate. In members of Amphicotylus, the palatines are completely separated from one another by the choana while in Goniopholis the palatines make broad contact prior to the choana. This trait is shared by Eutretauranosuchus. Amphicotylus milesi is the largest species with a skull length of 43 cm. The anatomy of the palate and hyoid in A. milesi show similar adaptations to extant crocodilians, with the anterior portion of the elongated choana possibly being covered in soft tissue similar to the state observed in embryos of American alligators. Based on the morphology of the hyoid apparatus and its muscle attachments, A. milesi would have been able to raise the ventral fold of the gullar valve, separating narial and oral passages. This adaptation for semi-aquatic life would have allowed Amphicotylus and other Neosuchians to completely cut out the oral cavity from respiration, giving it the ability to open its mouth underwater while continuing to breathe as long as the nares are above the surface. This pushes the development of a crocodilian-like respiratory system to the beginnings of Neosuchian evolution in the Jurassic period. Phylogeny Studies have repeatedly found Amphicotylus to be nested deep within Goniopholididae, typically located just outside the clade that contains most European members of the group. Denazinosaurus, a late Cretaceous member of Goniopholididae, was recovered as a sister taxon to Amphicotylus by Puértolas-Pascual et al. 2015, but as part of the "European clade" by Yoshida et al. 2021. Yoshida et al. also include Sunosuchus thailandicus without following the revisions by Martin et al. 2013 that found it to be a distinct genus of pholidosaurid, Chalawan thailandicus. The phylogenetic tree recovered by Yoshida et al.'' is depicted below. References Neosuchians Late Jurassic crocodylomorphs of North America Late Jurassic reptiles of North America Morrison fauna Fossil taxa described in 1878 Taxa named by Edward Drinker Cope Prehistoric pseudosuchian genera