Xilousuchus

Xilousuchus is a genus of poposauroid from lower Triassic (Olenekian stage) deposits of Fugu County of northeastern Shanxi Province, China. It is known from the holotype, IVPP V 6026, a single well-preserved partial skeletonincluding the skull. It was found from the Heshanggou Formation of the Ordos Basin, Hazhen commune. It was first named by Xiao-Chun Wu in 1981 and the type species is Xilousuchus sapingensis.[1] Wu (1981) referred Xilousuchus to the Proterosuchia. Gower and Sennikov (1996) found it to be an erythrosuchian based strictly on the braincase.[2] A more detailed re-description of the genus was provided by Nesbitt et al. (2010) and found poposauroid affinities.[3] In his massive revision of archosaurs which included a large cladistic analysis, Sterling J. Nesbitt (2011) found Xilousuchus to be a poposauroid which is most closely related to Arizonasaurus.[4] Xilousuchus is the oldest archosaur to date,[4] although Ctenosauriscus and Vytshegdosuchus might be even older by less than one million year.[5] Since Xilousuchus is a suchianarchosaur, its early age suggests that most of the major groups of archosaurs (ornithodirans, ornithosuchids, aetosaurs, and paracrocodylomorphs) developed by the Early Triassic, soon after the appearance of the first archosaur.[3][4]