A new tanystropheid (Diapsida: Archosauromorpha) from the Middle Triassic of SW China and the biogeographical origin of Tanystropheidae

AbstractTanystropheidae is a clade of early archosauromorphs with high morphological disparity and a wide geographical distribution. The origin and early radiation of Tanystropheidae are still incompletely understood. Here we report Luxisaurus terrestris gen. et sp. nov., a new archosauromorph collected from the marine Upper Member of Guanling Formation (Pelsonian substage, Anisian, Middle Triassic) in Luxi County, Yunnan Province, China, and phylogenetically recovered as a tanystropheid. The morphology of Luxisaurus is consistent with a terrestrial lifestyle. This is the first occurrence of a tanystropheid found from the Anisian Guanling Formation in SW China and also the earliest tanystropheid from the eastern Tethys. Phylogenetic analysis shows that Dinocephalosauridae forms the sister group of Tanystropheidae, Fuyuansaurus occupies the most basal position in Tanystropheidae, and Luxisaurus forms the sister group to a clade consisting of all other tanystropheids. Considering that Fuyuansaurus and Luxisaurus are found exclusively in South China, we hypothesize that Tanystropheidae originated in the Early Triassic of South China and then dispersed globally. The discovery of Early Triassic tanystropheids in South China is needed to further support this hypothesis. The discovery of Luxisaurus expands the stratigraphical and geographical distribution of Tanystropheidae, and provides new insights into the origin and early radiation of the clade.http://zoobank.org/urn:lsid:zoobank.org:pub:07DE12AC-8AE7-48F0-8BAD-0B73F04C0858Keywords: marine reptileDinocephalosauridaephylogenyGuanling Formation AcknowledgementsWe thank Y. W. Hu, Q. Li, A. S. Wolniewicz and J. He for the discussion of the specimen, other members of the Paleontological Lab of HFUT for their help in the field, T. Sato and L. Y. Li for preparation of the specimen, and S. N. F. Spiekman for help in the phylogenetic analysis. Constructive comments from S. N. F. Spiekman and N. C. Fraser helped improve the manuscript.Supplemental materialSupplemental material for this article can be accessed here: https://doi.org/10.1080/14772019.2023.2250778.Associate Editor: Richard ButlerAdditional informationFundingThis work was supported by the National Natural Science Foundation of China (42172026 and 41772003) and the Department of Natural Resources of Anhui Province (2021-g-2-16).