Abstract

Tanystropheidae is a clade of early archosauromorphs with high morphological disparity and a wide geographicaldistribution. The origin and early radiation of Tanystropheidae are still incompletely understood. Here we reportLuxisaurus terrestrisgen. et sp. nov., a new archosauromorph collected from the marine Upper Member of GuanlingFormation (Pelsonian substage, Anisian, Middle Triassic) in Luxi County, Yunnan Province, China, andphylogenetically recovered as a tanystropheid. The morphology ofLuxisaurusis consistent with a terrestrial lifestyle.This is the first occurrence of a tanystropheid found from the Anisian Guanling Formation in SW China and also theearliest tanystropheid from the eastern Tethys. Phylogenetic analysis shows that Dinocephalosauridae forms the sistergroup of Tanystropheidae,Fuyuansaurusoccupies the most basal position in Tanystropheidae, andLuxisaurusforms thesister group to a clade consisting of all other tanystropheids. Considering thatFuyuansaurusandLuxisaurusare foundexclusively in South China, we hypothesize that Tanystropheidae originated in the Early Triassic of South China andthen dispersed globally. The discovery of Early Triassic tanystropheids in South China is needed to further support thishypothesis. The discovery ofLuxisaurusexpands the stratigraphical and geographical distribution of Tanystropheidae,and provides new insights into the origin and early radiation of the clade.