A New Eosauropterygian (Diapsida, Sauropterygia) from the Triassic of China

A new Middle Triassic sauropterygian, Qianxisaurus chajiangensis, gen. et sp. nov., is described on the basis of a skeleton from the Zhuganpo Member (Ladinian) of the Falang Formation, Xingyi, southwestern Guizhou Province, China. It is primarily characterized by a premaxilla with eight teeth, marginal teeth with a slightly constricted peduncle and short conical crown, snout longer than the rest of skull, postorbital with a truncated dorsal process and forked posterior process, a very small supratemporal fenestra, a short retroarticular process posteriorly truncated and lacking a dorsal concavity, an elongate trunk with 28 vertebrae, a stout sacrum with four vertebrae, a longitudinal groove on proximodorsal surface of the dorsal ribs, and a coracoid with a narrow lateral portion and a foot-shaped medial portion. Q. chajiangensis appears similar to the European pachypleurosaurs, but a global phylogenetic analysis failed to support close relationships with these taxa. Instead, Q. chajiangensis is an eosauropterygian and most probably the sister group of a clade consisting of the European pachypleurosaurs and the Nothosauroidea. The discovery of Q. chajiangensis certainly enriches our knowledge of the early history of the Eosauropterygia and leads to a better understanding of the phylogenetic relationships among known eosauropterygians.