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.
We are grateful to Paleowonder Fossil and Mineral Museum (Taipei) for their skillful preparation of the specimens used in this study and for providing generous assistance during this project. X.-C.W. particularly wishes to thank the Department of Geology of NMNS for their hospitality during his visits. R. OâKeefe, J. Liu, and an anonymous colleague reviewed the manuscript, offering critical comments and suggestions that led to its great improvement. This work was supported by research grants from the NMNS and the National Science Council, Taiwan (NSC-95-2116-M-178-001) (to Y.-N.C.), from the CMN (to X.-C.W.), and Tokyo Gakugei University (to T.S.).
Handling editor: Robin OâKeefe