New information on Wumengosaurus delicatomandibularis Jiang et al., 2008 (Diapsida: Sauropterygia), with a revision of the osteology and phylogeny of the taxon

ABSTRACT

Wumengosaurus delicatomandibularis Jiang et al., 2008, is restudied on the basis of three new specimens. Many elements of the skeleton that were either briefly or not described at all in the original study are detailed. With the additional information derived from the new specimens, we have revised the diagnosis of W. delicatomandibularis. A phylogenetic analysis further demonstrates that the Pachypleurosauria is not a monophyletic group and questions that W. delicatomandibularis is closely related to the Pachypleurosauria. W. delicatomandibularis might represent the basal-most member of a monophyletic clade that includes the Nothosauroidea and those taxa assigned to the ‘Pachypleurosauria.’ The five known specimens show morphological variation in W. delicatomandibularis, as in Keichousaurus and in pachypleurosaurs such as Neusticosaurus and Serpianosaurus.

ACKNOWLEDGMENTS

We are grateful to Jin-zhao Ding (IVPP), Hong-jiao Zhou (IVPP), and Paleowonder Fossil and Mineral Museum (Taipei) for their skillful preparation of the specimens used in this study and providing generous assistance during this project. We thank His-yin Shan (NMNS) for making the line drawing of the skull of NMNS-KIKO-F071129-Z. Da-yong Jiang and his research crew (Beijing University) graciously permitted XcW to access the holotype and paratype specimens in their care. Olivier Rieppel (Field Museum) and Robert Holmes (University of Alberta) kindly provided the data matrix for the phylogenetic analysis; they, Constanze Bickelmann, and an anonymous reviewer critically reviewed the manuscript. Richard Day of the Canadian Museum of Nature (CMN) read and edited an earlier draft. Editor Sean Modesto provided editorial assistance. X.-c.W. particularly wishes to thank the IVPP and the NMNS for their hospitality during his visits. This work was supported by research grants from the CMN (to X.-c.W.); from the NMNS and the National Science Council, Taiwan (NSC-95-2116-M-178-001) (to Y.-n.C.); from the Major Basic Research Projects (2006CB806400) of the Ministry of Science and Technology of China, the National Natural Science Foundation (NNSFC-40772015, 40121202) of China, and the CAS/SAFEA International Partnership Program for Creative Research Teams (to C.L. and X.-c.W.); and from the ZMNH (to L.-j.Z.); and from Tokyo Gakugei University (to T.S.).

Handling editor: Sean Modesto