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.2013.[J].Acta Geologica Sinica(),87(3):672-677
A New Triassic Primitive Ichthyosaur from Yuanan, South ChinaDownload PDF
CHEN Xiaohong, P. Martin SANDER, CHENG Long and WANG Xiaofeng
1 Wuhan Centre of China Geological Survey, Wuhan 430223, China
2 Steinmann-Institut für Geologie, Mineralogie und Pal?ontologie, Universit?t Bonn, Nussallee 8, D-53115 Bonn, Germany
This study was supported by the China Geological Survey (Grant No. 1212010611603 and 1212011120148).
Based on the systematic study of two fossil skeleton specimens collected from the top of the third member of the marine Lower Triassic Jialingjiang Formation of Yuanan, Hubei Province, South China, a new Early Triassic primitive ichthyosaur Chaohusaurus zhangjiawanensis sp. nov. is reported and described. The beds yielding the type material are correlated with the Neospathodus homeri–N. triangularis Conodont zone. The new taxon is most similar to Chaohusaurus geishanensis Young and Dong, 1972 in the shape and configuration of the scapula, forefin, pelvic girdle and hindfin, presacral vertebral count and well-developed caudal peak, but distinguished from the latter by its larger size, the position of the pineal foramen in the centre of the parietal, the occurrence of a larger calcaneum in hindfin and the first sacral rib with distal expansion. The new species exhibits common features of primitive ichthyosaurs such as: (1) the prefrontal has an antero-dorsal shelf projecting towards the orbit; (2) the upper temporal fenestra is small; (3) the postorbital and the squamosal meet laterally to the upper temporal fenestra; and (4) cylindrical centra. However, more derived ichthyosaur characters are seen with the frontal separated from the orbital dorsal margin by the contact of the prefrontal and postfrontal, which offer new clues to the early radiation of ichthyosaurs.