Largocephalosaurus

Largocephalosaurus is an extinct genus of basal saurosphargid, a marine reptile known from the Middle Triassic (Anisian age) Guanling Formation of Yunnan and Guizhou Provinces, southwestern China. It contains a type species, Largocephalosaurus polycarpon, and a second species L. qianensis.

L. polycarpon was initially interpreted as an eosauropterygian sauropterygian closely related to European pachypleurosaurs and nothosaurids. However following additional preparation of the postcranial skeleton and the discovery of a second better known species L. qianensis, Li et al. (2014) reinterpreted Largocephalosaurus as a basal member of the family Saurosphargidae and a close relative of Saurosphargis and Sinosaurosphargis. According to Li et al. (2014), saurosphargids did not belong to Sauropterygia, although they were closely related to it, forming its sister taxon.

Discovery

The type species of Largocephalosaurus, L. polycarpon is known only from the holotype WIGM SPC V 1009 a nearly complete and articulated skull and skeleton missing most of its tail and measuring more than 113 centimetres (3.71 ft) in length, housed at the Wuhan Institute of Geology and Mineral Recourses. SPC V 1009 was collected from Member II of the Guanling Formation, dating to the Pelsonian substage of the mid-late Anisian stage of the early Middle Triassic, about 243 million years ago, at Luoping County of Yunnan Province.

While L. polycarpon was being studied at the WIGM, three specimens of what was later named L. qianensis were prepared at the Geological Museum of Peking University and the Institute of Vertebrate Paleontology and Paleoanthropology.