Advance in studies of the Panxian fauna

The Panxian fauna is mainly characterized by well-preserved and articulated skeletons of Middle Triassic (Anisian) marine reptiles with high diversity, associated with abundant invertebrate fossils, such as bivalves, brachiopods as well as cephalopods, and some as yet undescribed taxa. Stratigraphically, it occurred at the Upper Member of the Guanling Formation, ascribed to the conodont Nicoraella kockeli zone, which indicates that the age of this fauna is Pelsonian (Middle Anisian). Therefore, the Panxian fauna is older than the Grenzbitumenzone fauna at Besano/Monte San Giorgio area of Italy/Switzerland border (near Anisian/Ladinian boundary), and represents the oldest marine reptile fauna of the Middle Triassic throughout the world. Such a rich, diversified and perfectly preserved paleontological assemblage with the exact stratigraphic horizon and definitive age not only provides abundant materials for exploring the taxonomy, evolution, and origin of the marine reptiles, but also has great significance for developing the study of paleoecology and biogeographic provincialism. So far, five genus and five species, including the oldest mixosaurid ichthyosaurs, the oldest lariosaurs and the first true aquatic protorosaur( Dinocephalosaurus orientalis), have been reported from the Panxian fauna. Most of them are adapted to epicontinental environment or shallow sea, and show a strong West Tethyan affinity. The strata bearing the Panxian fauna consists of four or five tuff beds and seven volcanicities were recognized, which might be caused by the extinction of these marine reptile animals directly.EI06817-8234