A late Middle Pleistocene mammalian fauna recovered in northeast Guangxi, southern China: Implications for regional biogeography

摘要

In Guangxi Zhuang Autonomous Region, southern China, Quaternary mammalian assemblages, commonly known as "Stegodon-Ailuropoda fauna", are well documented in the central and southwest parts of the region. Unfortunately, our knowledge of Quaternary biogeographic variation in other areas of Guangxi is poor due to limited systematic investigations. Here, we report the faunal remains from the newly discovered Diaozhongyan ("DZY") cave site in northeast Guangxi. Our initial excavation in autumn 2016 resulted in the removal of 10 square meters of sediment and the discovery of 304 pieces of large mammal teeth. Biostratigraphic correlations indicate a late Middle Pleistocene age and in situ fossil teeth and calcites were Uranium-series dated to similar to 210 ka. The DZY faunal assemblage consists of many typical components of the traditional "Ailuropoda-Stegodon" fauna representative of southern China. Interestingly, giant pandas, identified as Ailuropoda melanoleuca baconi, are one of the dominant components of the DZY fauna (15% of the entire assemblage). However, giant pandas rarely dominate Quaternary faunal assemblages in southern China. In addition, fossil orangutan (Pongo weidenreichi), one of the most common species in central and south Guangxi during the Middle Pleistocene, is absent in DZY in northeast Guangxi. Further, fossil orangutans have not been reported from other sites in Hunan or Hubei pro-vince. We hypothesize that the Nanling Mountains served as a geographic barrier for this species. Fossil orangutans are present southwest of this biogeographic line, but are absent northeast of the line. This biogeographic boundary needs to be further evaluated with additional studies.