Late Pleistocene Mammal Fauna From Mocun Cave,Pubei,Guangxi

The correlational researches of "Ailuropoda-Stegodon" fauna in Southern China has been attractive to scholars.According to the evolutionary traits of Quaternary mammals,they were divided into different mammalian faunas by the early scholars,relatively corresponding to three geologic periods:Early Pleistocene,Middle Pleistocene and Late Pleistocene.The temporal changes of the fauna since Early Pleistocene are as follows:gradual extinction of ancient species and increase of extant ones lead to the distinguish combination of mammalian assemWage;different patterns of body size changing indicate complicated adaptive evolution.Due to the limitation of isotopic dating,the transition between Middle Pleistocene and Late Pleistocene is still Wurred.Meanwhile,in biogeography,"Ailuropoda-Stegodon" fauna spread south to Southeast mainland Asia from Middle Pleistocene producing influence on mammal evolution.So far,reports on the mammalian fauna from Southern China have focused on studies of chronological sequence,lacking of horizontal comparison with Southeast Asia,the connection and interaction are not much discussed.Since the beginning of this century,researchers have carried out a lot of work in Bubing Basin and Chongzuo of Guangxi and made a series of important progress.Quaternary mammal fossil sites in Southern China are so far mainly concentrated in karst areas in northwest and southwest Guangxi.As southeast Guangxi is dominated by plains and hills and scattered with lower karstic peaks in the end of karst process,the mammalian fauna of this area has not been well understood.Although the Quaternary mammalian fauna has long been studied in southern China,there are still many academic proWems to be solved,such as the time nodes of species extinction and emergence,the laws and causes of evolution,the estaWishment of accurate chronological framework,the process of climate and environmental change,etc.This paper reports a new discovery of mammal fauna recovered at Mocun cave in 2000.The Mocun site is located at southeast of a residual karst peak in southwest Guangxi,southern China,which were partly destroyed before discovered.However,abundant mammalian fossil teeth and bones are still stratigraphically restrained within relatively well-preserved,thick and sequential deposits.Based on taxonomic identification,biostratigraphic and isotopic chronology analysis,taphonomy observation,palaeoecological environment analysis and fauna comparison,the following conclusions are obtained:1)the Mocun fauna composed of typical species of "Ailuropoda-Stegodon fauna association",such as extinct species of Stegodon,Ailuropoda,Rhinoceros,Megatapirus,Pongo,co-existing with larger portion of modern species;2)employing U-series dating(MC-ICP-MS)of the soda straw stalactites and mammalian teeth collected from deposits,the age of the Mocun fauna is constrained between 66 and 101 ka,a transitional period from last interglacial to last glacial,corresponding to marine oxygen-isotope stages 4-5(MIS 4-5).It represents one of the most accurately dated fossil sites of late Pleistocene in southern China so far;3)the large mammal assemWage suggests a mosaic environment in hilly plain,which is dominated by forest-dependent species and contains Crocuta ultima of open environment as well;4)taphonomic analysis indicate that the fossil accumulation is mainly due to activities of porcupines and water flows;5)interestingly,our taxonomic study find that Tapirus sinensis was replaced by Megatapirus augustus between～66 and～86 Ka,meanwhile,the varity and quantity of Primates declined sharply and Artiodactyla flourished rapidly.These regional evolutionary events perhaps related to the global climatic transition during the MIS 4-5.