Chronological sequence of the early Pleistocene Gigantopithecus faunas from cave sites in the Chongzuo, Zuojiang River area, South China

Since 2004, five new early Pleistocene cave sites with Gigantopithecus blacki and other fossil mammals have been discovered in the Chongzuo, Zuojiang River area, Guangxi Zhuang Autonomous Region (Guangxi ZAR), South China. These sites include Baikong Cave of Liyu Mountain, Juyuan Cave of Boyue Mountain, Sanhe and Queque Caves of Wuming Mountain, and Wuming Cave of Mulan Mountain. The present study provides a preliminary account of these newly discovered Gigantopithecus faunas, and discusses their taxonomic composition, evolutionary trends and chronology based on recent biostratigraphic and geochronological studies. Combining faunal and paleomagnetic data, the Gigantopithecus faunas from the Zuojiang River area can be divided into three temporal stages during the early Pleistocene. The early stage (2.6-1.8Ma) is represented by the Baikong and Boyue faunas, which include some Neogene relics (e.g., Sinomastodon, Hesperotherium, Dicoryphochoerus, Dorcabune and Cervavitus) and several species that make their first appearance during the Pleistocene (e.g., Sinicuon dubius, Pachycrocuta licenti, Ailuropoda microta, Sinomastodon jiangnanensis, Stegodon huananensis and Tapirus sanyuanensis). The middle stage (1.8-1.2Ma) is represented by the Sanhe fauna, which is characterized by the appearance of Ailuropoda wulingshanensis, Cuon antiquus, and Tapirus sinensis. The late stage (1.2-0.8Ma) is represented by the Queque fauna, which is characterized by a marked decrease in Neogene relics and the appearance of a few species that are more typical of the middle Pleistocene (e.g., Ailuropoda baconi and Stegodon orientalis). Evolutionary trends in the early Pleistocene Gigantopithecus faunas include a gradual increase in dental size in some of the typical taxa, such as G. blacki, Ailuropoda and Tapirus, and the successive turnover of representative species, such as A. microta - A. wulingshanensis - A. baconi. Thus far, Eleven G. blacki sites of early Pleistocene age have been recorded in southern China, and these are primarily concentrated in Guangxi ZAR, where more than 70% of early Pleistocene G.blacki cave sites are known. Given this temporal and geographic distribution it is possible to infer that Guangxi ZAR represents an important early evolutionary and zoogeographic center for G.blacki.