Late eocene sivaladapid primate from Guangxi Zhuang Autonomous Region, People's Republic of China

A new genus and species of Sivaladapidae is described from the late Eocene Gongkang Formation, Yongle Basin, western Guangxi Zhuang Autonomous Region, southern China. Guangxilemur tongi, new genus and species, shows a combination of traits that occur separately in earlier and more primitive Asian adapiforms (Hoanghonius and Rencunius) and in Miocene sivaladapines (Sivaladapis and Sinoadapis). Phylogenetic analysis of dental characters suggests that Guangxilemur is closely related to the Miocene sivaladapine clade. Miocene sivaladapines were the latest surviving members of a broad radiation of Eocene adapiforms in Asia that included Hoanghonius, Rencunius, and Wailekia in addition to Guangxilemur. European Periconodon may also be specially related to this primarily Asian clade, but current anatomical data are insufficient to test this possibility adequately. Sivaladapine adapiforms and tarsiid tarsiiforms maintained relictual distributions in southern and/or southeastern Asia far beyond the extirpation of their closest relatives on other Holarctic continents near the Eocene-Oligocene boundary. This temporal persistence was mediated by Asian paleogeography, which allowed virtually continuous access to tropical refugia during a middle Cenozoic interval of climatic deterioration that coincided with the extinction of adapiforms and tarsiiforms in Europe and North America.