Dispersal of African mammals in Eurasia during the Cenozoic: Ways and whys

Several groups of mammals originated in Africa and then immigrated to Eurasia during some intervals of the Cenozoic, thus greatly contributing to the mammalian biodiversity in Eurasia. Nevertheless, the African components of Eurasian mammalian faunas have had variable success in their diversification and survival. The Afro-Arabian plate remained separated from Eurasia by the Tethyan seaway, which was definitely closed in the Burdigalian, some 20 myr ago. Before its closure, the marine barrier between the Afro-Arabian and Eurasian plates did not totally prevent mammalian exchanges between these landmasses, as documented by the arrival of rodents and primates in Africa in the late Paleocene-early Eocene, the dispersal of embrithopods on both sides of the Tethyan seaway during the Eocene, and the immigration of elephantoids from Africa to Asia in late Oligocene. These events seem to be restricted to some groups of mammals, which apparently had abilities to use sweepstake dispersal routes. The massive mammalian dispersal from Africa to Eurasia started sometimes in the early Miocene, involving several groups of African mammals, in particular proboscideans, hyracoids, tubulidentates, and anthropoids. This contribution discusses the timing of these events under the light of recent discoveries of Africa-originated mammals in Eurasia. The impact of the evolving paleogeography of the area situated between the Afro-Arabian and Eurasian plates on the mammalian dispersal is reconsidered. The dispersal of land mammals from Africa to Eurasia is controlled not only by the paleogeographic changes (sea level changes, dispersal routes, terrestrial bridges, etc.), but also by climatic factors that modified the environments of terrestrial mammals, favoring or not the occurrence of dispersal routes and/or the enlargement or restriction of climatic belts and biogeographic provinces to which these mammals were adapted. These questions are discussed taking into account the present knowledge of the record of the Africa-originated mammals in Eurasia during the Cenozoic times.