Afrotherian mammals: a review of current data

Abstract

The supraordinal mammalian clade Afrotheria was first recognized in its entirety based on DNA analysis dating to the mid-1990s. Since then, this “African clade”, which includes proboscideans, sirenians, hyracoids, tubulidentates, elephant-shrews, tenrecs and chrysochlorids, has been supported by numerous molecular and genomic studies. According to these molecular inferences, the origin of crown Afrotheria goes back into the Cretaceous, with estimates from over 100 to under 80 Mya. Morphological phylogenies have not completely recovered Afrotheria, although its paenungulate core (proboscideans, sirenians and hyracoids) was named in 1945 by the paleontologist George Simpson. Recent paleontological studies concur with molecular ones in evoking some affinities between paenungulates, aardvarks and elephant-shrews. Moreover, the position of tenrecs and golden moles within afrotherians is supported by some recent concatenations of morphological and molecular phylogenetic datasets. The phylogenetic position of Afrotheria relative to the other supraordinal placental clades has been debated, the most recent analyses of genomic and concatenated data support a basal position within Placentalia. Molecular data suggest an African origin for Afrotheria and a long period of endemism on that continent. When adding the paleontological data to this scenario, the paleobiogeographic history of Afrotheria becomes more complex. For instance, these data argue for the broad distribution of afrotherians during the Tertiary and do not exclude their Laurasian origin. In fact, some Laurasian taxa could be closely related to the earliest afrotherians (hyracoids, proboscideans and elephant-shrews) found in the early Eocene of North Africa. Other Afrotherian groups are known with certitude from East Africa since the beginning of the Miocene.