Rapid colonization and diversification of a large-bodied mammalian herbivore clade in an insular context: New embrithopods from the Eocene of Balkanatolia

Abstract

Embrithopoda is an extinct clade of herbivorous placental mammals belonging to the afrotherian subclade Paenungulata. Early in their evolutionary history, embrithopods colonized the insular terrane of Balkanatolia, presumably via dispersal across the Tethyan marine barrier that separated Africa from Eurasia during the early Cenozoic. Here we report new embrithopods from the early Eocene locality of Çamili Mezra, Çiçekdaği Basin, central Anatolia, which document the early co-occurrence of two sympatric species of embrithopods, including Crivadiatherium sevketseni sp. nov. and Crivadiatherium sahini sp. nov. The genus Crivadiatherium, otherwise known only from the late Eocene of Romania, is reported for the first time in Anatolia. Hypsamasia seni from the middle Eocene of north-central Anatolia is interpreted as a nomen dubium. Embrithopod specimens previously described as Palaeoamasia sp. nov. from the Eocene-Oligocene transition of the Boyabat Basin in northern Anatolia are identified as a new genus and species, Axainamasia sandersi. The embrithopod fauna of Çamili Mezra indicates that this clade experienced at least a modest adaptive radiation after successfully colonizing Balkanatolia. The Balkanatolian record of embrithopod evolution contrasts with the evolutionary history of this clade in its native Africa, where sympatric embrithopod taxa have never been documented.