The oldest Cenozoic mammal fauna of Europe: implication of the Hainin reference fauna for mammalian evolution and dispersals during the Paleocene

Abstract

The mammal fauna of Hainin is particularly interesting as the oldest in the Cenozoic of Europe, and the earliest reference level (MP1–5) of the mammalian biochronological scale for the European Palaeogene. This paper summarizes the mammal taxa discovered in the fauna, presents an analysis of the fauna as a whole (relative abundance and species richness), and describes four new eutherians: Belgoryctes thaleri gen. et sp. nov., Eurolestes dupuisi gen. et sp. nov., Quadratodon sigei gen. et sp. nov. and Cingulodon magioncaldai gen. et sp. nov. The assemblage is relatively small (about 400 dental specimens), characterized by a high diversity and abundance of small insectivorous species and very low abundance of ‘plesiadapiforms’ and ‘condylarths’. By comparison with younger European Paleocene faunas, ‘condylarths’ and ‘plesiadapiforms’ became more and more abundant and diverse through the Paleocene but collapsed at the Paleocene–Eocene Boundary. ‘Proteutherians’ declined steadily, while multituberculates remained diverse, although the early Paleocene was populated mainly by Kogaionidae whereas the late Paleocene was dominated by Neoplagiaulacidae. The palaeoecology of Hainin is deduced from the mammal assemblage: the local environment was likely a forested area. Stratigraphically, the Hainin deposits are most likely of late Danian age, and biochronologically its fauna represents a partial equivalent of the North American Torrejonian Land Mammal Age. When compared to younger Paleocene faunas of Europe, the composition of the Hainin fauna reveals that a relatively important intercontinental dispersal of mammals occurred around the Danian–Selandian boundary, roughly corresponding to the Torrejonian–Tiffanian boundary. This dispersal is marked by the arrival in Europe of typically North American taxa such as arctocyonids, plesiadapids and neoplagiaulacid multituberculates. Additional exchanges of lesser magnitude probably also occurred around the Selandian–Thanetian boundary (i.e. during the Tiffanian), although the evidence is less compelling and mainly concerns the plesiadapids Chiromyoides and Plesiadapis.http://zoobank.org/urn:lsid:zoobank.org:pub:A240BAE2-7446-4DBD-A597-7BEFE58447DF