The ancestors of the lemmings (Lemmini, Arvicolinae, Cricetidae, Rodentia) in the early Pliocene of Wölfersheim near Frankfurt am Main; Germany

Abstract

More than 1000 isolated molars of the advanced cricetids with high-crowned molars (the subfamilies Arvicolinae; the “microtoid” Baranomyinae, Prometheomyinae and Trilophomyinae) from the early Pliocene (MN 15b) in the lignite quarry “Romerstrase” at Wolfersheim in the Horloff Basin about 30 km north-east of Frankfurt am Main represent the following forms:Mimomys (Mimomys) hassiacusHeller 1936,Mimomys (Cseria) gracilisKretzoi 1969,Dolomys occitanus (Thaler 1956),Germanomys weileriHeller 1936,Baranomys longidens (Kowalski 1960),Baranomys kowalskii (Kretzoi 1962) andTrilophomys vandeweerdiBrandy 1979. Later, more extensive examinations revealed the unexpected record of two new forms with rooted molars which represent ancestral forms of two lemming tribes of the subfamily Arvicolinae, the Synaptomyini (Tobienia kretzoii n. g., n. sp.) and Lemmini (Lemmini n. g., n. sp.). The new genusTobienia shows close affinities to the extant North American genus of the Northern Bog LemmingMictomysTrue 1894, the history of which in North America is described in detail. The oldest record,Mictomys vetus (Wilson 1934), has rootless molars and is about 1.5 Ma younger than the fauna of Wolfersheim. The assemblage of both mastodontsAnancus arvernensis andMammut borsoni and a tapirTapirus arvernensis, together with the advanced cricetids supports a Late Ruscinian (mammalian zone MN 15b, i.e. approx. 4 Ma) age for the Wolfersheim fauna.