West European arvicolid evidence of intercontinental connections during the Early Pleistocene

摘要

Early Pleistocene arvicolid faunas from the Norwich Crag Formation of the UK contain species found across Eurasia, indicating that this was then a single faunal province. Several examples of arvicolid evidence for intercontinental connections are discussed, with reference particularly to new material from the locality Easton Wood, Suffolk, UK. This includes teeth referred to Mimomys glendae sp.nov., apparently closely related to Siberian and North American species. The locality also provides the earliest UK occurrences of Lemmus kowalskii and Mimomys tigliensis, a wide ranging and biostratigraphically important species. The immigration of M. tigliensis to West Europe took place in arvicolid zone MNR2 at a time apparently close to its appearance in Russian faunas. The faunas from Easton Wood and the Netherlands support the current arvicolid Early Pleistocene biozonation of South East Europe suggesting that it is applicable to at least the northern part of West Europe. The age of the Norwich Crag deposits at Easton Wood is estimated according to this scheme at between 2.25 and 2.35 Ma, indicating that palaeomagnetic inferences previously used to support a younger age require review.