Stratigraphic and taxonomic revision of the fossil vole remains (Rodentia, Microtinae) from the Lower Pleistocene deposits of eastern England

Abstract

We review the fossil microtine rodent assemblages from the Lower Pleistocene deposits in eastern England, consisting mainly of marine sediments of the Norwich Crag and Cromer Forest-bed Formations. Material from 17 localities, including the ‘Weybourne Crag’ of the Norfolk Coast, the inland ‘Norwich Crag’, and the Crag of the north Suffolk coast has been studied. The taxa Mimomys pliocaenicus, M.rex, M.blanci, M.newtoni, M.pitymyoides, M .altenburgensis and Clethrionomys are recognized. Mimomys pitymyoides and M.altenburgensis are described for the first time from Britain. The type material of Mimomys reidi and M.newtoni is redescribed, and we show that M.newtoni Major 1902 is a senior synonym of M.hungaricus (Kormos), thus resolving confusion that has existed in the literature. The prior name for the species described by M. A. C. Hinton ( Monograph of the voles and lemmings (Microtnae) living and extinct . London: British Museum (Natural History) 1926) as Mimomys newtoni appears to be Mimomys blanci van der Meulen 1973. No evidence has been found for mixing of faunas of different age at a single horizon or locality. Differences in crown height are demonstrated between samples of Mimomys pliocaenicus from different localities, and differences between localities in the presence and absence of various species are tabulated. This evidence combined with current interpretations of the stratigraphy leads us to recognize three faunal groups. Group 1 faunas contain Mimomys pliocaenicus, M.reidi (type level), M.newtoni (type level), M.pitymyoides, M.blanci and Clethrionomys . They come from coastal deposits previously termed ‘Weybourne Crag’ and currently considered to date from Pre-Pastonian a to Pastonian. The faunas are clearly later than group 2 faunas, which contain Mimomys pliocaenicus, M.reidi, M.newtoni (these three species less advanced than in group 1 faunas), M.rex and M.altenburgensis (these two species lacking in group 1 faunas). Group 2 faunas come from inland ‘Norwich Crag’ localities and crags in Suffolk yielding a Chillesford type pollen assemblage, which are currently considered to date from the Bramertonian stage. Group 3 faunas contain Mimomys pliocaenicus, M.reidi and M.blanci and are from coastal deposits at Covehithe and Easton Bavents associated with Baventian stage clays. The evidence from the microtine rodents confirms the relative position of the Bramertonian and Pre-Pastonian a stages, but does not yet allow conclusions to be drawn on the relative age of group 3 faunas or the deposits in which they occur. The fauna of the Pastonian stage still requires clarification, since it is not possible to allocate unambiguously to this stage any of the material described here. The British Lower Pleistocene assemblages are broadly similar to material from Tegelen, The Netherlands (Tiglian TC4-6) and to material from superimposed loess levels at Stranzendorf, Austria. The British assemblages are characterized by the presence of Mimomys pliocaenicus and the absence of species with unrooted teeth, indicating that they belong to the Mimomys superzone of the biostratigraphic system of A. J. van der Meulen ( Quaternaria 17, 1-144, 1973) corresponding to the Villanyian stage. On the basis of microtine evidence we suggest limits to the correlation of the Pre-Pastonian and Bramertonian stages with the Netherlands chronostratigraphy. These limits are earlier than suggested by other lines of evidence. Correlation of the Pre-Pastonian with part of the Eburonian and the Bramertonian with part of the Tiglian is thought to merit consideration.

Biostratigraphic and aminostratigraphic constraints on the age of the Middle Pleistocene glacial succession in north Norfolk, UK

“…In an earlier account (Stuart, 1996) the water vole molars then available included some that were clearly rooted and therefore attributable to Mimomys. Re-examination of the original specimens and rare Mimomys molars in the new samples has confirmed the initial diagnoses as Mimomys, including Mimomys pliocaenicus, the dominant vole in the 'Weybourne Crag' (Mayhew and Stuart, 1986), but their preservation is quite unlike that of other fossil vertebrates from the Sidestrand Hall Member. It is now clear that they are reworked from the 'Weybourne Crag'.…”

Biostratigraphy and correlation of the Monte Hermoso Formation (early Pliocene, Argentina): The evidence from caviomorph rodents

“…For example, the biostratigraphy of the European Neogene continental deposits is based mostly in rodents (e.g. Mayhew and Stuart, 1986;Agustí, 1990;Cuenca-Bescós et al, 1992, 2010Fejfar et al, 1997Fejfar et al, , 1999Hernández Fernández et al, 2004;Minwer-Barakat et al, 2011).…”

Small mammal assemblages from the Quaternary succession at Moriaanshoofd (Zeeland, the Netherlands) and their significance for correlating the Oosterschelde fauna

“…obs.) at a depth of c. 92-93 m. An M3 lacking an islet, from the Norwich Crag of Covehithe, Suffolk, UK, similar in general size and morphology to NMR7378 but with higher enamel-free areas, was shown in Mayhew and Stuart (1986) as Mimomys sp. It remains to be seen if this represents individual variability or a phylogenetic relationship.…”