Mimomys savini size evolution in the Early Pleistocene of south-western Europe and possible biochronological implications

Abstract

Over the course of their evolutionary history, some species of mammals have undergone variations in size, with a general trend towards increased morphometry. This effect can be seen very clearly in the fossil record of rodents because their high rate of reproduction that generates a high fossil record, which allows this phenomenon to be studied in detail. Furthermore, the rapid geographic distribution of rodents means that their evolution can be studied on a continental scale.If a relationship can be established between the size of individuals and their chronology, and the trend that governs a species' increase in size can be determined, then the chronologies of different sites can be estimated based on the size of the individuals of that species recovered at those particular sites. The correlation between morphometric data of micromammal fossils and age was already used by other authors.This article studies the rate at which the length of the first lower molar (m1) of Mimomys savini (a species of Palearctic arvicoline present in Europe between approximately 1.8 and 0.6 Ma ago) increased over the course of its evolution in Iberian Peninsula (south-western Europe). Because this increase in length occurred at a constant rate, a direct relationship can be established between average length of m1 and chronology, which allows us to set numerical dates to Pleistocene sites containing Mimomys savini remains.