Pleistocene evolutionary trends in dental morphology of Mimomys savini (Rodentia, Mammalia) from Iberian peninsula and discussion about the origin of the genus Arvicola

The study of Mimomys savini material from the Spanish sites of Barranco Leon and Fuente Nueva 3 (Granada), Gran Dolina (Atapuerca), Vallparadis (Barcelona) and La Boella (Tarragona) shows evolutionary trends in the dental morphology of this species within the Lower and early Middle Pleistocene. The data obtained from each site were ordered on the basis of absolute datings available for the ~1.46-0.7 Ma time interval. Clearly detected trends are the size increase and a successive reduction in enamel islets on both the upper third and lower first molar, and in the Mimomys ridge on the lower first molar. However, the SDQ (enamel differentiation index) values of the lower first molar show no clearly directed trend within the considered time range. On the basis of these evolutionary trends observed on Mimomys savini in the Iberian Peninsula, the phylogenetic relationship between Mimomys savini and the genus Arvicola is discussed.