Evolución de los géneros Mimomys, Arvicola y Allophaiomys (Arvicolidae, Rodentia, Mammalia) en el Plioceno y Pleistoceno de la Península Ibérica

Abstract

A new interpretation of the philogeny of the arvicolids Mimomys, Arvicola and Allophaiomys is proposed in this paper as a result of the comparison between several faunas of the Pliocene and lower and middle Pleistocene of the Iberian Península. The morphologic study of the abundant populations of Mimomys of the Pliocene bed from Moreda, has made it possible to establish, for each species, four divisions according to the stages of wear of the first lower molar. The evolution of Mimomys is closely related to the qualitative and quantitative variations of those stages of wear (from the most primitive to the most progressive ones) in the course of the time and for each different populations of Mimomys, which leads us to propose the following scheme of the evolution of the genus: During the Pliocene, two evolutionary lines of Mimomys are present since the appearance of the genus in the Iberian Peninsula: one of small size, in which the acquisition of cement in the molars is progressive, That one is represented by the following evolutionary stages: M. stehlini in the Ruscinian and M. pliocaenicus-M, medasensis in the upper Pliocene. the other line, of big size, is represented by M. cappettai and the cement in the molars exists already in the niore primitive populations. At the end of the Pliocene appears M. reidi of small size, By its similar morphology, the latter species is very probably the ancestor of the bigger M. savini that belongs to the lower and middle Pleistocene. On the other hand, the morphologic identity and the biometric proximity of Allophaiomys chalinei to the populationsof small size of Arvicola (A. mosbachensis), leads us to propose the evolutionary line: Arvicola deucalion-Arvicola chalinei-Arvicola mosbachensis. Therefore, Mimomys is an independent and coetaneus genus of Arvicola that disappeared in the upper Pleistocene. Finally, Allophaiomys pliocaenicus gives rise to Microtus and Pitymys by a cladogenetic process of diversification.