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ABSTRACT
A new species of Gliridae (Rodentia, Mammalia), Microdyromys remmerti, sp. nov., from the Aragonian type area in the Calatayud-Montalbán basin (Miocene, Spain) is described. This species is characterized by combining a relatively large size and a moderately complicated to very complicated and irregular dental morphology. It has a wide and continuous range of morphological variation with intermediate forms filling all the range. In the studied localities, M. remmerti, sp. nov., displays a general increase in the complexity of the dental pattern through time, showing a unique pattern of addition of extra ridges in the lower molars. Comparisons with morphologically similar species are discussed; a taxonomical and nomenclatorial issue regarding two named species of the genus is clarified. The combination of the morphometrical features that characterize M. remmerti, sp. nov., have never been found in any other glirid material outside the Calatayud-Montalbán basin, thus reinforcing the idea of the endemic character of the Gliridae faunas from the Iberian Miocene. Microdyromys koenigswaldi is proposed as most probable ancestor of M. remmerti, sp. nov. The divergent evolution of the latter species is discussed in its paleoecological context. The functional consequences of this morphological divergence could be related also with the opening of new ecological niches during the middle Aragonian (Middle Miocene).
ACKNOWLEDGMENTS
We thank all the colleagues and students who helped us in the field work for many years, L. W. van den Hoek Ostende and A. J. van der Meulen for their supportive comments and the translation of various texts from German, and S. K. Donovan for valuable suggestions on the English style of the manuscript and the nomenclatorial issues. We acknowledge the Nationaal Natuurhistorisch Museum Naturalis, Department of Earth Sciences of the Utrecht University (The Netherlands), and Museo Nacional de Ciencias Naturales, CSIC (Madrid, Spain), for the provided facilities to study their collections. Editor R. Asher, A. R. Evans, and an anonymous reviewer made constructive suggestions for improvement of the manuscript. We acknowledge financial support by the projects PB 98–0691-C03–02, CGL2004–02094/BTE, CGL2007–65208/BTE, CGL2008–04200/BTE, Research Group UCM 910607, and FECYT-MICIIN postdoctoral contract to I.G.-P.
