Comparison of Miocene Xerini (Sciuridae, Mammalia) from Central Spain and Germany

Abstract

Despite the extensive record of sciurids of the tribe Xerini from Miocene European localities, few have been the works that have tried to present an overview of his group at continental scale (Cuenca Bescos, 1988; De Bruijn, 1999; Aguilar, 2002). The xerini squirrels have a characteristic dental morphology that can be easily recognized by mammal paleontologist. The few species described within this tribe show a very similar dental morphology and the diagnostic characters for the diverese genus are in most cases mino differences, due to the maintenance of primitive dental patterns. This characteristic, and rather conservative, morphology has promoted in our opinion, an oversimplified taxonomy. This is specially evident on the genus Hetereoxerus Stehlin & Schaub, 1951, with a temporal distribution of around 20 My, and only six species described (De Bruijn, 1999). This work shows a morphological comparison between the xerine record of central Spain and Germany. Most of the materials recorded from these areas have been assigned to Heteroxerus rubricati, H. Huerzeleri and H. grivensis (Cuenca Bescos, 1988; Ziegler & Fahlbush, 1986; Ziegler, 2005). The comparison has demonstrated the existence of constant morphological differences between the ground squirrels from these two areas. This result shows the existence of taxonomical differences, not indicated by previous authors, and points out the need for a revision of this tribe in order to have a better understanding of its evolution and paleobiogeography. This result also reinforces the idea of a strong bioprovincialism during most part of the Miocene postulated on the basis of other mammal groups.