Article: A new species of Karydomys (Rodentia, Mammalia) and a systematic re-evaluation of this rare Eurasian Miocene hamster
Thomas Mörs and Daniela C. Kalthoff
We describe a new species of the rare and enigmatic cricetid genus Karydomys from the middle Miocene Ville Formation of the Hambach lignite mine in north-west Germany. The locality Hambach 6C has yielded the first substantial records of Karydomys from central Europe. For the first time, all molar positions are well-documented, including the previously unknown m2. The excellent molar material allows us to distinguish Karydomys wigharti sp. nov. from the western European species K. zapfei. Karydomys wigharti predominantly occurs at localities that are correlated with the upper part of the Mammalian Neogene biozone MN 5. The new finds are of palaeobiogeographic significance for the genus Karydomys, since Hambach 6C represents the north-westernmost outpost of terrestrial Miocene faunas in Europe. In addition, the locality has yielded the first lower jaws and incisors of the genus. Both the jaw morphology, and the ornamentation and microstructure of the incisor enamel offer new arguments for a systematic classification of Karydomys into the subfamily Democricetodontinae. We assume that the scarcity of the two large European Karydomys species can be explained by their special adaptation to wet habitats, which are poorly documented in the fossil record.