First evidence of Microdyromys (Gliridae, Rodentia, Mammalia) in the Early Pliocene of the Balearic Islands and its bearing on the origin of the late Neogene insular dormice from the western Mediterranean

Abstract This paper reports the first occurrence of the dryomine dormouse Microdyromys in the Balearic Islands. Microdyromys boveri sp. nov. is characterized by lower molars with anterolophid, anterotropid, metalophid, centrolophid, mesolophid, posterotropid and posterolophid, and by upper molars with anteroloph, protoloph, metaloph and posteroloph as well as well-developed prototrope, precentroloph, centrotrope, postcentroloph, metatrope and posterotrope. In many cases this dental pattern is replaced by one formed of several small ridges and cuspules, in which the ridges cannot be identified. This dental pattern clearly differs from the much simpler one of Eliomys , which has been regarded as the direct ancestor of the endemic Balearic genus Hypnomys . The presence of Microdyromys boveri challenges this phylogenetic hypothesis, Hypnomys rooting in a late Miocene species of Microdyromys . This could have been also the case for other Plio-Pleistocene endemic genera from the western Mediterranean, such as Thyrrenoglis (Sardinia) and Maltamys (Malta, Sicily). The closest affinities of Microdyromys boveri are with the species Microdyromys chaabi from Oued-Zra (Morocco), suggesting a North African origin. Its presence in Mallorca could therefore be linked to the regression caused by the Messinian salinity crisis.