The fossil record of fat dormice: A review of the past diversity and distribution of the genus Glis

The familiar fat dormice, Glis, are among the most characteristic European rodents. With only two living species, their modern diversity represents but relics of an impressive past radiation, dating back to the Oligocene epoch, some 30 Ma. Throughout most of their evolutionary history, members of the genus have evolved little from what is considered the primitive glirid morphotype. In this sense, fat dormice might be called living fossils. This paper discusses the past diversity of the genus Glis, reviewing our knowledge of all eleven currently recognized species and some problematic taxa. The Early Miocene G. complicatus is identified as a full species, distinct from morphologically more derived and geologically younger G. minor. The Middle Pleistocene G. percoi is synonymised with G. mihevci. Morphological trends within the genus include an increase in size, a tendency towards more heavily built, isolated, straightened and transversal lophs on more flattened occlusal surfaces, rudimentary accessory ridges, weaker anterotropes, and more parallel protoloph and metaloph of M1–2.