New ideas on the systematics of Gliridae (Rodentia, Mammalia)

Resumen

Extant members of the family Gliridae lack a caecum and are not capable of digesting hard (cellulose) plant material. We assume that they did have a caecum at some time in the past and consequently may have had a different diet. We think that during the period of their maximum diversity in the Early Miocene, about 16 My ago, they still possessed the caecum, which allowed for a much greater variety in diet, as may be reflected by the existence of hypsodont taxons, and that they lost it afterwards. It is, however, unlikely that the three recent subfamilies that existed in the Miocene, Glirinae, Myomiminae and Dryomyinae, lost the caecum independently; the alternative is that all modern glirids are derived from one single Middle Miocene species. If that is true the few occurrences of the recent genera in MN4 or older, should be transferred to other, eventually new, genera. This is consistent with the fact that the distributions of the extant genera before MN9 are discontinuous and that, except for Muscardinus, they are absent in MN6-MN8 (14-11 My ago)