Systematics of the insular giant fossil dormice (Rodentia: Gliridae) of the Mediterranean

The dormice (Gliridae) are a family of rodents currently represented by 29 extant species, but with a greater fossil diversity stretching back to the early Eocene. The extant forms are generally small, but some fossil species on islands evolved larger body size through the phenomenon of insular gigantism. The phylogeny of dormice has historically been unstable, with between three and five subfamilies recognized and considerable movement of species between them. Recent molecular work has led to greater consensus on the systematics of the extant forms, but there remains some uncertainty about the placement of some giant fossil species, especially the Siculo-Maltese genus Leithia. Here we review our understanding of the phylogeny of dormice, explore some of the important outstanding questions regarding the systematics of the giant fossil forms, and propose future directions for research on this family of rodents.