Fat dormouse (Glis glis), belonging to the monotypic genus Glis of the family Gliridae, has been frequently used as a model to enrich our knowledge of patterns of arboreal species adaptation to the glacial oscillations. Ancient Hyrcanian forests, as one of the old-growth relicts of the temperate deciduous forests, have been recently documented as an important refugium during the last glacial maximum (LGM). More investigations based on skull and mandible morphological assessments revealed considerable intraspecific evolutionary divergence among the local populations settled in the Hyrcanian forests of northern Iran. Geometric morphometric approaches in this study confirm the presence of multiple cryptic refugia for Fat dormouse as a small forest-dwelling species during paleontological oscillations. Such findings correspond to those of previous molecular and niche analyses. Our research also confirms an ideal capability of morphological approaches in species evolutionary assessments
