Fat dormouse, a species from monotypic genus is the only member of Gliridae family that can be seen in Iran. Recently, a phylogenetic study based on mitochondrial Cytb confirmed Hyrcanian forests role as a refugium during Quaternary climatic oscillations. Further investigation, detailed sampling and combination of different data sets allowed us to identify two clearly and new divergent haplogroups of the Fat Dormouse along the Hyrcanian refugium of Northern Iran. Comparison of lower mandibles and skull characteristics of the specimens as well as sequencing one mitochondrial gene and three nuclear genes for new specimens revealed that the population restricted to the eastern most part of its global distribution in Iran, had been trapped in Kalaleh microrefugium and experienced distinct evolutionary history. The statistical analyses such as PCA, MANCOVA and DA applied to the morphological and ecological data confirmed the separation of the Kalaleh population as new subspecies.
