We analyzed two mitochondrial gene fragments to assess genetic divergence within the genus Desmomys endemic to Ethiopia and its phylogenetic relationships with related genera. The phylogenetic analysis supported the monophyly of the Arvicanthini-Otomyini group and revealed that Stochomys is clearly a member of Arvicanthini. Our study demonstrated that D. harringtoni and D. yaldeni belong to remarkably different mitochondrial lineages, the estimated divergence time between them is 4.10-5.38 Myr. Such early splitting of specialized forest dweller, D. yaldeni, from its sole congener supposes a more ancient formation of some elements of Ethiopian forest rodent fauna than is assumed today.