Japanese dwarf flying squirrels have evolved differently from other sciuridae. The differences between Japanese dwarf flying squirrels and other sciuridae is evident when comparing morphology of the mandible and genetic code. The mandible of the Japanese dwarf flying squirrel does not have a coronoid process unlike the dwarf tree squirrel. The marmota also has a more elongated mandible than the Japanese dwarf flying squirrel. This is due to phylogeny and ecology.[7] There are also large differences in chromosome structure between P. momonga and the only other member of the Pteromys genus, Pteromys volans. Though they have the same number of chromosomes (2n=38), their karyotypes differ extensively due to pericentric inversions, tandem fusions, and deletion of large segments of the autosomes and the Y chromosome. Because of these deletions, the P. volans genome contains about fifteen percent less DNA than P. momonga. These findings suggest that the karyotype of P. momonga more closely resembles the ancestor of P. volans and P. momonga.[