Wikipedia
Archetypomys
Archetypomys is an extinct genus of early Eocene rodent and the only member of the family Archetypomyidae. A single species, Archetypomys erlianensis, has been described from Inner Mongolia. Archetypomys was a very small rodent intermediate in morphology between the basal rodent family Alagomyidae and more advanced rodents (Meng et al., 2007).