The skull and mandible, with complete dentitions, of an Orellan rodent are described as a new genus and species of Eumyinae (Rodentia, Muroidea, Cricetidae) based on a combination of unique and shared features: small molar series compared to skull size, featherlike diagonal ridges on surface of lower incisor enamel, rounded triangular shape of M3, and flat interorbital roof and separate temporal crests.