The big-eared climbing rat is in the order Rodentia and in the family Cricetidae and is most widely distributed species in the
genus Ototylomys. A second species of the genus was described in 2017 from the Mexican state of Chiapas. The genus dates back 3.35 Mya, prior to the Great American Biotic Interchange and Its initial occurrence was near Honduras and El Salvador.
Ototylomys is Greek for
otus (ear),
tylos (knob, knot, swelling), and
mus (mouse), which describes the animals large ears and shelf-like skull. The big-eared climbing rat is a slender rat with two colors; dark on top of its body and light below. Its eyes and ears are large. It has large naked ears and a long naked tail with scales. Its size and color varies depending on where it lives geographically but most populations have a creamy white underbelly except for those in Mexico and Guatemala, which have a slate-colored underbelly. The skull is flat on top and has a prominent interparietal bone and supraorbital ridges There is no sexual dimorphism in this species. ==Phylogeny==