 A comparison of mitochondrial DNA found that "T. ucucha" was closest to specimens identified as "T. caudivarius" and "T. silvestris", but "T. hylophilus" was not included in this study.All are members of "Thomasomys", a diverse genus that occurs in the northern Andes, from Bolivia to Venezuela.Together with "Rhipidomys" and a few other, smaller genera, "Thomasomys" forms the tribe Thomasomyini, which includes over fifty species found in South America and Panama.