SUMMARY
Currently, four species of Nephelomys (N. childi, N. maculiventer, N. meridiensis and N. pectoralis) are known from Colombia. Here we present the first records of a fifth species, the rare Eastern Cloud Forest rat N. nimbosus, previously considered endemic to Ecuador and so far recorded only at five localities in the forests of the Eastern Cordillera. Four individuals of N. nimbosus were captured with Sherman traps at National Natural Park Cueva de los Guacharos in Huila Department, southern Colombia. Individuals were captured at two locations, a subandine primary forest at 2,000 m and at small cave ‘Cueva de los Guacharos’, at 1,900 m. Individuals were identified as N. nimbosus according to the following characteristics: ventral patche of self - colored white hairs in the gular region, ventral pelage ochraceous yellow with a golden tone, medium head-body size between 122 to 140 mm, incisive foramina between 4.6 and 5.1 mm with lateral margins rounded, posterolateral palatal pits small to big shallow and simple, hourglass shaped interorbital region, with supraorbital margins rounded or squared and a thin and delicate face. These new records increase the known species distribution by 760 kilometers to the north and present the first record of the species in Colombia. This first record of N. nimbosus for Colombia potentially extends the species distribution for northeastern Ecuadorian Cordillera and southern Colombian Cordillera. These results show the need to continue with the collection of specimens in poorly known species as N. nimbosus and in poorly known areas in Colombia, such as montane forests.