Nasa Weigend ser. Carunculatae (Urb. & Gilg) Weigend is revised, four species are recognized, and one, Nasa usquiliensis Weigend, T. Henning & C. Schneider described as new to science. The species of this group are restricted to steep scree slopes in Peru and southern Ecuador and have patchy distributions at elevations of 2200–3500 m. All species share shrubby habit with ligneous stems and deciduous foliage. These characters in combination with clawed, spreading petals and bicolored nectar scales are unique in Nasa. Branched root-tubers are reported from N. carunculata, which is the first report of tuberous storage roots in the genus. Species delimitation is primarily based on habit, trichome characters, flower size, petal color and shape, and the morphology of the floral scales.