A new species of disk-winged bat (Thyroptera) is described from the savannah habitats of the Cerrado in Brazil and Rupununi in Guyana. It is most similar to the primarily forest-dwelling T. lavali because of shared morphology, including oval-shaped disks on the thumbs as opposed to circular disks in the other species (T. tricolor and T. discifera). However, the new species has distinct countershading with dark brown dorsal fur that is in contrast to pale brown ventral fur with frosted tips. The other species have either white or yellowish brown ventral fur. During the examination of comparative material for this description, some older material that was faded in color and previously reported as T. tricolor was assigned to T. discifera, representing a range extension of more than 1,000 km to the east and the 1st documentation of T. discifera in the Atlantic Forest of Brazil.