The Caquetá titi monkey, Callicebus caquetensis
An isolated species of white-browed titi monkeys in southern Colombia was reported in 1976 by Moynihan, and described in 2010 by Thomas Defler and his colleagues as Callicebus caquetensis.
This species, distributed south to the Caquetá River, is reported to be very similar in color and markings to C. ornatus and C. discolor, though it lacks the white forehead bar of both of those species and the white hands and feet of C. ornatus. The crown is a light buffy brown; the neck, sides, back and tail are mixed grayish-brown and buffy agouti but often with penciled tail tip on terminal third of tail that is dominantly white and black agouti. The coloration is sparsely-haired chestnut-red on the ventrum, body, arms, legs and face, extending to dorsal parts of lower arms and lower legs up to the elbows and knees. The reddish also extends to the ventral parts of the neck and onto the cheeks up to the basal parts of the ear, giving the appearance of a red beard. The grayish-brown agouti extends from the back onto the dorsal parts of the arms and legs down to the knees and the elbow, also with some slight reddish washing.
I should note that a very similar species, Callicebus paenulatus, was described in 1909 by Elliot. However, the holotype was thought to originate from Andoas, on the Pastasa River in Ecuador. This is much further south as the Caquetá River, and possible just a local variation of Callicebus leucometopus.