The mantled titi monkey, Callicebus paenulatus

Elliot described in 1909 a new species of titi monkey, Callicebus paenulatus, based on a specimen originating from Andoas, on the Pastasa River in Ecuador. This species is characteried by a “very long fur, thick, and fluffy; mantle uniform colour, distinct from back; arms from elbows hands, feet, and legs above knees uniform colour”. The forehead is grizzled ochraceous. The validity of the species is disputed, and it is generally considered as a subspecies of Callicebus leucometopus.

We also question its validity, as Callicebus leucometopa (the species living in that region) is highly variable. The resemblance with the later described Callicebus caquetensis (lack of white frontal band, relatively long hairs of the back) warrants further research on the distribution range and validity of the latter species.