Elliot’s red titi monkey, Callicebus usto-fuscus
In 1907 Elliot decribed a new species of titi monkey, Callicebus usto-fuscus (with hyphen), based in a specimen thought to originate from Brazil. He describes the species as being “allied to C. cupreus, but much darker in colour; practically the skull is larger in every way and more massive. General hue above burnt-umber, the hairs being slaty-grey at base, then annulated with two bands of slate- and two clay-colour, and a dark tip. top of head a mixed dark ochraceous rufous and black, the black predominating on the forehead; the rump is redder than the back and is a burnt-sienna on the outer side of the limbs; hands and feet claret-brown; sides of head, throat, inner side of limbs, and under parts maroon; basal third of tail black, the hairs being chestnut with broad black tips, rest of tail mixed black and yellowish grey or very pale clay-colour, the underside of tail being almost altogether clay-colour; ears black.
The species is generally thought to be a junior synonym of Callicebus cupreus (Hershkovitz, 1963; Groves, 2001) or Callicebus caligatus (Hershkovitz, 1990). As the species has reddish hands, I would regard it as a junior synonym of the first species.