Thomas’ Atlantic titi monkey, Callicebus personatus brunello
In 1913 Oldfield Thomas described a new subspecies of tit monkey, from North Eastern Sao Paulo, that differed from the already known subspecies. He named it Callicebus personatus brunello, and described it as having “general characters as in true personatus, including the extent of black on the face, crown, ears, hands, and feet, and in this respect similarly differing from C. nigrifrons, in which only a narrow frontal band is black, the crown being dark grey. Whole of upper surface greyish brown, this colour extending uniformly over the nape, shoulders, and back. Under surface similarly brown, without any tinge of reddish on the chest. Fore limbs proximally a similar greyish brown, inconspicuously speckled with buffy, very different from the conspicuously whitish forearms of true personatus; hands and wrists black”. “In the Espiritu Santo specimens (= true personatus) the upper surface and especially the nape, shoulders, and arms down to the wrists are broadly washed with pale greyish white”.
Later authors consider this form to be a synonym of Callicebus nigrifrons.