The Siberut macaque is a macaque endemic to Siberut Island in Indonesia. It was formerly considered conspecific with the overall paler Pagai Island macaque, but that arrangement was polyphyletic; both were formerly considered subspecies of the southern pig-tailed macaque (Wikipedia, general species account).
Description: Wildlife of Sumatra guide, Wildlife of Everywhere (wildlifeofeverywhere.com); general species information paraphrased from Wikipedia (CC BY-SA)
Mammals of the World