Natuna Langur

An inhabitant of Natuna Besar (Bunguran) Island in the South China Sea, well north of Borneo. Every source checked for this entry describes it as endemic solely to that island, with no confirmed population on the Bornean mainland — despite sometimes appearing on Bornean checklists, the evidence does not support treating it as a Bornean species, and any claimed Bornean sighting should be treated as exceptional and in need of independent verification rather than expected.

Originally described in 1894 and at various points classified as a subspecies of other langurs before being separated as a full species in 2001; genetic work estimates it diverged from relatives roughly a million years ago. Vulnerable (IUCN, assessed 2008), with fewer than 10,000 individuals estimated and heavy logging as the main threat.