sumatran orangutan

* Genus Pongo [1]
o Bornean Orangutan (Pongo pygmaeus)
+ Pongo pygmaeus pygmaeus - northwest populations
+ Pongo pygmaeus morio - east populations
+ Pongo pygmaeus wurmbii - southwest populations
o Sumatran Orangutan (Pongo abelii)

Pongo pygmaeus

The populations on the two islands were classified as subspecies until recently, when they were elevated to full specific level, and the three distinct populations on Borneo were elevated to subspecies. The population currently listed as P. p. wurmbii may be closer to the Sumatran Orangutan than the Bornean Orangutan. If confirmed, abelii would be a subspecies of P. wurmbii (Tiedeman, 1808).[30] Regardless, the type locality of pygmaeus has not been established beyond doubts, and may be from the population currently listed as wurmbii (in which case wurmbii would be a junior synonym of pygmaeus, while one of the names currently considered a junior synonym of pygmaeus would take precedence for the northwest Bornean taxon).[30] To further confuse, the name morio, as well as various junior synonyms that have been suggested,[1] have been considered likely to all be junior synonyms of the population listed as pygmaeus in the above, thus leaving the east Bornean populations unnamed.[30]

In addition, a fossil species, P. hooijeri, is known from Vietnam, and multiple fossil subspecies have been described from several parts of southeastern Asia. It is unclear if these belong to P. pygmaeus or P. abeli or, in fact, represent distinct species.