As of January 2020, the International Union for Conservation of Nature (IUCN) listed 203 critically endangered mammalian species, including 31 which are tagged as possibly extinct. Of all evaluated mammalian species, 3.5% are listed as critically endangered. The IUCN also lists 60 mammalian subspecies as critically endangered.
Of the subpopulations of mammals evaluated by the IUCN, 18 species subpopulations have been assessed as critically endangered.
The Tapanuli orangutan (Pongo tapanuliensis) is a species of orangutan restricted to South Tapanuli in the island of Sumatra in Indonesia. It is one of three known living species of orangutan, alongside the Sumatran orangutan (P. abelii), found farther northwest on the island, and the Bornean orangutan (P. pygmaeus). It was described as a distinct species in 2017. As of 2018, there are roughly 800 individuals of this species and it is currently on the critically endangered species list.