Castanopsis acuminatissima or commonly known as Papua New Guinea Oak is an evergreen tree that can grow up to 30 m tall and 50 cm in diameter. It has flaky or sometimes smooth bark that yellowish-grey in colour while the inner bark is brownish-yellow. This species has yellowish sapwood. The twigs are densely pubescent (hairy) when young and will become glabrous (smooth) later. The stipules are triangular. The leaves are coriaceous (having the texture of leather) with petioles of about 5 to 7 mm long. Its male flowers are solitary but densely arranged along the rachis with obtuse perianth lobes while its female flowers are solitary along the rachis with acute perianth lobes. The cupules are (sub)sessile, asymmetrical and has one seed in each cupule (Soepadmo & Saw, 2000).

Castanopsis acuminatissima is widely distributed in Malaysia, India, China, Taiwan, Thailand, Myanmar and Indo-China. In Sabah, it was recorded from Kota Marudu, Keningau and Ranau districts while in Sarawak, it is uncommon and only known from Sg. Menalio in Marudi district. It inhabits in the primary lowland mixed dipterocarp forest to montane forest at 300-2500 m altitudes. This species has a few uses where the bark is a source of tannins which play a role in protection from predation and industrial applications. The seeds are also edible which it can be used as a food source for people (Soepadmo & Saw, 2000).