Tree 3-12 m. Leaves membranous, elliptic-oblong to oblong-lanceolate, 14-30 by 5-10.5 cm, base short-attenuate or rounded, apex acute-acuminate; Inflorescences: Fruits 1 or 2 per infructescence, ellipsoid, 2.4-4 by 1.7-2.5 cm, with persistent rust-brown hairs 0.1 mm long, dry pericarp 1-2 mm thick;
Asia-Tropical: Borneo present (Sarawak present), C Kalimantan present
Malesia: Borneo (Sarawak: possibly; C Kalimantan).
2 Veldkamp 8209 has considerably large female flowers, pedicel 12 mm long, buds 7 by 4 mm, ovary 4 by 3 mm, much larger than those in Veldkamp 7970 (a collection of mixed male and female specimens). 1 Knema riangensis is, among its relatives, characterized by a lower leaf surface with (sub)persistent dense slightly interwoven hairs of almost uniform size, 0.1-0.2 mm long, male buds small, 2 by 1.7 mm, cleft nearly to the base, androphore distinctly tapering, sometimes with a few minute hairs at base (which points to relationship with K. hirtella), anthers 9, sessile, suberect, close to each other, style distinct, 0.5 mm long (almost as in K. stylosa), and medium-sized fruits, with short persistent indumentum.