Tree 8-30 m. Leaves membranous to chartaceous, elliptic to oblong-lanceolate, 13-35 by 5-13.5 cm, base (short-) attenuate, apex acute-acuminate; Inflorescences with woolly hairs 0.5-1 mm long; Fruits 2-8 per infructescence, broadly ellipsoid to subglobose (seeds ellipsoid), 2-2.4 by 1.6-2 cm, largely glabrescent but with minute vestigial hairs towards the base, tubercles coarse, pale, lenticel-like, pericarp woody-coriaceous, 4-7 mm thick;
Asia-Tropical, Bird's Head present, Papua Barat present, Papua New Guinea present, West Sepik Prov present
Malesia: Papua Barat (Bird's Head); Papua New Guinea (West Sepik Prov. ).
The male buds are deeply cleft, to 3/4-5/6, much deeper than in the other members of the group of species with H. hellwigii, to which H. leptantha belongs. The fruits with coarse lenticels and tubercles are reminiscent of those in H. laevigata, and possibly there is a close relationship with this species.