Tree 10-15 m. Leaves chartaceous, elliptic-oblong or (oblong-)lanceolate, 19-38 by 5-12 cm, base rounded or attenuate, apex ± acute-acuminate; Inflorescences between the leaves and below, of the Knema-type: without peduncle, single or paired, woody, scar-covered tubercle-like brachyblasts to 5 mm long, ± with hairs 0.5 mm; Fruits solitary or 2 per infructescence, subsessile, broadly ovoid or ellipsoid, 2.5-3.5 by 2.5 cm, apex narrowly or broadly rounded, often 1-2 mm beaked, hairs dense, yellow-brown or rusty, shaggy, (1-)1.5 mm;
Asia-Tropical: Lesser Sunda Is. present, Sumbawa present, W Flores present
Malesia: Lesser Sunda Islands (Sumbawa, W Flores).
Myristica sumbawana is related to M. rumphii, with which it has much of the overall habit in common including the sessile flowers and ± small sessile fruits. Myristica rumphii differs from M. sumbawana in the shorter indumentum of the fruits (hairs 0.5 mm long only), glabrescent lower leaf surface, and the inconspicuous, slack hairs. The male flowers of M. rumphii are unknown, but possibly they are not very different from those of M. sumbawana. Both M. rumphii and M. sumbawana seem related to M. fatua, the latter differing in the persistent dense indumentum on the lower leaf surface, and the larger fruits and pedicellate flowers.