Tree 10-12 m. Leaves membranous or (thinly) char-taceous, oblong-lanceolate, 14-20 by 3.5-5 cm, base short-attenuate or narrowly rounded, apex acute-acuminate; Inflorescences (from incomplete female and fruiting specimens): of the Knema-type: a sessile or 2(-3) mm pedunculate, scar-covered brachyblast 2 mm long, with 2 or 3 flowers (according to their scars), minutely pubescent; Fruits (somewhat immature) solitary, broadly fusiform, 4.5 by 2.5 cm, apex acute with 3 mm long beak formed by style-remnant, base ± narrowed into a 3 mm long pseudostalk, hairs dense, rust-coloured, scurfy, 0.1 mm;
Asia-Tropical, Papua New Guinea present, W Sepik Prov., Telefomin subprov., near Busilmin present
Malesia: Papua New Guinea (W Sepik Prov., Telefomin subprov., near Busilmin); known only from the type area.
This species keys out beside M. pachyphylla to which it is similar and closely related. The two specimens now known of M. leptophylla differ in larger and thinner leaf blades, and in slightly larger fruits with stouter fruiting pedicel, sessile or on a short peduncle. Myristica tamrauensis, from Bird's Head, is similar too.