Description from Flora of China
Rhizome erect, black, robust, woody, stiff, apex with dense scales; scales black, linear, 3-8 mm, thickly membranous, margin thin, dentate; fronds caespitose. Fertile frond ca. 1 m; stipe black at base, upward stramineous or pale brown-stramineous, 24-55 cm, ca. 4 mm in diam. at base, base with sparse narrowly lanceolate scales, upward glabrous; rachis stramineous, glabrous; lamina 1-imparipinnate, elliptic, 40-45 × 19-25 cm; pinnae 4 or 5 pairs, equal in size, oblique, stalked (stalk 4-8 mm), lanceolate, 20-25 × 4-4.5 cm, gradually narrowed, acuminate at apex, base cuneate, margin entire or dentate near apex, often incurved when dry; costae raised, rounded abaxially, shallowly grooved adaxially; veinlets prominent abaxially, visible adaxially, oblique or slightly oblique, 3 or 4 per veinlet group, straight, parallel, reaching margin of lamina. Lamina subleathery, dark green or brown-green when dry. Sori and indusia linear, 2 or 3 per veinlet group, brown, longest, double on acroscopic veinlet, basal sori long and close to costa, distal sori shorter.
Diplazium stenolepis is similar to D. hainanense but differs by the pinnae lanceolate, scales linear, and upper part of stipe and rachis glabrous.
Dense forests, beside streamlets; ca. 1000 m. S Guangxi, Hainan [N Vietnam].