Description from Flora of China
Polystichum deltodon (Baker) Diels var. acutidens (Christ) C. Christensen; P. subauriculatum Tagawa.
Plants evergreen. Rhizome erect, up to 10 cm, together with remnant old stipe base up to 3 cm in diam., rhizome apex and stipe base densely scaly; scales brown or dark brown, ovate or ovate-lanceolate, up to 8 × 3 mm, thickly membranous, entire. Fronds 25-100 cm; stipe stramineous, 5-40 cm, 1-2 mm in diam. at base, sparsely scaly upward, a few distal stipe scales similar to basal stipe scales; more distal stipe scales gradually narrower toward rachis apex, brown or dark brown, lanceolate or narrowly subulate, mostly appressed, membranous, with sparse long teeth. Lamina 1-pinnate, green or grayish green when dry, adaxially darker, lanceolate, 18-65 × 2.5-12 cm, slightly contracted or not at base, acuminate; rachis stramineous, without proliferous bulbils, sparsely scaly abaxially; scales often appressed, brown or dark brown, lanceolate, linear, or narrowly subulate, sparsely toothed, membranous. Pinnae 25-45 pairs, sessile, alternate or opposite, lower pairs more remote and sometimes angled acroscopically, upper pairs contiguous, falcate-lanceolate, 1-6 cm × 3-10 mm at middle, apices acuminate, often spinulose, bases obviously asymmetrical, acroscopic base with deltoid auricles, proximal margins of auricles truncate or slightly curved outward, parallel to rachis, basal basiscopic margins narrowly cuneate, straight or slightly recurved, both acroscopic and basiscopic margins toothed, tips of teeth often ± recurved and shortly or long spinulose; adaxially glabrous, abaxially sparsely covered with narrowly lanceolate light brown or brown microscales; frond texture papery or thinly papery; venation pinnate, visible or distinct abaxially, indistinct adaxially; lateral veins pinnate above midrib from base to apex, dichotomous or simple, simple or dichotomous below midrib. Sori small, terminal on shorter veinlets, in 1 row on each side of midrib, medial or nearly medial, veinlets of lower part below midrib often without sori; indusia present, dark brown, small, subentire, caducous. Spores reniform in equatorial view, narrowly elliptic in polar view; perispore sculpturing plicate with numerous granules.
Polystichum acutidens was placed in P. sect. Polystichum by Fraser-Jenkins (Himalayan Ferns (Guide to Polystichum), 7. 1997).
Montane broad-leaved evergreen forests, often in wet limestone valleys; 600-2400 m. Guangxi, Guizhou, Hubei, Hunan, Sichuan, Taiwan, SE Xizang, Yunnan, Zhejiang [N India, Myanmar].