Description from Flora of China
Polystichum craspedocarpium Ching & W. M. Chu ex L. L. Xiang; P. deltodon (Baker) Diels var. marginale (Christ) C. Christensen; P. hecatopterum Diels var. marginale Christ.
Plants evergreen. Rhizome erect, short, 1-2 cm in diam. including stipe bases, upper part densely scaly; scales brown to dark brown or castaneous, lanceolate, up to 4 mm, thick, entire or with few short teeth. Fronds up to 50 cm, sometimes only 6 cm under dry conditions; stipe light stramineous, (0.5-)3-10(-18) cm, (0.6-)1-2 mm in diam., all covered with numerous scales similar to rhizome apex scales, but spreading and easily falling off. Lamina light green or light brownish green when dry, adaxially darker, narrowly elliptic-lanceolate, (4-)15-30 (-33) cm, middle (1-)2-3.5(-4) cm wide, with pinnae below middle slightly or obviously contracted, 1-pinnate, apex pinnatilobate to pinnatipartite, obtuse or shortly acuminate to long acuminate; rachis light stramineous, without proliferous bulbils, sparsely scaly; scales brown to dark brown or nearly castaneous, subulate-lanceolate, sparsely toothed; often covered with small appressed scales. Pinnae (8-)30-50(-60) pairs, sessile, usually approximate or imbricate, sometimes lowest pairs remote, alternate, rarely nearly opposite, attached at right angles to rachis or most pinnae ± angled basiscopically, few pairs ascendant, nearly oblong, lower pairs nearly right-triangular, middle pairs largest, 0.5-2 cm, 2.5-8 mm, apices obtuse-rounded or acute and slightly curved acroscopically, sometimes mucronate, bases asymmetrical, acroscopic base slightly auriculate, auricles deltoid with acute or shortly spinulose tip, proximal margins of auricles nearly truncate, parallel to rachis or slightly overlapping rachis, distal part of acroscopic margins nearly truncate, shallowly repand, sometimes apex with 1 or 2 teeth, sometimes with spinules, sometimes acroscopic base obtuse and without conspicuous auricles, basal basiscopic margins narrowly cuneate, truncate, margins entire, distal basiscopic margins curved, basiscopic margins repand or with 3 or 4 teeth similar to those on acroscopic margins; adaxially glabrous, abaxially sparsely covered with light brown or grayish white short and narrowly lanceolate microscales; frond texture papery; venation visible or distinct abaxially, indistinct adaxially, pinnate; lateral veins nearly reaching pinna margin, above midrib pinnate from base upward, dichotomous or simple, below midrib simple or dichotomous. Sori small, terminal on shorter veinlets, close to pinna margin, up to 9 above midrib, 1-3 or sterile below middle midrib, lower part of lamina often sterile; indusia present, grayish brown, entire, evanescent. Spores semicircular in equatorial view, perispore sculpturing sparsely plicate.
The name Polystichum pinfaense Christ is often treated as a synonym of P. dielsii. However, original material of P. pinfaense needs to be studied before any conclusions can be reached.
Polystichum dielsii is probably not distributed in Sichuan or NW Guizhou.
Broad-leaved evergreen forests, wet limestone and rock crevices around caves, rarely in dry limestone crevices at forest margins; 500-1600 m. W Guangxi, C and S Guizhou (Guiding, Wangmo), SE Yunnan (Xichou) [N Vietnam].