Description from Flora of China
Plants evergreen. Rhizome erect or ascending, short, densely covered with lanceolate grayish brown scales. Fronds 30-60 cm; stipe dark brown, 8-20 cm, 2.5-4 mm in diam. at base, densely covered with linear, lanceolate and larger scales; large scales ovate and ovate-lanceolate, up to 14 × 7 mm, densely serrulate, caudate or acuminate. Lamina bipinnate, deltoid-ovate, deltoid-lanceolate, or lanceolate, 20-45(-60) × 6-17 cm near base, base not contracted, lower part sterile, apex acuminate, fertile; rachis without proliferous bulbils, abaxially densely covered with linear, lanceolate, grayish brown scales and larger scales; large scales ovate-lanceolate and narrowly lanceolate, up to 8 × 3 mm, with dense small teeth, caudate. Pinnae 14-29 pairs, alternate, slightly ascendant, shortly stalked, lanceolate, gradually contracted toward base, bases asymmetrical, apices acuminate; lower pinnae 3.7-11 × 1-1.5 cm, 1-pinnate; costa adaxially sulcate, abaxially densely covered with linear grayish brown scales. Pinnules 13-23 pairs, alternate, shortly stalked, oblong, 0.8-1.2 cm × 3-4.5 mm, bases cuneate, acroscopic margins entire or slightly repand, with acute auricles, margins with only few (2 or 3) spinules, apices acute with acute tips; basal acroscopic pinnules largest, entire or incised; abaxially densely covered with long-filiform microscales, adaxially subglabrous; frond texture papery; venation pinnate, lateral veins 4-6 pairs, dichotomous, relatively distinct. Sori 3-6 per pinnule, in 1 row on each side of midrib, or only 1 row acroscopically, close to midrib, terminal on veinlets; indusia present, subentire.
Laminae of Polystichum parvipinnulum are often small, deltoid or deltoid-lanceolate, and nearly papery. Its pinnules are small and with very few spinules on the margins.
A hybrid, Polystichum ×pseudoparvipinnulum Miyamoto & T. Nakamura (J. Jap. Bot. 58: 146. 1983), possibly between P. parvipinnulum and P. piceopaleaceum, was described from Taizhong, Taiwan.
● Forests; 700-2400 m. Taiwan.