Type: — CHINA. Guangxi Zhuangzu Autonomous Region: Baise City, Napo County, Longhe Town, Yuantuo village, 23.3897°N, 105.9864°E, elev. ca. 1080 m, 18 October 2022, Chi Xiong & Zheng-long Li DXGJ20221018-06 (holotype IBK!)
Diagnosis: — Polystichum napoense is characterized by its rhomboidal or deltoidovate pinnae, deflexed basal pinnae, and a large number of scales present on both surfaces of the pinnae.
Description:—Plants perennial, evergreen, 12–26 cm tall. Rhizome erect, short, ca. 2.5 cm in diam., covered with scales; scales broad ovate-lanceolate, brown, c. 3–4× 1–1.5 mm, margin erose, apex caudate. Fronds cespitose, 6– 15 per rhizome, 12–28 cm long; stipes green, 1.5–3.5 cm long, 0.4–0.6 mm in diam., stramineous, adaxially shallowly canaliculate; densely scaly; scales on base of stipe long-triangular to lanceolate, membranous, dark brown, 1.5–3 × 0.5–1 mm, margin sparsely toothed, apex acuminate to caudate; scales on distal petiole similar but narrower. Lamina lanceolate, 9–25 × 2–2.5 cm, base slightly contracted, apex acuminate, 1-pinnate; rachis stramineous, covered with scales; scales lanceolate, narrowly lanceolate to sublinear, membranous, dark brown, 0.5–1.5 × 0.1–0.3 mm, with 1–3 teeth on margin, apex fibriform. Pinnae 10–25 pairs, chartaceous, greyish green, alternate, slightly imbricate, subexplanate, attached at 80–150° to rachis, short petiolate, rhomboidal or deltoidovate, 0.8–1.8 × 0.5–0.7 cm at middle, base asymmetric, acroscopic base auriculate, margin repand, basiscopic base truncate and forming a 15–40(–60)° angle with rachis, margin dentate, apex obtuse, both surfaces scaly; scales linear, filiform, ca. 0.5 mm long; veins pinnate, abaxially slightly distinct, adaxially indistinct. Sori terminal on veins of distal pinnae, close to pinna margin, 8–13 (3–5 below midrib, 5–8 above midrib) per fertile pinna; indusia absent. Sporangia almost round, 0.3–0.4 mm diam., ca. 0.1 mm thick, dark brown when mature; annuli with 15–17 thickened cells. Spores circular in the polar view and elliptic in the equatorial view, 43.8–47.5 (–50.3) × 50.8–59.4 (–63.8) µm (polar axis × equatorial axis); the ratio of the length of the polar axis to that of the equatorial axis is 0.74–0.87; perispore sculpturing is alveolate or forming large folds on it.
Distribution and ecology: — Polystichum napoense is currently found only from the type locality at an elevation of ca. 1080 m. This species grows on rocks in a karst cave, spanning from the entrance zone to the twilight zone.
Etymology: —Derived from the type locality, Napo County (Guangxi, China).
Vernacular name:—Ďāff̎ (nà pô ěr jué).
Conservation status: — Polystichum napoense is currently known only to exist in one population at the type locality. The population size is estimated to be around 100–150 mature individuals. Following the IUCN (The International Union for Conservation of Nature and Natural Resources) guidelines (IUCN, 2023), the species is temporarily assessed as Critically Endangered (CR).