Polystichum oblongipinnarum Li Bing Zhang, M.Q.Han & Yan Liu, 2018

Polystichum oblongipinnarum Li Bing Zhang, M.Q.Han & Yan Liu View in CoL , sp. nov. ( Figures 9 View FIGURE 9 , 10 View FIGURE 10 )

Type:— CHINA. Yunnan: Malipo County, Xiajinchang Xiang, Xinyan Village , inside a limestone cave, alt. 2050 m, 23°07 ′ 04 ″ N, 104°47 ′ 30 ″ E, 31 March 2017, Mengqi Han HMQ1362 (holotype IBK!) GoogleMaps

Diagnosis:— Polystichum oblongipinnarum is most similar to P. oblongum Ching ex W.M.Chu & Z.R.He in Kung et al. (2001: 228) in having habit small (lamina <12 cm), lamina thinly papery, and pinnae not aristate-spinulose on margin and rounded at apex, but the former has a ratio of lamina length to petiole length ca. 1:1, petiole scales not fimbriate on margin, and acroscopic pinna margins forming angles of ca. 90° with rachis, while the latter has a ratio of lamina length to petiole length up to 6:1, petiole scales fimbriate on margin, and acroscopic pinna margins often forming angles of ca. 120° or greater with rachis.

Plants perennial, evergreen, 7–12.5 cm tall. Rhizomes ascending, ca. 1 cm long, 0.6–0.8 cm diam., with remnant bases of old petioles; roots dull brown when dried, up to 7 cm long, ca. 0.3 mm diam. Leaves in tufts; petioles 6–8 cm long, 2.2–3 mm diam., basal portions covered with scales, scales ovate-lanceolate, 1.4–3× 0.4–0.7 mm, papery, dull brown, edges with short teeth, apex acuminate; distal petiole scales ovate-lanceolate, 0.9–1.3 × 0.25–0.5 mm, membranous, margins with irregular teeth, apex caudate. Laminae oblong-lanceolate, 1-pinnate, 4–7 × 2–2.2 cm, apex acute; rachises ca. 0.6 mm diam., scales ovate-lanceolate, light brown, 0.25–1.7 mm long including tip, 0.2–0.45 cm wide at base, margins sparsely ciliate, apex caudate. Pinnae 7–9 pairs, oblong, 0.7–1 × 0.6–0.8 cm, basalmost 0–2 pairs slightly reduced toward lamina base, basalmost pairs ca. 3/4 as large as middle ones, basalmost two pairs 0.5–0.7 cm apart, middle pairs 0.5–0.6 cm apart, all pinnae papery, alternate, hardly overlapping rachis, basiscopic margins straight, entire, acroscopic margins shallowly crenulate, basiscopic margins forming a (60–)80–90° angle with rachis, apex rounded, base cuneate and asymmetric, acroscopic sides much broader, pinna petiolues ca. 0.5 mm long, auricles rounded at apex, abaxially with microscales, microscales narrow-type, lanceolate, light brown, 0.36–0.72 mm long, ca. 0.05 mm wide at base, margins entire; adaxially glabrous; veins visible abaxially but somewhat obscure adaxially, lateral veins free, single or forked. Lowest 0–5 pairs of pinnae sterile; sori terminal on lateral veins of fertile pinnae, 1–5 on acroscopic side of fertile pinnae, 0–2 on distal basiscopic side of fertile pinnae, ca. 1 mm diam., closer to pinna margins than to costa (centers of sori 1–1.3 mm from pinna margins, 1.4–3.6 mm from costa), centers 1.4–2.5 mm apart from one another; indusia rounded, light brown, ca. 1 mm diam., margins nearly entire.

Geographical distribution:— Polystichum oblongipinnarum is only known from southeastern Yunnan, Southwest China, bordering northern Vietnam. It is likely endemic to the cave in Malipo County.

Ecology:— Polystichum oblongipinnarum grows inside a limestone cave at an elevation of 2050 m with humid and shady conditions.

IUCN Red List category:—CR-Critically Endangered: Only one population with about 50 plants was seen in the field.

Etymology:—The species epithet is based on the Latin prefix, oblongi-, oblong, and the Latin noun, pinna (genitive plural: pannarum), pinna, referring to the oblong pinnae of the new species.

Vernacular name:—AEOiNJHẄ(ju yuan yu er jue).

Notes:— Polystichum malipoense and P. oblongipinnarum were discovered in the same cave. Polystichum oblongipinnarum is most similar to P. oblongum and these two species both occur in high elevations, although the latter is found at a much higher elevation (ca. 3000 m) and is the species in P. sect. Haplopolystichum growing at the highest elevation known so far.