Polystichum hastipinnum G.D. Tang & Li Bing Zhang, 2017

Polystichum hastipinnum G.D. Tang & Li Bing Zhang View in CoL , sp. nov. ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 & 3 View FIGURE 3 ).

Type:— CHINA. Guangdong Province: Shaoguan City, Luokeng Nature Reserve , 24°31’35’’N, 113°21’06”E, in a limestone cave, elev. ca. 220 m, 15 Feb. 2017, Guang-Da Tang, Lin Huang, Jia-Yu Li & Chu-Meng Zhu LK170215 (holotype CANT! GoogleMaps ; isotype, MO! GoogleMaps ).

Diagnosis:— Polystichum hastipinnum is similar to P. kwangtungense Ching (1958 : pl. 236) in having oblong pinnae and adjacent geographical distributions, but the former has stipe and rachis scales denser, basalmost pair of pinnae hastate and with bases somewhat cordate, while the latter has stipe and rachis scales much sparser, basalmost pair of pinnae oblong and with bases cuneate.

Plants perennial, evergreen, 20–36 cm tall. Rhizome erect, short, rhizome apex and stipe base densely covered with scales; stipe slightly green, 4–8 cm long, 0.6–0.8 mm diam., adaxially sulcate; scales deltoid-lanceolate to lanceolate, 1.2–4.8 × 0.6–2.8 mm, papery, brown, margins entire or with short teeth, apex acuminate to caudate, distal stipe scales similar but narrower and shorter, linear to lanceolate, 0.5–3.2 × 0.1–1.5 mm, membranous, edges transparent, apex long-caudate; scales with central cells long-rectangular and each side substraight, marginal cells irregularly curved. Leaves 1-pinnate, 12–36 per rhizome, green, nearly oblanceolate, 16–26 cm long, base slightly contracted, apex deeply pinnatifid-acuminate. Rachis light green, adaxially sulcate, densely scaly; scales linear, brown; no proliferous bulbils. Pinnae 18–36 pairs, alternate or some basal pinnae subopposite, sessile or lower pinnae short-stalked, often covered with white lime dots, sparsely scaly on two sides or abaxially only; microscales linear to lanceolate, nearly 0.2 mm long; basal basiscopic pinna margins forming an angle of (60–)90° with rachis, lower pairs 1.0 cm long, 8 mm wide at base, apices nearly rounded; basalmost pairs of pinnae deltoid, bases slightly cordate, two sides of midrib nearly symmetric, basal acroscopic and basiscopic sides auriculate; middle pinnae alternate, oblong, 1.3 cm long, 8 mm wide at base, base asymmetric, basal acroscopic side auriculate and auricles deltoid with acute apex, acroscopic margins nearly entire, repand or shallowly serrulate, proximal basiscopic margins entire, distal basiscopic margins with 2 or 3 shallow obtuse teeth; frond texture papery; venation pinnate, visible adaxially and obviously raised abaxially, pinnate above midrib from base upward, simple or dichotomous below midrib, veinlets rarely twice dichotomously branched. Lower 5–9 pairs sterile; sori terminal on veinlets, ca. 8 mm from pinna margins, 1–9 above midrib, 0–4 below midrib, ca. 1 mm in diam.; indusia peltate, margins shallow toothed, membranous, light brown to darkly brown, nearly falling off when mature.

Geographical distribution:— Polystichum hastipinnum is only known from the type locality in Luokeng National Reserve, Shaoguan city, Guangdong Province, South China.

Ecology:— Polystichum hastipinnum was observed to grow on the limestone walls of a wet cave at an elevation of ca. 220 m.

IUCN Red List category:—The only population known is from the type locality and comprises 60 plants. Tourism in the reserve seriously threatens the survival of the species. The status of the new species should be CR–Critically Endangered category based on current information and following IUCN (the International Union for Conservation of Nature and Natural Resources) guidelines ( IUCN 2015).

Etymology:—From the Latin, hasti-, hastate, and -pinnum, pinnae, referring to the hastate basalmost pinnae.

Additional specimens examined (paratypes):— CHINA. Guangdong Province: Shaoguan city, Luokeng Zhen, Zengwu, close to Luokeng Lake , 24°31’35’’N, 113°21’06”E, in a limestone cave, elev. ca. 220 m, 4 Jun. 2016, Guang-Da Tang LK024 ( CANT!) GoogleMaps , 11 Sept. 2016, LK0911 ( CDBI!, MO!) GoogleMaps