Hymenasplenium denticulatum K.W. Xu, Li Bing Zhang & W.B.Liao, 2018

Hymenasplenium denticulatum K.W. Xu, Li Bing Zhang & W.B.Liao View in CoL , sp. nov. Fig. 3 View FIGURE 3 .

Type:— CHINA. Guizhou: Daozhen County, Baijishan, elev. 750 m, on wet palisades near streams, 16 October 15, Zhengyu Liu 16082 (holotype MO! isotype MO! ).

Diagnosis:— Hymenasplenium denticulatum is most similar to H. murakami-hatanakae Nakaike (1992: 841) in having pinnae falcate to trapeziform and usually ascending, sori supramedial to (sub)marginal, but the former has plants 30–50 cm tall, marginal teeth of the pinnae shallow (0.5–1 mm), dense, and usually shallowly retuse, and veins usually terminating in the notches, or terminating in the marginal teeth, while the latter has plants 25–40 cm tall, marginal teeth of the pinnae deep (1 mm at base), sparse, acute, not retuse, and veins terminating in marginal teeth.

Plants perennial, evergreen, 30–50 cm tall. Rhizomes long creeping, ca. 3 mm in diam., apex scaly, scales brown, narrowly triangular, margins nearly entire, 1 × 0.25 mm; root brown when dried, slender, up to 4 cm long, rhizome and root glabrous or covered with yellowish brown woolly indument. Fronds remote, 10–20 mm apart, herbaceous; petioles dark brown, glabrous, 15–25 cm long. Laminae narrowly ovate, 1-pinnate, 15–25 × 4–6 cm, base deflexed, slightly reduced, widest near middle, gradually narrowing toward apex, apex acuminate; rachises 1 mm in diam., glabrous, adaxial side grooved and with 2 green narrow wings. Pinnae shortly stalked to almost sessile at apex, 20–30 pairs, subopposite or alternate, falcate to trapeziform, (middle pairs) 2–3.5 × 0.6–1 cm, up to 3–5 mm apart, base asymmetrical, acroscopic side truncate and subparallel or overlapping with rachis, with ca. 10 mm absent (calculated from the base to the first tooth appearing in the margin of basiscopic side), acroscopic margins serrate, teeth shallow and dense, usually retuse, basiscopic margins deep and sparse, teeth obtuse and not retuse, apex acute or acuminate. Veins visible on both sides of pinnae, stramineous, lateral veins visible on both sides of pinnae, green, forking and terminating in notches or marginal teeth, 2–3 basal basiscopic veins lacking. Sori linear, 1–3 mm long, supramedial to (sub)marginal, (2–)6–8 on acroscopic side and 4–6(–8) on distal basiscopic side of the pinnae in the middle part of the laminae, centers 1–2 mm apart from one another; indusia brown, linear, membranous, entire, opening toward costa.

Geographical distribution:— Hymenasplenium denticulatum is currently only known from the adjacent Chongqing and northern Guizhou. It is likely endemic to Southwest China.

Ecology:— Hymenasplenium denticulatum was observed to grow on wet palisades near streams.

Etymology:—The species epithet is based on the Latin adjective, denticulatum , denticulate, referring to the denticulate pinna margins of the new species.

Vernacular name:— àŵůďäffǎ (xi chi mo ye tie jiao jue).

Taxonomic notes:— Hymenasplenium denticulatum can be easily distinguished by its shallow and dense marginal teeth, usually retuse at apex, and supramedial to (sub)marginal sori. In addition, it is likely to be endemic to Southwest China, while the morphologically similar species H. murakami-hatanakae is only distributed in Japan, Taiwan Island based on our large-scale phylogenetic study ( Xu et al. 2018a).

Additional material examined:— CHINA. Chongqing: Nanchuan, Jinfoshan Mt. , elev. 800 m, 5 April 1996, Zhengyu Liu 15536 (MO!) ; 14 October 1995, Sirong Yi 15799 (MO!) .