Arachniodes quangnamensis Li Bing Zhang, Ngan Thi Lu & Liang Zhang 2018, sp. nov.
Creators: name: Lu, Ngan Thi
name: Zhang, Liang
name: Zhou, Xin-Mao
name: Gao, Xin-Fen
name: Zhang, Li-Bing
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Polypodiopsida
Polypodiales
Dryopteridaceae
Arachniodes
Arachniodes quangnamensis

description: Arachniodes quangnamensis Li Bing Zhang, Ngan Thi Lu & Liang Zhang, sp. nov. Figs. 1A ‒ H & 3A ‒ C, H, I & L.
Type:— VIETNAM. Quangnam Province: Songthanh Nature reserve, elev. 400–460 m, 5 December 2014, Li Bing Zhang, Liang Zhang & Ngan Thi Lu 7926 (holotype VNMN!, isotypes CDBI!, MO!).
Diagnosis:—This species resembles Arachniodes dimorphophylla (Hayata 1911: 428) Ching (1962: 257) in having fronds dimorphous, fertile fronds lanceolate, longer but narrower than sterile fronds, sterile fronds ovate-lanceolate, and sori small (1.5–2 mm in diam.) and closer to midribs than to segment margins, but the former bears rhizomes suberect or ascending (creeping rhizomes unseen), laminae more shallowly dissected, often 2-pinnate-pinnatifid, basal basiscopic segments of lowest pinnae less elongated, and indusia ciliate; in contrast, the latter has rhizomes often short-creeping, laminae 3-pinnate, basal basiscopic segments of lowest pinnae longelongated, and indusia entire.
Rhizome erect or ascending, 1.2–4.2 × 1.2–2.5 cm, with remnant bases of old stipes, up to 18 fronds each rhizome; ca. 35 roots, 3–10 cm × 0.3–0.7 mm, apex densely scaly; scales (brown to red-brown), linear-narrow lanceolate, tip tortuous, 4–10 × 0.3–1.0 mm, entire, membranous. Fronds dimorphic, 21–75 cm. Sterile lamina 14–32 × 5–18 cm, stipe 7–29 cm × 3.2–12 mm, base with scales similar to those on rhizome, scales sparser upward, blackish, thread– linear, 4–6 × 0.12–0.6 mm, entire and thicker; lamina 2 pinnate-pinnatifid, green when dried, deltoid-lanceolate, papery, base acute, apex acuminate; rachis scaly as distal portion of stipe, sparse scales adaxially; pinnae 12–22 pairs, lowest pinnae 4–14 × 2–5.5 cm, stalks ca. 0.7 cm, upper shorter even sessile, alternate, spreading, lanceolate or deltoid-lanceolate, base rounded or broadly cuneate, apex acute or obtuse; pinnules 5–14 pairs per pinna, shortly stalked, oblong, deltoid-lanceolate, sometimes elliptical-oval, 1.0–1.5 × 1.5–3.8 cm, base acroscopically rounded, obtuse, cuneate basiscopically cuneate, apex obtuse, margin often aristate; costule, vein sparse minute brown filiform scales abaxially. Fertile fronds up to 75 × 4–12 cm; lamina similar to that of sterile fronds in shape and dissection, often longer than sterile but narrower, papery to subleathery; pinnae 12–24 pairs, lowest pinnae 4–11.2 × 1.8–3.2 cm, lanceolate, alternate, base acute, oblique-cordate, apex acute or acuminate; pinnule 8–13 pairs, lanceolate or oblong, 0.5–1.0 × 1.0– 2.8 cm, base acroscopically truncate, obtuse, basiscopically cuneate, apex obtuse, margin lobed or pinnatifid, mucronate teeth. Sori small (ca. 2.0 mm), terminal on veinlets, approximate, 2–9 pairs per ultimate segment, closer to midvein than margin; spores elliptical type, 31–38 × 35–46 um, inflated, echinate folder; indusia brown to dark brown, membranous, ciliate or irregularly denticulate on margin (ca. 2.4 mm).
Etymology:— From quangnam, the province name in central Vietnam, and the Latin ending -ensis, of origin, referring to the type locality where we collected the plant.
Distribution:— This species is currently only known from the type locality and probably is endemic to Central Vietnam.
Notes:— In addition to Arachniodes quangnamensis, there are two more species in the genus with dimorphic fronds: A. hainanenis (Ching 1934: 44) Ching (1962: 258) (type: Hainan, China) and A. dimorphophylla (type: Okinawa, Japan). Phylogenetically, A. quangnamensis was resolved as sister to A. hainanensis, while the Japanese dimorphic species was nested in other clade (Lu et al., submitted). He et al. (2013) noted a dimorphic species reported from Taiwan, which needs to be confirmed.
Additional material examined:— VIETNAM. Quangnam Province: Songthanh Nature Reserve, elev. 400–460 m, 5 December 2014, Li Bing Zhang, Liang Zhang & Ngan Thi Lu 7915, 1918 (CDBI!, MO!, VNMN!).
description: Published as part of Lu, Ngan Thi, Zhang, Liang, Zhou, Xin-Mao, Gao, Xin-Fen & Zhang, Li-Bing, 2018, Three new species of the fern genus Arachniodes (Dryopteridaceae) from Vietnam, pp. 126-132 in Phytotaxa 376 (3) on pages 130-131, DOI: 10.11646/phytotaxa.376.3.1, http://zenodo.org/record/13726654