Arachniodes longicaudata Li Bing Zhang, N.T. Lu & Liang Zhang, 2018

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, Phytotaxa 376 (3), pp. 126-132 : 130

publication ID	https://doi.org/ 10.11646/phytotaxa.376.3.1
DOI	https://doi.org/10.5281/zenodo.13727295
persistent identifier	https://treatment.plazi.org/id/E078202E-2830-4718-AE85-520EFD6FF8EB
treatment provided by	Felipe
scientific name	Arachniodes longicaudata Li Bing Zhang, N.T. Lu & Liang Zhang
status	sp. nov.

Treatment

Arachniodes longicaudata Li Bing Zhang, N.T. Lu & Liang Zhang View in CoL , sp. nov. Figs. 2 View FIGURE 2 & 3 View FIGURE 3 : D, E, J, K & N.

Type:— VIETNAM. Nghean Province: Pumat National park, elev. 350 m, 29 October 2014, Li Bing Zhang, Liang Zhang & Ngan Thi Lu 7189 (holotype VNMN!, isotypes CDBI!, MO!).

Diagnosis:—This species resembles Arachniodes chinensis ( Rosenstock 1914: 30) Ching (1962: 257) by having laminae 2-pinnate and deltoid, pinnae slightly oblique deltoid to lanceolate, and pinnules lanceolate or oblong, but the former has rhizomes ascending, lamina apex caudate, with a conform terminal pinna, sori closer to the segment margins than to the midrib, and indusia ciliate; in contrast, the latter has rhizomes creeping, lamina apex acuminate, sori medial between midvein and margin or closer to midvein, and indusial often entire.

Rhizome erect, ascending, small, ca. 1.5 × 1.0 cm, with remnant bases of old stipes, 5–7 fronds in one plant; ca. 15 roots, 2–14 cm × 1.6 mm, apex densely scaly; scales fragile often break, brown to dark brown, filiform to lanceolate, 1.6–8 × 0.4–1.0 mm, entire, membranous. Frond 22–66 cm, stipe 14–34 cm × 4–8 mm, base densely scaly with scales similar to those on rhizome, upward scales appressed, filiform-linear, 1.0–8 × 0.3–0.8 mm, but blackish, thicker, based or round attached with upper part entire, lower part margin sparse hairlike or irregular denticulate. Lamina 2- pinnate, often longer than stipe, dull green when dried, deltoid somewhat as triangular or deltoid-lanceolate, 8–32 × 9.5–23 cm, thinly papery to papery, base cordate, rounded-truncate, or broadly cuneate, apex abruptly caudate with a stalked conform terminal pinna, apex very long up to 20 cm and bigger than lateral pinnae (larger any pinnae); rachis abaxially and adaxially scaly as distal portion of stipe scales; pinnae 1–(2)–3–(4) pairs, lowest pinnae lanceolate, 5–13 × 2.2–5 cm, alternate, lower 1 (or 2) pairs opposite with short stalk 0.2–0.5 cm, base cordate, rounded-truncate, or broadly cuneate, apex acuminate; pinnules 6–14 pairs, very short stalked or sessile, lanceolate or oblong, 2.5 × 1.4 cm, base acroscopically rounded, broad cuneate (broad acute), obtuse, basiscopically cuneate, apex acute or obtuse, margin mucronate or aristate; costule, veins of ultimate segments with minute brown linear-subulate appressed scales abaxially. Sori, 2.8–4 mm, terminal on veinlets, 2–11 pairs per ultimate segment, close to margin; spores subglobose to elliptical type, 31–36 × 43–45 um, inflated, irregular echinate folder; indusia, 1.2–2.4 mm, dark brown, firmly membranous, subentire, long ciliate as hairlike.

Etymology:— The specific epithet refers to long caudate apex of the species

Distribution:— This species is currently known from North-Central Vietnam.

Notes:— Arachniodes longicaudata morphologically also resembles A. yaoshanensis (Y.C. Wu 1932: 78) Serizawa (1973: 219) by having long caudate lamina apex, lowest pinnae not elongated, but the former has fewer pinnae sometimes lamina triangular, scales not blackish, and sori closer to segment margins. Phylogenetically, A. longicaudata was resolved as sister to A. nigrospinosa (Ching 1931: 191) Ching (1962: 258) whose type is from Guangdong, China (Lu et al., submitted).

Arachniodes longicaudata is not rare in Vietnam and can be found in the North (Bavi, Langson, Tamdao) and in the Central (Nghean, Quangbinh, Quangtri) Vietnam.