Gastrochilus prionophyllus is similar to G. distichus and G. corymbosus, but could be distinguished by having thick fleshy leaves and distinct serrate at the leaf margin, smaller flowers, reniform epichile with dentations at the margin and thickened cushion on the central epichile, and subconic hypochile.

CHINA. Yunnan Province: Malipo County, Xia jinchang town, limestone forest, 1550–1650 m a.s.l., epiphytic on tree trunks or on rocks, 15 Mar. 2016, Qiang Liu 359 (holotype, HITBC!)

Epiphytic herbs, stem pendulous, 10–15 cm long, ca. 1.25 mm in diameter, slender, unbranched with tiny red-purple spots. Leaves alternate, distichous, ovate, 0.9–1.3 × 0.3–0.5 cm, margin significantly serrate; leaf apex acuminate with 2 unequally awns; abaxial leaves with purple spots and sometimes on the adaxial leaves. Inflorescences several, opposite to leaves, subumbellate, 2–3-flowered; peduncle 0.9–1.1 cm, slender, upper part enlarged, lower part with 2 cupular sheaths; floral bracts ovate-lanceolate, 1.0–1.2 mm; pedicel and ovary 0.9–1.1 cm. Flower yellow-green, with reddish brown spots. Dorsal sepal concave, oblong-elliptic, 3.4–3.7 × 2.3–2.6 mm, apex obtuse; lateral sepal concave, oblong-elliptic, 3.6–4.2 × 2.6–3.0 mm, apex obtuse; petals subobovate, 3.5–4.1 × 2.3–2.5 mm, apex obtuse. Lip with an epichile and a saccate hypochile; epichile nearly reniform, 2.8–3.3 × 4.9–5.3 mm, adaxially glabrous, with a thicken central cushion and 2 conic calli near base, margin irregularly denticulate; hypochile subconic, laterally compresses, 5.0–5.7 mm tall, 4.5–5.0 mm in diameter, apex rounded. Column stout, ca. 2.5 mm long; anther cap narrowed into a beak toward apex; rostellum bilobed with acuminated tip, and arising a horn-like awn from the center of each lobe (obvious in the lateral view).

The specific epithet refers to the significantly serrate margin of leaf blades.

At present, the new species is only to be found in Malipo town, Yunnan, China. It was also recorded in Ha Giang province of North Vietnam according to Prof. L.V. Averyanov’s comment. Gastrochilus prionophyllus was found on the tree trunks at altitudes from 1550 to 1650 m in the limestone broad-leaved forests, which is dominated by Quercus marlipoensis Hu & W. C. Cheng (Fagaceae), Q. utilis Hu & W. C. Cheng (Fagaceae), Platycarya strobilacea Siebold & Zuccarini (Juglandaceae), Manglietia grandis Hu & W. C. Cheng (Magnoliaceae), Eriobotrya japonica (Thunberg) Lindley (Rosaceae) and Podocarpus macrophyllus (Thunberg) Sweet (Podocarpaceae), as well as an abundance of other orchid species, including Eria coronaria (Lindley) H. G. Reichenbach (Orchidaceae), Paphiopedilum malipoense S. C. Chen & Z. H. Tsi (Orchidaceae) and Habenaria fordii Rolfe (Orchidaceae).

Gastrochilus prionophyllus was observed in flowering from March to April in the wild.

ju ye pen ju lan (锯叶盆距兰)

CHINA. Yunnan: Malipo County, Xia jinchang town, limestone forest, 1600m a.s.l., 4 Mar. 2016, Qiang Liu 214 (paratype, HITBC!); China. Yunnan. Malipo County, Babu village, limestone forest, 1650m a.s.l., 16 Jul. 2016, Qiang Liu 376 (HITBC!)

At present, Gastrochilus prionophyllus is only known from two sites (Malipo County: Xia jinchang town and Babu village), around 50 individuals were discovered based on two years of botanical surveys. Although limestone forests have been seriously threatened by modern destructive human activities, not limited to quarrying and rubber plantation expansion (Sodhi and Brook 2006; Liu et al. 2015), the distribution of the new species lies in the landmine zone, a legacy from the Sino-Vietnamese War and the restricted zone keeps the habitat of limestone forest intact in Malipo county. Therefore, we expect that more individuals could be found in the adjacent forests extending along the China-Vietnam border. We suggest that the current conservation status of this new species is Data Deficient (IUCN 2017).