Chamaeanthus averyanovii Vuong, Kumar, V.H. Bui, V.S.Dang, sp. nov. (Fig. 1)

Type:— VIETNAM. Son La Province: Thuan Chau District, 18 June 2021, Truong Ba Vuong, Bui Van Huong, BV 1194 (VNM 00069908!)

Etymology:—The specific epithet honors Prof. Leonid Averyanov for his outstanding contribution to the orchid science in Asia.

Description. Miniature clustered epiphyte. Stem ca. 5 mm long, covered with distichous leaf sheaths. Leaves fleshy, oblong, slightly concave and falcate, 3–4 cm long, 5–7 mm wide, acute, unequally 2-lobed at the apex, sheathed at the base, sheaths ca. 7 mm long embracing the stem. Inflorescence spike, arising from lower leafless part of the plant, glabrous; peduncle green, terete, 6–7 mm long, with 1 to 4 distantly bracts; rachis clavate, ca. 11 mm long; flowers up to 15, with 1–3 flowers blooming at the same time, not open widely; floral bract green, concave, narrowly triangular, ca. 2 mm long, acuminate; pedicel with ovary faintly greenish-white, glabrous, ca. 2 mm long, terete; tepals white, sub-similar, pale yellow towards the apex, lip white, pale yellow at the base. Dorsal sepal narrowly elliptic, 5–5.5 mm long, 1.5 mm wide, tapering to caudate at the apex; lateral sepals narrowly elliptic, 5.5–6 mm long, 1.5 mm wide, tapering at the apex. Petals narrowly elliptic, 4.5–5 mm long, 1 mm wide, tapering at the apex. Lip 3-lobed, spur absent, glabrous, conical in outline shaped, attached to column foot by a small appendage; midlobe conical, ca. 2.5–3 mm long, entire, apex pugioniform; side lobes erect, rectangular, ca. 1.2 mm long, 1 mm wide, margin irregularly dentate. Column ca. 1 mm long, lower margin with triangular wing; column foot as long as or slightly longer than ovary, oblique, ca. 1.1 mm long; anther cap helmet shape, ca. 1mm long; pollinia 2, subglobose. Fruit not seen.

Habitat and phenology:—Epiphytic on small tree branches on canopy. Flowering in June to July.

Distribution:— Vietnam (Son La Province), endemic

Additional specimens studied: MALAYSIA:— Chamaeanthus brachystachys August 190, R. Schlechter s.n. (Isosyntype, AMES00106675)

Notes:— C. averyanovii looks similar to C. brachystachys and C. canhii, however, they are different. The comparative account is presented in Table 1.

Morphological data of C. brachystachys is based on Schlechter (1905) and Pridgeon et al. (2014): t. 636.1 by Judi Stone, from KEW spirit collection: Borneo, 1989 A. Lamb AL1154/89 (number 56439)