Bulbophyllum tianguii K.Y.Lang & D.Luo, J. Wuhan Bot. Res. 25: 558 (2007); Chen & Vermeulen, 2009, Flora of China 25: 424; Zhou et al., Updated Checklist Orch. China: 22 (2016) (Fig. 2)

Type:— CHINA. Guangxi, Leye, Huapingzen, Yachang orchid nature reserve, on the rock, alt. 970 m a.s.l., 2007, Liu S. Y. & Deng Z. H . 010 (PE 01432249, PE 01432250, PE 01432251) .

Note. The discovery of this species in northern Vietnam is quite expected, due to the area of Ha Giang Province has similar habitat conditions observed in Guangxi where the species was firstly found. In the original description the authors did not mention the triangular acute teeth on the upper margin of stelidia, which are clearly seen in Vietnamese plants.

Species examined: — VIETNAM, Ha Giang Province, Dong Van District, lithophyte on mossy rocks at about 1400 m a.s.l. 24 March 2022 Truong Ba Vuong, Bui Van Huong, BV 1350 (VNM 00069943), 24 March 2022 Truong Ba Vuong, Bui Van Huong, BV 1352 (VNM 00069939), 24 March 2022 Truong Ba Vuong, Bui Van Huong, BV 1353 (VNM 00069940), 24 March 2022 Truong Ba Vuong, Nguyen Van Canh, BV 1351 (VNM 00069944) .

Analytical photos: — VIETNAM, Ha Giang Province, Dong Van District, lithophyte on mossy rocks at about 1400 m a.s.l. 24 March 2022 Truong Ba Vuong, Bui Van Huong, BV 1350 (VNM 00069943), 24 March 2022 (VNM 00069944) – LE 01123074 (https://en.herbariumle.ru/?t=occ&id=132345) .