New orchids in the flora of Vietnam VIII (Orchidaceae: Epidendroideae, tribes Malaxideae, Neottieae and Podochileae) Author Averyanov, Leonid V. 0000-0001-8031-2925 Komarov Botanical Institute of the Russian Academy of Sciences, 2, Prof. Popov Street, 197022, St. Petersburg, Russia av_leonid@mail.ru Author Nguyen, Van Canh 0000-0001-9578-0342 Institute of Applied Technology, Thu Dau Mot University, No. 6, Tran Van On Street, Phu Hoa Ward, Thu Dau Mot City, Binh Duong Province, Vietnam nguyenvancanh@tdmu.edu.vn Author Vuong, Truong Ba 0000-0003-3452-8455 Institute of Tropical Biology, Vietnam Academy of Science and Technology, 85, Tran Quoc Toan Street, District 3, Ho Chi Minh City, Vietnam bavuong2019@yahoo.com Author Nuraliev, Maxim S. 0000-0001-8291-2633 Department of Higher Plants, Biological Faculty, M. V. Lomonosov Moscow State University, 1, 12, Leninskie Gory, 119234, Moscow, Russia & Joint Russian-Vietnamese Tropical Scientific and Technological Center, 63, Nguyen Van Huyen Street, Cau Giay District, 122000, Hanoi, Vietnam max.nuraliev@gmail.com Author Nguyen, Khang Sinh 0000-0001-5171-4140 Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, 18, Hoang Quoc Viet Road, Cau Giay District, Hanoi, Vietnam & Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18, Hoang Quoc Viet Road, Cau Giay District, Hanoi, Vietnam nskhang@gmail.com Author Maisak, Tatiana V. 0000-0001-5919-6755 Komarov Botanical Institute of the Russian Academy of Sciences, 2, Prof. Popov Street, 197022, St. Petersburg, Russia tmaisak@mail.ru Author Yudova, Daria A. 0000-0002-3214-5795 Komarov Botanical Institute of the Russian Academy of Sciences, 2, Prof. Popov Street, 197022, St. Petersburg, Russia gloomy_lars@mail.ru Author Saidov, Nikita T. 0000-0002-3940-6628 Komarov Botanical Institute of the Russian Academy of Sciences, 2, Prof. Popov Street, 197022, St. Petersburg, Russia nick-saidov@yandex.ru Author Nguyen, Cuong Huu 0000-0003-2281-741X Vietnam National University of Forestry, Xuan Mai, Chuong My, Hanoi, Vietnam nguyenhuucuong.tvr@gmail.com Author Nong, Duy Van 0000-0002-1509-4412 Tay Nguyen Institute for Scientific Research, Vietnam Academy of Science and Technology, Da Lat, Vietnam nongvanduy07@yahoo.com.vn text Phytotaxa 2024 2024-07-02 658 1 1 49 http://dx.doi.org/10.11646/phytotaxa.658.1.1 journal article 10.11646/phytotaxa.658.1.1 1179-3163 13217417 Oberonia Lindley (1830: 15) Oberonia maxima C.S.P.Parish ex Hooker (1888: 677) , Seidenfaden (1968: 21 , 1975b: 79 , 1978: 13 ), Ansari & Balakrishnan (1990: 22) , Pearce & Cribb (2002: 233) , Averyanov et al. (2016: 29) , Geiger (2016: 391) pro parte, Averyanov & Gruss (2017: 28) , Bunpha et al. (2019: 121) pro parte, Kaliamoorthy & Saravanan (2019: 319) , Aung et al. (2020: 92) , Ormerod et al. (2021: 175) , Bunpha & Pedersen (2022: 887) pro parte. ( Fig. 12D–F ) Lectotype (designated by Seidenfaden (1978: 13)) :— MYANMAR . Mon State : Mawlamyine District , C . S . P . Parish 287 ( K K000387694 photo!). Ecology and phenology in Vietnam : —Clustering epiphyte. Primary and old secondary humid evergreen broad-leaved submontane forests on granite and sandstone at elevations of 700–1500 m a.s.l. Rare. Flowers in September–October. Distribution: — Vietnam : provinces Dien Bien (Muong Nhe District) and Lam Dong (Lac Duong District). NE India , Myanmar , Thailand , Laos . Conservation status in Vietnam : —Two localities of Oberonia maxima , which are more than 1100 km apart from each other, are known in the country. Available information on the species populations in both locations is very scarce. However, wide deforestation and land exploitation for agriculture in both areas surely lead to a dramatic decrease in the possible extent of the species habitats and their quality. Based on these observations, we estimate the national conservation status of the species as Near Threatened (NT). The conservation status of this species outside Vietnam has never been evaluated. Meanwhile, in a locality in Laos documented by Averyanov et al. (2016) , this species was observed to be fairly common, which points to a Least Concern (LC) status. Notes: — Oberonia maxima is remarkable within the genus in its unusually large habit. It distinctly differs from the morphologically close O. integerrima Guillaumin (1955: 692) also occurring in Eastern Indochina ( Chen et al. 2009 , Averyanov 2013 , Jin et al. 2023 ) in commonly twice longer leaves (usually longer than 7–8 cm vs. 5–21 cm long), in less dense inflorescence appearance with sepals and petals partially exposed, being only partially overlapped by lips of more basal flowers (vs. inflorescence very dense, with sepals and petals entirely obscured by the overlapping lips) and lip orbicular to orbicular triangular, emarginate at apex and erose-denticulate along the margin (vs. lip reniform to broadly reniform, round at apex, with entire straight to inconspicuously erose margin). Taking these differences into account, we treat O. integerrima as a distinct species, despite it was synonymized with O. maxima by Geiger (2016) , Bunpha et al. (2019) and Bunpha & Pedersen (2022) . Studied specimens:— VIETNAM . Dien Bien Province : Muong Nhe District, Muong Nhe Natural Reserve, Sin Thau Municipality, A Pa Chai Village, around point about 22º22’50’’N 102º14’18”E , old humid secondary evergreen broad-leaved submontane forest on steep mountain slopes composed with sandstone at elevations of 750–820 m a.s.l. along small stream, epiphyte on tall tree, occasional, 16 May 2022 , herbarium prepared on 4 October 2022 , flowers uniform light green, L. Averyanov, T. Maisak, VR1681 (LE LE01169539 https://en.herbariumle.ru/?t=occ&id=144129, photos LE LE01123561 https://en.herbariumle.ru/?t=occ&id=143254). VIETNAM . Lam Dong Province : Lac Duong District, forest around Da Nhim, flowers green, median lobe almost rounded, apex rounded or slightly retuse, margin dentate, 6 October 2020 , Truong Ba Vuong, Ngo Quang Dang, BV889 (photos LE LE01088171 http://en.herbariumle. ru/?t=occ&id=43686).