Oricymba gongshanensis sp. nov. (Cymbellaceae; Bacillariophyceae), a new species from southwest China Author Guo, Ji-Shu 0000-0002-3052-1726 Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, P. R. China. & 1261797177 @ qq. com; https: // orcid. org / 0000 - 0002 - 3052 - 1726 1261797177@qq.com Author Meng, Wen-Wen 0000-0002-4283-8202 Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, P. R. China. & mengww 1996 @ 163. com; https: // orcid. org / 0000 - 0002 - 4283 - 8202 Author He, Xiao-Yang 0000-0003-0190-7563 Gong-shan Administration Bureau, Gao-li-gong Mountain National Nature Reserve, Gongshan 673500, China. & hexiaoy 001 @ 126. com; https: // orcid. org / 0000 - 0003 - 0190 - 7563 Author Zhang, Yun 0000-0002-9455-4711 Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, P. R. China. & zhangyun @ ynu. edu. cn; https: // orcid. org / 0000 - 0002 - 9455 - 4711 zhangyun@ynu.edu.cn Author Li, Yan-Ling 0000-0002-3540-8706 Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, P. R. China. & yanlingli @ ynu. edu. cn; https: // orcid. org / 0000 - 0002 - 3540 - 8706 yanlingli@ynu.edu.cn Author Kociolek, John Patrick 0000-0001-9824-7164 Museum of Natural History and Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado- 80309, USA. & patrick. kociolek @ colorado. edu; https: // orcid. org / 0000 - 0001 - 9824 - 7164 patrick.kociolek@colorado.edu text Phytotaxa 2021 2021-06-18 508 1 39 48 http://dx.doi.org/10.11646/phytotaxa.508.1.3 journal article 10.11646/phytotaxa.508.1.3 1179-3163 5425768 Oricymba gongshanensis J.-S. Guo & Y.-L. Li, sp. nov. (Figs 1–19) LM (Figs 1–9): Valves linear-lanceolate, nearly symmetrical to slightly asymmetrical about the apical axis, with a moderately inflated central portion gradually tapering or nearly parallel to bluntly-cuneate poles. Length 46.5–64.5 μm, width 10.5–12.3 μm, length/width ratio 4.4–5.2, median 5.0 (n = 30). Raphe filiform near the central area, becoming lateral, with external raphe fissures somewhat undulate, internal raphe fissures straight. External proximal raphe ends expanded, deflected towards the ventral side. External distal raphe fissures hooked towards dorsal margin. Axial area lanceolate. Central area rhombic-lanceolate, extremely asymmetrical, occupying nearly 1/3 of the valve width, with 1–4 slightly shortened central dorsal striae, 3–8 markedly shortened central ventral striae. Distinct isolated stigma lies between the protruding central nodule and the two central striae on the ventral side. Striae biseriate, with dorsal striae almost parallel at the valve centre, becoming slightly radiate towards the poles, ventral striae slightly radiate throughout, 7–11 in 10 μm. Areolae visible, 66–100 in 10 μm. SEM: Valve exterior (Figs 10–16): raphe undulate with proximal raphe ends slightly dilated, weakly bent ventrally (Figs 15, 16), distal fissures hooked, deflected towards the dorsal side (Figs 12–14). Striae biseriate, occasionally uniseriate adjacent to the axial area (Figs 12–15). Areolae mostly rounded or elliptical, occasionally elongate rectangular openings (Figs 12–16). Areolae may contain small occlusions (Fig. 16). Longitudinal ridges are very thick along the valve margins except near the valve terminus with distinct and shallow grooves along both the valve face and mantle edges (Figs 10, 11). Apical pore fields present at both ends on the mantle and clearly physically separated and morphologically distinct from the areolae (Figs 12–14). Valve interior (Figs 17–19): striae formed by rounded-elliptical, biseriate, occasionally elongate areolae separated by robust silica ribs (Figs 17–19). The internal raphe continuous without intermissio (Figs 17, 19), distal raphe ends offset, bent slightly towards the dorsal margin, and terminate in small, knob-like helictoglossae (Fig. 18). Two internal, narrow, slit-like stigma openings on the ventral side occluded by fine ingrowths from the perimeter (Fig. 19). The dentate occlusions of areolae are evident from the interior (Figs 17–19). Type:— CHINA . Yunnan Province : Gongshan country, Gaoligong Mountain , GS 1, 27°46′44″ N , 98°27′49″ E , elevation 3200 m a.s.l. , samples collected by Prof. Yan-Ling Li , 9 August 2019 . Holotype GS 2019080901 in Coll. Yan-Ling Li , Yunnan University , Kunming , China. Figure 1 is of the holotype . Etymology: — gongshanensis , referring to the type locality from which the new species was described. Ecology:— Oricymba gongshanensis is known only from a stone wall, situated at 3200 m a.s.l. This species was associated with Achnanthidium minutissimum (Kützing) Czarnecki ( Czarnecki 1994: 157 ) , Staurosira venter (Ehrenberg) Cleve & Möller (1877: 242) , Gomphonema gracile Ehrenberg (1838: 217) , Oricymba xianjuensis W. Zhang & Kociolek (2016: 135) , Encyonema minutum (Hilse) Mann (in Round et al. 1990: 167 ), and several at present unidentified species of Fragilaria Lyngbye (1819: 182) , Cymbella, Gomphonema Ehrenberg (1832: 87) and Encyonema Kützing (1833: 589) .