One new species of Achnanthidium Kützing (Bacillariophyta, Achnanthidiaceae) from Tibet, China Author Ge, Danyang 0000-0003-2904-0260 College of Life Science and Technology, Harbin Normal University, Harbin, 150025, China & gdy 18846166215 @ 163. com; https: // orcid. org / 0000 - 0003 - 2904 - 0260 Author Zhang, Simeng 0000-0001-9461-2646 College of Life Science and Technology, Harbin Normal University, Harbin, 150025, China & zhangsm 147 @ 163. com; https: // orcid. org / 0000 - 0001 - 9461 - 2646 Author Liu, Hongyan 0000-0003-1960-6806 College of Life Science and Technology, Harbin Normal University, Harbin, 150025, China & tgzy 1632021 @ 163. com; https: // orcid. org / 0000 - 0003 - 1960 - 6806 Author Liu, Yan 0000-0001-8556-5040 College of Life Science and Technology, Harbin Normal University, Harbin, 150025, China & yanliuhrb @ hotmail. com; https: // orcid. org / 0000 - 0001 - 8556 - 5040 yanliuhrb@hotmail.com Author Kociolek, Patrick John 0000-0001-8556-5040 Museum of Natural History and Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, U. S. A. Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China & patrick. kociolek @ colorado. edu; https: // orcid. org / 0000 - 0001 - 8556 - 5040 patrick.kociolek@colorado.edu Author Zhu, Huan 0000-0002-8531-2067 huanzhu @ ihb. ac. cn; https: // orcid. org / 0000 - 0002 - 8531 - 2067 huanzhu@ihb.ac.cn Author Liu, Guoxiang 0000-0001-8565-2363 liugx @ ihb. ac. cn; https: // orcid. org / 0000 - 0001 - 8565 - 2363 liugx@ihb.ac.cn Author Fan, Yawen 0000-0001-9969-5428 College of Life Science and Technology, Harbin Normal University, Harbin, 150025, China & fanyaw @ 163. com; https: // orcid. org / 0000 - 0001 - 9969 - 5428 text Phytotaxa 2022 2022-03-09 538 4 268 280 journal article 20250 10.11646/phytotaxa.538.4.1 82dc7ea9-e911-4675-8c59-797222354a47 1179-3163 6340368 Achnanthidium tibeticum Y. Liu & J.P. Kociolek sp. nov. Figures 1–32 Type:­— CHINA . Tibet: Medog County , Yarang Village , Streams , 95°28’22.8 E, 29°29’97.0 N,19 June, 2019. ( holotype HANU ! Slide no. THTYJZL12, College of Life Science and Technology, Harbin Normal University, Harbin, China. Figs 1 & 2 are of the holotype specimen) . Isotype : Material no. YJZL12-12 , slide no. YJZL12-12 #. Cleaned material stored in Key laboratory of Algal Biology, Institute of Hydrobiology , Chinese Academy of Sciences , Wuhan, China . FIGURES 1–14 . Achnanthidium tibeticum Y.Liu & Kociolek sp. nov . LM images showing the size diminution of the valve. “=” means the raphe valve and rapheless valve are from the same frustule. Scale bar: 10 μm. FIGURES 15–20 . Achnanthidium tibeticum Y.Liu & Kociolek sp. nov . SEM pictures, external view of the raphe valve. 15. Whole valve view. 16–17. Distal raphe end from the same valve. 18. Proximal raphe ends. 19. Proximal raphe end and the areolae openings. 20. Whole valve view, showing the round areolae opening on the valve face (small arrow) and slit-like areolae on the mantle (wide arrow). Scale bars indicated in each figure. FIGURES 21–26 . Achnanthidium tibeticum Y.Liu & Kociolek sp. nov. SEM pictures, internal view of the raphe valve. 21, 26. Whole valve view. 22–23 Helictoglossa of the same valve. 24. Internal opening of the areolae. 25. Proximal raphe ends. Scale bars indicated in each figure. FIGURES 27–32 . Achnanthidium tibeticum Y.Liu & Kociolek sp. nov . SEM pictures, rapheless valve. 27–30. External view. 27. Whole valve view, showing the round areolae on the valve face (small arrow) and slit-like areolae on the mantle (wide arrow). 28–29. Apices of the same valve. 30. External areolae openings. 31–32. Internal view, apex of the valve (Fig. 31) and of the whole valve (Fig. 32). Scale bars indicated in each figure. Description:­— LM ( Figs 1–14 ): Raphe valve slightly convex, rapheless valve slightly concave. Valves linear to elliptic, with apices rounded. Length 7.9–3.6 μm, width 2.9–3.9 μm (n=25). Axial area narrow and linear. On the raphe valve, striae become coarser in the middle of valve, central area is inconspicuous. On the rapheless valves, central area is absent. On the raphe valves, striae slightly radiate in the center, becoming radiate towards the ends; 9–12 per 10 μm in center of raphe valve, denser near the ends at 18–20 per 10 μm. On the rapheless valve, striae nearly parallel in the center and become slightly radiate towards the ends; 12–15 per 10 μm. SEM: Raphe valve ( Figs 15–26 ): Externally, raphe on the valve face never extends onto the mantle, straight, distal raphe ends?-shaped, curved to the same direction ( Figs 15–17, 20 ), proximal raphe ends slightly expanded, teardrop-shaped. Striae uniseriate, areolae almost round, with varying sizes. One row of slit-like areolae present in the mantle. Internally, raphe straight, distal raphe ends terminate in small helictoglossae, proximal raphe ends curved to the opposite directions. Areolae are occluded by fine hymenate structures. Rapheless valve ( Figs 27–32 ): Externally, axial area narrow and linear; central area absent, areolae almost round. One row of slit-like areolae present on the mantle. Internally, sternum slightly raised on the apices, areolae structure similar to the raphe valve, with finely structured occlusions. Etymology:­— Named for the province of the type locality.