Ulnaria shun-biseriata sp. nov. (Bacillariophyta) from the Shun River in Hunan Province, China Author Zheng, Yan 0000-0001-7074-0678 College of Biology and Environmental Sciences, Jishou University, Jishou 416000, China Author Liu, Bing 0000-0002-8516-325X College of Biology and Environmental Sciences, Jishou University, Jishou 416000, China Author Rioual, Patrick 0000-0001-9491-9197 Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, P. O. box 9825, Beijing 100029, China & CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China Author Long, Ji-Yan 0000-0001-8160-089X School of Life Sciences, Nanjing Normal University, Nanjing 210000, China Author Zhou, Min https://orcid.org/0009-0009-2832-5417 College of Biology and Environmental Sciences, Jishou University, Jishou 416000, China text PhytoKeys 2024 2024-09-24 246 315 327 journal article 303610 10.3897/phytokeys.246.130942 11a0958f-8d26-4732-8a33-b804390aa58c Ulnaria shun-biseriata Bing Liu & Rioual sp. nov. Figs 1 , 2 , 3 , 4 Holotype . A specimen circled on the Slide DIA 2024008 , deposited in the herbarium of Jishou University ( JIU ), China, illustrated here as Fig. 1 A . Registration. Phycobank http://phycobank.org/104927 . Figure 1. Ulnaria shun-biseriata sp. nov. , LM A – I nine normal valves showing a size diminution series J – Q eight abnormal valves A illustration of holotype specimen. Scale bar: 10 μm ( I ). Type locality. China • Hunan Province : Lanshan County , Shun River , at a sampling site ( 25 ° 14 ' 55 " N , 112 ° 8 ' 32 " E , 400 m asl .), collected by Bing Liu , October 5, 2021 . Description. LM (Fig. 1 ). Valves lanceolate with slightly undulate valve margins and apiculate apices. Valve dimensions (n = 41): length 48–70 μm, width 8.3–10.7 μm at center. Sternum distinct, extending length of valve. Central area with two arrangements: an asymmetric hyaline region extending to both margins (Fig. 1 B – F ) or a hyaline area which extends to one margin with the other side bordered with a few shortened striae (Fig. 1 A, G – I ). Ghost striae sometimes present (e. g. Fig. 1 C, D ) in the central area. Striae parallel, mostly opposite one another across sternum. Stria density 8.5–11 (often 10) in 10 μm. Many abnormal valves found, all of which exhibit an asymmetry relative to the apical axis due to the valve middle part only expanding on one side, and more undulate valve margins (Fig. 1 J – Q ) than normal valves (Fig. 1 A – I ). SEM (Figs 2 – 4 ). Valves characterized by relatively wide virgae, interconnected with thin viminules, areolar closing plates having a few struts fixing them onto the areolar wall (Figs 2 – 4 ). Valves with mixed striae, mostly biseriate. Two rimoportulae per valve, one at each pole, externally expressed as simple holes (Fig. 2 E ), internally bilabiate, situated close to sternum (Fig. 4 E ). Ocellulimbus composed of pervalvar columns and transverse rows of porelli (Fig. 2 D , 3 C ). A few serrated apical outgrowths protruding over the ocellulimbus (Fig. 2 E ). Valvocopula is a closed hoop, attached to the mantle interior, surrounding internal valve margin (Fig. 4 C – F ). Each valvocopula bears a mostly continuous row of poroids dividing the pars interior from pars exterior, located at midline (Fig. 3 B – C , arrows); lacking ornamentation at either apex (Fig. 4 E, F , arrow respectively). On its advalvar edge, valvocopula bears a row of serrated projections, each corresponding internally to a virga (Fig. 4 D , two arrows). Figure 2. Ulnaria shun-biseriata sp. nov. , external view, SEM A – C three complete valves, note biseriate striae and variable central areas D, E two apical details from A , note a few serrated projections protruding over the ocellulimbus (three arrows) F details of areolae showing the closing plates. Scale bars: 10 μm ( A – C ); 1 μm ( D – F ). Figure 3. Ulnaria shun-biseriata sp. nov. , external view, SEM A valve with valvocopula B – D details from A showing the mantle, valvocopula and ocellulimbus. Scale bars: 10 μm ( A ); 1 μm ( C – D ). Figure 4. Ulnaria shun-biseriata sp. nov. , SEM , internal view A – C three valves with closed valvocopulae D middle part detail from C note central area flanked by a few marginal striae only on one side and serrated projections over each virga (two arrows) E, F two apical details from C note unornamented valvocopula at both apices (arrow respectively). Scale bars: 10 μm ( A – C ); 1 μm ( D – F ). Etymology. The specific epithet shun-biseriata is a combination of the Shun River and the adjective biseriate to reflect the type locality and the mostly biseriate character of the striae. Distribution and ecology. Known only from the type locality in which it is a common species with ca. 1 % relative abundance. The samples that included this species were scraped off the surface of stones collected in the Shun River. Hence this is a benthic, epilithic species. The associated taxa include Gyrosigma kuetzingii (Grunow) Cleve , Encyonema appalachianum Potapova , Pinnularia subgibba Krammer , P. borealis Ehrenberg , Gomphonema berggrenii Cleve , Epithemia spp. , Nitzschia spp. , Iconella spp. , among others. The following environmental parameters were measured in the field with three replications: Conductivity = 70.1 ± 0.1 μS cm - 1 ; pH = 8.5 ± 0.1; Water temperature = 24.5 ± 0.1 ° C.