The diatom genus Ulnaria (Bacillariophyta) in China Author Liu, Bing https://orcid.org/0000-0002-8516-325X College of Biology and Environmental Sciences, Jishou University, Jishou 416000, China jsulb@outlook.com text PhytoKeys 2023 2023-06-23 228 1 118 http://dx.doi.org/10.3897/phytokeys.228.101080 journal article http://dx.doi.org/10.3897/phytokeys.228.101080 1314-2003-228-1 576A4D0BFA9A5B62B60571F9F54D9E9F Ulnaria xieriverensis Bing Liu sp. nov. Figs 73 , 74 , 75 , 76 Holotype. Slide JIUDIA202313, specimen circled on slide, illustrated as Fig. 73A . Registration. PhycoBank http://phycobank.org/103819. Type locality. China. Hunan province: Huping Mountain National Nature Reserve, Xie River, a sampling location ( 30°1'9"N , 110°37'46"E , 400 m a.s.l.), collected by Bing Liu, March 14, 2021. Description. LM (Figs 73 ). Valves generally linear (i.e., valve margins almost parallel), slightly undulate in larger specimens (Fig. 73A-C , see also Fig. 76B, C ), parallel in smaller specimens (Fig. 73D-H , see also Figs 74A , 75A , 76A ). Valve tapers towards apex, then it is protracted to broadly rostrate poles. Valve dimensions (n = 33): length 64-120 μm , width 6.0-8.6 μm at centre. Sternum distinct, extending length of valve. Central area completely absent. Striae parallel, radiate only approaching each pole, and mostly opposite one another across sternum. Stria density 10.5-12 (often 11) in 10 μm . Figure 73. Ulnaria xieriverensis sp. nov., x 1000, LM A-H eight valves exhibiting a size diminution series, note the almost parallel but slightly undulate valve margins in larger specimens ( A-C ) and parallel valve margins in smaller specimens ( D-H ). A Micrograph of holotype specimen. Scale bar: 10 μm . SEM (Figs 69 - 72 ). Valve characterized by relatively wide virgae, interconnected with vimines, closing plates affixed with a few struts to the areolar wall (Fig. 74B-D ). Ocellulimbus composed of ca. 16 pervalvar and 9 transverse rows of porelli. Two horn-like projections protruding over the ocellulimbus (Fig. 74E, F , two arrows, respectively). Striae uniseriate. Stria situated opposite each other across sternum, equidistant until radiate at poles, areolae become elongated closer to the mantle (Fig. 75B-F ). One rimoportula present at each pole, externally expressed as a simple hole (Fig. 74C-F ), internally bilabiate, situated close to sternum (Fig. 75C, E, F ), sometimes displaced, against mantle (Fig. 75D ). Central area completely lacking (Figs 74A, B , 75A, B , 76A-D ). Valvocopula a closed hoop (Fig. 76A-C ). Valvocopula bearing a mostly continuous row of poroids dividing pars interior from pars exterior, located at the midline (Fig. 76D-F ), lacking ornamentation at both poles (Fig. 76E, F ). On its advalvar edge, valvocopula has a row of serrated projections, each corresponding internally to a virga (Fig. 76D, E , three arrows, respectively). Figure 74. Ulnaria xieriverensis sp. nov., external view, SEM A a complete valve B middle part detail from A , note central area is completely absent C, D two apical details from A . E, F Two other apical details, note two horn-like projections protruding over the ocellulimbus (two arrows respectively). Scale bars: 10 μm ( A ); 1 μm ( B-F ). Figure 75. Ulnaria xieriverensis sp. nov., internal view, SEM A a complete valve B middle part detail from A , note central area is completely absent C, D two apical details from A , note one rimoportula located against the mantle ( D , arrow) E, F two other apical details. Scale bars: 10 μm ( A ); 1 μm ( B-F ). Figure 76. Ulnaria xieriverensis sp. nov., internal view, SEM A a complete valve with valvocopula B, C two complete valves with valvocopula, note undulate valve margins D middle detail from A , note the central area is completely absent and a row of serrated projections over virgae (three arrows) E, F two apical details from A , note serrated projections over virgae ( E , three arrows). Scale bars: 10 μm ( A-C ); 1 μm ( D-F ). Etymology. Named after Xie River, where the species was found. Ecology and distribution. Epilithic in a mountain stream with oligotrophic waters. Ulnaria hupingensis was found in the same sampling site with U. xieriverensis and the environmental parameters see above. So far, its distribution is known only from the type locality. Discussion. Ulnaria xieriverensis is characterized by its linear valve outline, absence of central area, and rostrate apices. It differs from U. hupingensis by its linear valve outline.