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 neobiceps Bing Liu sp. nov. Figs 48 , 49 , 50 , 51 , 52 , 53 Holotype. Slide JIUDIA202308, specimen circled on slide, illustrated as Fig. 48A . Registration. PhycoBank http://phycobank.org/103814. Type locality. China. Qinghai province: Menyuan County, an unnamed river, at a sampling location named Kengtan ( 37°27'28"N , 101°23'15"E , 2940 m a.s.l.), collected by Bing Liu, July 18, 2019. Description. LM (Fig. 48 ). Valves linear-lanceolate with distinct capitate apices (Fig. 48A-K , see also Figs 49A , 50A ). Valve dimensions (n = 23): length 202-307 μm , width 4.5-6.7 μm at centre. Sternum distinct, extending length of valve. Central area very variable: hyaline region extending to both margins (e.g., Fig. 48F, K ), can be circumscribed by both short marginal striae and isolated areolae (e.g., Fig. 48B, C, G, J ), nearly absent (Fig. 48H ) or completely lacking (Fig. 48A, D, E, I ). Striae parallel, radiate only approaching each pole, 9-11 in 10 μm , increasing near each pole. Striae on both sides of sternum, some opposite each other, and others alternate. Figure 48. Ulnaria neobiceps sp. nov., x 400, LM A-K eleven valves exhibiting a size diminution series, note the linear-lanceolate valve outline and variable central areas A micrograph of holotype specimen. Scale bar: 20 μm . Figure 49. Ulnaria neobiceps sp. nov., external view, SEM A a complete valve B middle part detail from A , note central area complete absent C-F apical details from A , note the capitate apices. Scale bars: 20 μm ( A ); 2 μm ( B ); 3 μm ( C-E ); 1 μm ( F ). Figure 50. Ulnaria neobiceps sp. nov., internal view, SEM A a complete valve B middle part detail from A , note the very small central area (arrow) C, E two poles from A , note that valve margins do not constrict near the capitate apices (two arrows, respectively) D, F two apical details, note the capitate apices and apical pore field. Scale bars: 20 μm ( A ); 2 μm ( B-F ). SEM (Figs 49 - 53 ). Valve characterized by a series of relatively wide virgae and interconnected with vimines (Fig. 49B-F ). Central area completely lacking (Fig. 49B ), hyaline area circumscribed by both short marginal striae and isolated areolae (Figs 50B , 51A, C, D ), or hyaline area extending to both margins (Fig. 51B ). Striae uniseriate, on both sides of sternum, opposite or alternate, areolae gradually become elongated from sternum to mantle (Figs 50B-F , 51A-D ). Ocellulimbus composed of ca. 24 pervalvar and 8 transverse rows of porelli. Two horn-like projections protruding over the ocellulimbus (Fig. 52D , two arrows). One rimoportula located at each pole, externally expressed as a simple hole (Fig. 49F ), internally bilabiate, situated close to sternum at an angle (Fig. 50D, F ). Valvocopula closed, surrounding the valve internal margin (Fig. 52A ), bearing a mostly continuous midline row of poroids dividing pars interior from pars exterior (Figs 52B-F , 53A-F ), lacking ornamentation at both poles (Figs 52D, F , 52C-F ). On its advalvar edge, valvocopula has a row of serrated projections, each corresponding internally to a virga (Fig. 52B, C, E ). Shelf-like projections present at pars interior of each apex (Fig. 53C-F , two arrows, respectively). Figure 51. Ulnaria neobiceps sp. nov., internal view, SEM A-D four middle valve parts showing very variable central areas. Scale bars: 2 μm ( A-D ). Figure 52. Ulnaria neobiceps sp. nov., internal view, SEM A a valve with valvocopula B-F details from A , showing the valvocopula structure, note two horn-like projections protruding over ocellulimbus. Scale bars: 20 μm ( A ); 3 μm ( B, C, E ); 2 μm ( D, F ). Figure 53. Ulnaria neobiceps sp. nov., valvocopula, SEM A a complete valvocopula B-D details from A , showing row of poroids interrupted in the middle and shelf-like projection at each apex ( C , D , two arrows respectively) E, F other two apical details of valvocopula have the same apical structure. Scale bars: 20 μm ( A ); 3 μm ( B ); 2 μm ( C-F ). Etymology. The epithet biceps has been occupied by Ulnaria biceps ( Kuetzing ) Compere , so here the epithet neobiceps is used, which is a combination of neo (new) and biceps (two capitate) reflecting its two distinctly capitate poles. Ecology and distribution. Ulnaria neobiceps , U. blancoi , and U. menyuanensis were commonly found in the same sampling site of Kengtan. Thus, U. neobiceps lives on the stone surfaces of a plateau river. So far, its distribution is known only from the type locality. Discussion. Ulnaria neobiceps is characterized by its linear-lanceolate valve outline, variable central area, distinctly capitate apices, and long and slender valve. Both U. neobiceps and U. capitata (Ehrenberg) Compere have capitate apices, but the apices of U. capitata are rhomboid-capitate (see Morales et al. 2007 , p. 49, figs 13-17; p. 51, figs 18-20, as Synedra capitata ) whereas the apices of U. neobiceps are rounded-capitate. Moreover, U. neobiceps has very variable central area while U. capitata lacks central area.