Eunotia pseudoambivalens Q. Liu, S. L. Xie & Kociolek

Liu, Qi, Liu, Enhui, You, Qingmin, Wang, Qinghua, Kociolek, John Patrick & Xie, Shulian, 2024, New and Interesting Diatoms from the Shiwan Wetwalls, Yunnan Province, China. III. Valve ultrastructure of four new species of Eunotia (Bacillariophyceae: Eunotiales), Phytotaxa 642 (4), pp. 242-254 : 249-250

Eunotia pseudoambivalens Q. Liu, S. L. Xie & Kociolek sp. nov. (LM: Figs 51–59, SEM: Figs 60–65)

Description: Valves arched, with the dorsal margin convex and the ventral margin concave. Ends slightly produced, rounded (Figs 51–59). Length 62–130 µm, breadth 5–7 µm. Striae straight to irregular, comprised of fine areolae. Striae number 9–14 / 10 µm. External distal raphe ends curve up onto the valve face and extend to the dorsal margin. A wide, blunt spine is present at each apex.

In the SEM, the valve exterior has striae composed of round to rectangular areolae bordered by a thin rim and occluded (Figs 60–62). The striae on the valve face are offset from their continuation onto the mantle (Fig. 62). The distal raphe ends curve next to the base of a spine and extend onto the dorsal margin. Towards each apex a short, blunt spine with a wide base is present (Fig. 61). Internally, the striae are composed of narrow slits near the center of the valve, but near the apices round, individual areolae are evident (Figs 64, 65). The raphe terminates as a helictoglossa and a rimoportula is present at one end of the valve only (to the right when the valve is oriented with the dorsal margin at the top of the image) (Fig. 64). Each apex has a pseudoseptum (Figs 63, 64).

Type: CHINA. Yunnan Province, Shiwan wet wall. Holotype Preparation Slide No. YN201904055- 1 in the Freshwater Algal Herbarium of Shanxi University ( SXU), Taiyuan, China. Isotype slide No. YN201904055-2 deposited in the Kociolek Collection at the University of Colorado ( COLO) .

Etymology: Named for its superficial resemblance to E. ambivalens Lange-Bertalot & Tagliaventi.

Comments: This species superficially resembles E. ambivalens Lange-Bertalot & Tagliaventi (in Lange-Bertalot et al. 2011) in size and general outline. The European E. ambivalens also has a reported wide variation in straie density similar to E. pseudoambivalens . The two species differ in the curvature of the external distal raphe end, presence of a terminal spine in E. pseudoambivalens (which is lacking in the European taxon) and structure of the interstriae (more robust in E. pseudoambivalens ).

Present only in sample YN201904055.