Cymbella hubeiensis Li, 2013

Gong, Zhijun, Li, Yanling, Metzeltin, Ditmar & Lange-Bertalot, Horst, 2013, New species of Cymbella and Placoneis (Bacillariophyta) from late Pleistocene Fossil, China, Phytotaxa 150 (1), pp. 29-40 : 34

Cymbella hubeiensis Li sp. nov.

Plate 4 , Figures 20–25; holotype specimens is represented in plate 4, figure 20.

Description: Valves dorsiventral, dorsal margin strongly arched, ventral margin slightly concave except at valve-center, where it is slightly tumid. Ends not protracted, rather, broadly round. Valve length 67–77 µm; breadth 15.0– 17.1 µm, maximal length/breadth ratio about 4.2. Axial area narrow distally becoming expanded towards the middle of the valve where a central area is lacking. Raphe near or at mid-line of the valve, distinctly lateral, becoming filiform near the distal and the proximal ends or slightly reverse-lateral near the proximal ends. Striae moderately radiate throughout, becoming more radiate towards the ends, finely punctate. No isolated stigmata. Striae in the middle 6–7 in 10 µm (dorsal and ventral), becoming up to 10 in 10 µm towards the ends, puncta 16–18 in 10 µm. The ultrastructure of the external valve view shows a centrally located raphe situated in a narrow axial area (Fig. 23). Terminal fissures are deflected to the dorsal side of the valve at an angle of almost 90° (Fig. 23, 24). Apical pore fields (Figs 23, 24) are present bearing small simple poroids, not bisected by the distal raphe endings (Fig. 24). The proximal raphe endings are deflected to the dorsal side (Fig. 25). The transapical striae are composed of slit-like areolae with apically orientated foramina. There are 3–4 striae that are biseriate at the apices (Fig. 24).

Holotype: JH 91010-2, Museum of Nanjing Institute of Geography and Limnology, CAS, Nanjing, China

Type locality: Jianghan Palin , Hubei Provice. 30 o 11 ’ 18”N, 112 o 35 ’ 33”E .

Etymology: The Latin name hubeiensis refers to the location of samples.

Differential diagnosis: No similar taxa are known as yet. Cymbella hantzschiana Krammer possesses very roughly similar outlines but has conspicuously smaller size dimensions. The set of characters as valve sizes, lacking central area, low stria density, biseriate to multiseriate areolae near the ends distinguishes C. hubeiensis from all recent and fossil Cymbella taxa.

Figures

PLATE 4, Figures 20–22. Cymbella hubeiensis Li sp. nov. Light microscopy images showing the range of variation within the type population. Figure 23. External valve view in SEM, Figure 24 External view of the valve end with the dorsally bent terminal raphe end and the apical pore field. Figure 25. External view of the central area showing the proximal raphe endings. Scale bar represents 10 µm except in Figs 23–25 where scale bar = 1 µm.