Cymbopleura jianghanensis 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 : 34-35

Cymbopleura jianghanensis Li sp. nov.

Plate 4 , 5 Figures 26–39; holotype specimens is represented in plate 4, figure 36.

Description: Valves very slightly dorsiventral, elliptical-lanceolate, dorsal and ventral margins similarly arched, ends obtusely rounded and not protracted. Valve length 17.7–23.0 µm; breadth 4.2–5.7 µm, maximal length/breadth ratio about 4.4. Axial area narrow, almost on the median line of the valve. Central area broad, extending mostly on the dorsal side, versus the ventral side, where it forms a transverse rectangle with a short stria or lacking shortened striae on the ventral side. Raphe slightly ventrally displaced terminal fissures dorsally deflected. Striae slightly radiate. Striae in the middle 8–10 in 10 µm (dorsal and ventral), becoming up to 14 in 10 µm towards the ends. The ultrastructure of the external valve view shows a centrally located raphe situated in a narrow axial area (Fig. 6). Terminal fissures are deflected to the dorsal side of the valve (Fig. 7). The proximal raphe endings are deflected to the ventral side (Fig. 8). There are 3–4 biseriate striae at the ventral apices (Fig.).

Holotype: JH 91010-3, 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 jianghanensis refers to the location of samples.

Differential diagnosis: Distinguished from larger-sized species of the C. kuelbsii Krammer (2003:94) complex by the transverse rectangular central area, breadth of valve, a lacking stria in the middle of the ventral side and lower density of striae. Krammer (2003) described C. kuelbsii with a semifascia concerning the central area, 6.0– 8.5 µm in breadth, with 10–17 striae in 10 µm.

PLATE 4 , Figures 26–36: Cymbopleura jianghanensis Li sp. nov. Light microscopy images showing the range of variation within the type population.

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.

PLATE 5, Figures 37–39: External valve view of Cymbopleura jianghanensis in SEM, Figure 37. External valve view in SEM, Figure 38. External view of the central area showing the proximal dorsally bent raphe endings. Figure 39. External view of the valve end with the dorsally bent terminal raphe end. Scale bar represents 1 µm.