Cymbella shii 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 : 32

Cymbella shii Li sp. nov.

Plate 3 , Figures 9–13; holotype specimens is represented in plate 3, figure 9.

Description: Valves dorsiventral, rhomboid-lanceolate, dorsal margin strongly convex, ventral margin nearly straight (in small specimens) to slightly concave, except at the mid-valve, where it is slightly tumid. Ends not protacted and more or less obtusely rounded. Valve length 46–88 µm; breadth 15–18 µm, maximal length/ breadth ratio about 4.9. Axial area moderately wide, lanceolate, broadening gradually towards the valve center, about 1/4 to 1/3 the breadth of the valve at center. Central area is absent or a little wider than axial area. Raphe slightly ventrally displaced, slightly lateral, central raphe ends very slightly deflected to the ventral side and terminal fissure (Fig. 10) curved to the dorsal side. Striae moderately radiate, becoming more strongly radiate towards the ends, finely punctate. No isolated stigmata. Striae in the middle 8–9 in 10µm (dorsal and ventral), becoming up to 12 in 10 µm towards the ends, puncta 15–19 in 10µm.

Holotype: JH 91010-4, 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 shii refers to the collector of the samples, Dr. Shi.

Differential diagnosis: Distinguished from all species of the C. hantzschiana Krammer (2002:47) complex by the valve outline, higher size dimensions, slightly lower maximal length/breadth ratio, slightly lower density of striae, and the wider axial area (see Krammer 2002). The valve shape of C. hantzschiana is semilanceolate, length 25–59 µm, breadth 8–12 µm, ratio 5.5, striae 8–11 in 10 µm and the axial area is narrow, linear.

Figures

PLATE 3, Figures 9–13: Cymbella shii Li sp. nov. Light microscopy images showing the range of variation within the type population. Scale bar represents 10 µm.