Cymbella paenetruncata Li & Gong, 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 paenetruncata Li & Gong sp. nov.

Plate 2 , Figures 5–8; holotype specimens is represented in plate 1, figure 5.

Description: Valves strongly dorsiventral, dorsal margin strongly arched, ventral margin nearly straight (in small specimens) to slightly concave, except at mid-valve, where it is slightly tumid. Ends not protracted or very slightly short-protracted on the dorsal side. Valve length 70.0– 91.5 µm; breadth 21.7–24.6 µm, maximal length/breadth ratio about 4. Axial area moderately narrow, nearly linear, both branches form an obtuse angle to each other. Central area somewhat irregularly rounded or apically elliptical, about 1/4 the breadth of the valve. Raphe near or at mid-line of the valve, distinctly lateral, becoming filiform near the distal ends and slightly reverse-lateral near the proximal ends. Central pores indistinctly deflected, terminal fissures dorsally bent. Striae radiate throughout, coarsely punctate. 4–5 distinct stigmata at the ventral side of the central area, clearly separated from the middle ventral striae. Striae in the middle 7–9 in 10 µm (dorsal and ventral), becoming up to 11 in 10µm towards the ends, puncta 16–20 in 10 µm.

Holotype: JH 91010-1, 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 paenetruncata refers to the shape of the valve.

Differential diagnosis: Distinguished from the other taxa in the C. neocistula Krammer (2002:94) complex by broader valves at all cell-cycle stages, higher maximal length/breadth ratio, and very broad, almost trunctate ends. According to Krammer (2002) the breadth of valves is 12–20 µm in the middle, and he described (or depicts respectively) the end as simple and “rounded”.

Figures

PLATE 2, Figures 5–8. Cymbella paenetruncata Li & Gong sp. nov. Light microscopy images showing the range of variation within the type population. Scale bar represents 10 µm.