Staurosira sp. 1

(Figs. 28-31)

Valves lanceolate dilated in the middle. Cuneate, subrostrate ends. Axial area narrow and lanceolate. The central area is lanceolate. Striae alternate and short, slightly radiated to the central area. Length: 11-21 μm; width: 3.9- 5.0 μm; striae 15-17 in 10 μm. The specimens observed are similar to Pseudostaurosira decipiens Morales, Chávez & Ector. Nevertheless, the P. decipiens are different from the studied population, due the lower striae density, ends rostrate in smaller individuals, and presence of a slight swelling in the region between the ends and the central area (Morales et al. 2012). The studied population is consistent with the type of material described by Metzeltin et al. (2005), except for valve length values.

Material examined: BRAZIL, MATO GROSSO DO SUL: Batayporã, Garças Lake, 21.IX.2017, sediment, D.T. Ruwer (Nupélia UEM - 18085 - 95, 18097) .

Occurrence: first citation for Upper Paraná River floodplain.