Pseudostaurosira sajamaensis E. Morales & Ector in Morales et al. 2012b, Fottea 12, p. 45, figs 12-26, 45-56.

Morales, Eduardo A., Wetzel, Carlos E. & Ector, Luc, 2021, New and poorly known " araphid " diatom species (Bacillariophyta) from regions near Lake Titicaca, South America and a discussion on the continued use of morphological characters in " araphid " diatom taxonomy, PhytoKeys 187, pp. 23-70 : 23

Pseudostaurosira sajamaensis E. Morales & Ector in Morales et al. 2012b, Fottea 12, p. 45, figs 12-26, 45-56.

Figs 1M-S (LM); 2E, F (SEM)

Comment.

This taxon was first described from the Desaguadero River; here we also report its finding in the Sajama River. The population found in the latter falls well within the features described by Morales et al. (2012b) based on the Desaguadero River sample.

At the LM level, the narrowly elliptical valves with pointy ends and coarser striation can be used to recognize the taxon in a first instance. At the SEM level, the transapically elongated and wide areolae (Fig. 2F ) are present in the majority of specimens from both sites reported here and the valve face typically and gradually transitions into the mantle, making the striae on the mantle partially visible in top outer views (Fig. 2E , and also see LM images in Figs 1M-S ). The areolae vary in shape from round to trapezoid on the valve face and there is usually one very large trapezoid areola on the mantle. The volae are conspicuous and form an entangled structure. The spines have a flattened body, but they look sagittate in lateral view due to the presence of well-developed stipules. These spines sometimes have a V-shaped cleft on its back, and the tips terminate in a single or two ends (diapason-shaped) that have serrate borders pointing downward. The stipules are well-developed giving the spines a profile resembling an arrow (sagittate).

As was the case with the Desaguadero population, the Sajama River specimens lack or have weakly developed apical pore fields. Regarding the girdle elements, the valvocopula is conspicuously wider than the rest of the elements and all are open (Fig. 2F ).

No changes in valve diagnostic measurements were yielded by our observations of Sajama River material.

Figures

Figure 1. A-M ' LM images of little known and new " araphid " diatoms from the Bolivian Altiplano A-E Nanofrustulum cataractarum F-L N. rarissimum M-S Pseudostaurosira sajamaensis T-Z P. pulchra sp. nov. (Fig. 1 U is the holotype) A' - G ' P. aedes sp. nov. (Fig. 1 A ' is the holotype). H' - M ' P. heteropolaris sp. nov. (Fig. 1 I ' is the holotype). Scale bar: 10 µm.

Figure 2. A-F SEM images of little known " araphid " diatoms from the Bolivian Altiplano A, B Nanofrustulum cataractarum A specimen from the Desaguadero River, showing quasifract girdle elements with prominent ligulae (white arrows) B specimen from the Sajama River showing common internal depression into which the areolae open (dotted arrows) and the blister-like depositions of silica at the abvalvar edge of the mantle C, D N. rarissimum from the Desaguadero River C small, spineless valve D internal view showing apical and foot pole pore fields (black arrows) and internal depressions containing all areolae within a stria (dotted arrow) E, F Pseudostaurosira sajamaensis from the Desaguadero River E top view showing gradual transition of valve face to mantle and the reduced apical pore fields (black arrow) F side view of two half cells still attached by heavily silicified spines. Notice open girdle elements (white arrows). Scale bars: 1 µm (B); 3 µm (C, E); 4 µm (A, D); 5 µm (F).