Pseudostaurosira frankenae E. Morales, C.E. Wetzel & Ector sp. nov.

Figs 6E-I (LM), 8A-F (SEM)

Holotype.

Slide ANSP GC 26815, Fig. 6E, Diatom Herbarium, Academy of Natural Sciences, Philadelphia (ANSP). Isotype. Slide DBOL-0246a, Diatomotheca Boliviensis (before HCUCB), Cochabamba, Bolivia.

Type locality.

Bolivia. Sajama Province, Department of Oruro, Desaguadero River, epipsammon, 17°23'51"S; 68°14'33"W, 3701 m elev., leg. G. Chávez, 05.07.2009.

Description.

Frustules rectangular with a curved middle portion in girdle view, joined together by interlocking spines. Valves cruciform, isopolar, with abrupt transition from valve face to mantle. Broadly rounded valve ends (Fig. 6E-I). Axial area lanceolate with a broad central inflation (Fig. 6E-I), externally and internally depressed with respect to virgae (Fig. 8A-C). Vimines short and wide (Fig. 8A, B, E, F). Striae typically composed round to elliptic areolae, decreasing in size towards the axial area (Fig. 8A, B); a single elliptical areola present on valve mantle (Fig. 8A-C, E, F). Well-developed volae, arising from the areolar inner periphery and projecting inwards (not shown here). Internally, depositions on volae forming round to elliptic structures, sealing areolae (Fig. 8C, D). Flaps persistent, a single disk-like one covering each areola in external view (Fig. 8A, B, E, F), 1-3 in enlarged mantle areolae (Fig. 8C). Spines originating from vimines at the valve face/mantle junction; solid, with round to elliptical base (Fig. 8E), wider that the vimines they sit on (Fig. 8F); flattened, with shallow biconcave sides, triangular in side view (Fig. 8A, B, E, F), and with spatulate body, bifurcate at the top (Fig. 8C). Stipules absent. Apical pore fields of cavernous appearance in external view, occluded by heavy silica deposition to the point only one row of pores can be seen (Fig. 8A, B, E, F). Internally, apical pore field opening into roundish depression, revealing several rows of round poroids (Fig. 8C, D). Well-developed blister-like depositions present on abvalvar edge of mantle also covering both apices (Fig. 8A-C, D-F). Girdle elements variable in number, open, lacking pores, ligulated, with larger valvocopula (Fig. 8A, B, F).

Dimensions (n> 30): Length 8.7-12.0 μm; width 6.7-7.7 μm; striae 14 in 10 μm .

Etymology.

The species is dedicated to the late Dr. Margot Franken, Professor and Researcher from the Ecology Institute, University Mayor de San Andrés, La Paz, Bolivia. Dr. Franken, originally from Germany, worked in Bolivia from 1985 to 2021, focusing on bioindication, urban ecology, water management and ecological architecture.

Distribution.

Found only in the Desaguadero River.