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

Figs 1T-Z (LM), 3A-F (SEM)

Holotype.

Slide ANSP GC 26815, Fig. 1U. 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 in girdle view (Fig. 3D), joined together by interlocking spines (Figs 3C, F). Valves narrowly lanceolate, isopolar, with abrupt transition from valve face to mantle. Rostrate valve ends in larger specimens, broadly rounded in smaller ones (Figs 1T-Z). Axial area narrowly lanceolate (Figs 1T-Z, 3A, B) and externally and internally depressed with respect to virgae (Fig. 3A, B). Internally, striae open in small trapezoid, transapically elongated depressions (Fig. 3C). Vimines short and wide, restricted to the valve face/mantle junction; additional ones rarely present on either valve face or valve mantle (Fig. 3C). Striae typically composed by two narrow, round to elliptic areolae, one on valve face and a larger one on the valve mantle (Figs 3E, F). Well-developed volae, arising from the areolar inner periphery and projecting inwards forming a loose mesh-like structure (Figs 3C, E). Flaps usually present in various stages of development, typically single and disk-like on valve face and two or more on mantle areolae (Fig. 3A). Spines originating from vimines at the valve face/mantle junction; solid, with round to elliptical base, wider that the vimines they sit on; flattened, with biconcave sides and spatulate body, truncated (cut) at the top or with a short bifurcation (Fig. 3A, B, D, E, F). Stipules absent. Apical pore fields absent (Fig. 3C, E). Well-developed blister-like depositions present on abvalvar edge of mantle also covering both apices (Fig. 3D-F). Girdle elements variable in number, open, lacking pores, ligulated, with larger valvocopula (Fig. 3D, F).

Dimensions (n> 50): Length 5-22 μm; width 2.4-3.0 μm; striae 13-16 in 10 μm .

Etymology.

The epithet makes reference to the neat and eye-catching morphology of the frustules.

Distribution.

Found in the Desaguadero and Sajama rivers.