Pseudostaurosira oblonga E. Morales, C.E. Wetzel & Ector, 2021

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 oblonga E. Morales, C.E. Wetzel & Ector sp. nov.

Figs 6P-V (LM), 10A-F (SEM)

Holotype.

Slide BR-4680, Fig. 6R , Meise Botanic Garden, Belgium. Isotype. Slide DBOL-0249a, Diatomotheca Boliviensis (before HCUCB), Cochabamba, Bolivia.

Type locality.

Bolivia. Sajama Province, Department of Oruro, Sajama River, epipsammon, 17°30'33"S; 68°20'35"W, 4000 m elev., leg. G. Chávez, 05.07.2009.

Description.

Frustules rectangular in girdle view, joined together by interlocking spines. Valves oblong, isopolar, with abrupt transition from valve face to mantle and broadly rounded apices (Figs 6P-V , 10A-F ). Axial area lanceolate (Figs 6P-V ), externally and internally depressed with respect to virgae (Figs 10A-F ). Vimines short and wide (Fig. 10A-F ). Striae composed of round to elliptic areolae, decreasing in size towards the axial area (Fig. 10A, B ); wide trapezoid areolae present near the valve face/mantle transition at the base of the spine, sometimes accompanied by an additional narrower, round areola on valve mantle (Fig. 10A-F ). Striae contained in a single depression in internal view (Fig. 10C, E ). Developed volae, arising from the areolar inner periphery and projecting inwards (Fig. 10A, C, E ). Flaps little-developed on valve face, developed on valve mantle, more commonly on larger mantle areolae (Fig. 10A, F ). Spines originating from vimines at the valve face/mantle junction; solid, with elliptic base (Fig. 10F ), as wide as the vimines they sit on (Fig. 10A, B, F ); with a somewhat cylindrical body, concave sides, in the shape of a trapezium in side view (Fig. 10D, F ), and widely spatulate tip with wide lateral projections (Fig. 10F ). Stipules incipient or absent (Fig. 10A, D, F ). Apical pore fields reduced, covered by small external flaps (Fig. 10A, B, F ). Internally, apical pore field opening by means of a few very narrow, round poroids (Figs 10C ). Small blister-like depositions present on abvalvar edge of mantle, absent from apices (Fig. 10A, D, F ). Girdle elements variable in number, open, lacking pores, ligulated, with larger valvocopula (Fig. 10D, F ).

Dimensions (n> 30): Length 6.9-13.5 μm; width 3.8-4.8 μm; striae 13-14 in 10 μm.

Etymology.

The species epithet refers to the widely ellipsoidal valve outline typical of this taxon.

Distribution.

Found in the Sajama River.

Figures

Figure 6. A-V LM images of little known and new " araphid " diatoms from the Bolivian Altiplano A-D Pseudostaurosira vulpina stat. nov. E-I P. frankenae sp. nov. (Fig. 6 E is the holotype) J-O P. occulta sp. nov. (Fig. 6 K corresponds to the holotype) P-V P. oblonga sp. nov. (Fig. 6 R corresponds to the holotype). Scale bar: 10 µm.

Figure 10. A-F SEM images of Pseudostaurosira oblonga sp. nov. A, B external views showing apical pore fields covered with small flaps (black arrow in A) and other characteristics C, E internal valve features stressing on apical pore fields and striae in a depression (black arrows in C and dashed arrow in C and E respectively) D, F titled views of valves showing girdle bands (white arrow in F) and apical pore field (black arrow in F). Scale bars: 4 µm (B, C, E, F); 5 µm (A, D).