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 Author Morales, Eduardo A. https://orcid.org/0000-0001-5998-4831 Water Laboratory, University of Evora, P. I. T. E. Rua da Barba Rala No. 1, 7005 - 345 Evora, Portugal & Institute of Earth Sciences - ICT, University of Evora, Rua Romao Ramalho n °. 59, 7000 - 671 Evora, Portugal edu_mora123@outlook.com Author Wetzel, Carlos E. https://orcid.org/0000-0001-5330-0494 Observatory for Climate, Environment and Biodiversity (OCEB), Environmental Research and Innovation (ERIN) Department, Luxembourg Institute of Science and Technology (LIST), 41 rue du Brill, 4422 Belvaux, Luxembourg Author Ector, Luc Observatory for Climate, Environment and Biodiversity (OCEB), Environmental Research and Innovation (ERIN) Department, Luxembourg Institute of Science and Technology (LIST), 41 rue du Brill, 4422 Belvaux, Luxembourg text PhytoKeys 2021 2021-12-13 187 23 70 http://dx.doi.org/10.3897/phytokeys.187.73338 journal article http://dx.doi.org/10.3897/phytokeys.187.73338 1314-2003-187-23 6AF5EAA0500558E5838FD916171188B8 Pseudostaurosira heteropolaris E. Morales, C.E. Wetzel & Ector sp. nov. Figs 1H '-M' (LM), 5A-F (SEM) Holotype. Slide ANSP GC 26815, Fig. 1I ', 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. Chavez , 05.07.2009. Description. Frustules rectangular in girdle view (Fig. 5C, D ), joined together by interlocking spines (Fig. 5C ). Valves ovoid to elliptic, heteropolar, with gradual transition from valve face to mantle (Figs 1H '-M' , 5A-F). Axial area elliptic (Figs 1H '-M' , 5A, B, F), externally slightly depressed with respect to virgae, internally at the same level as virgae (Fig. 5A, D, E ). Virgae much wider than striae (Fig. 5A, D-F ). Vimines shorter than virgae and wide (Fig. 5A, B, D-F ). Striae composed of narrow, apically elongated, rectangular to semi-elliptic areolae (Fig. 5A-F ). Areolae diminish in size from valve face/mantle junction towards striae extremes at about the same rate (Fig. 5F ). Volae arising from up to two points (typically one) within the areolar inner periphery, projecting inwards (Fig. 5A, B, D-F ). Base of volae thick and giving areolae a C-shape (Fig. 5A, B ). Flaps absent. Spines originating from vimines at the valve face/mantle junction, solid, with elliptic to rectangular base, wider than the vimines they sit on; cylindrical body with biconcave sides, spatulate tips with pinnatifid (with deep lateral) bifurcations (Fig. 5C, D ). Stipules absent (Fig. 5D ). Apical pore fields very reduced with no more than 3 cavernous poroids in external view; not seen in internal view (Fig. 5F ). Small blister-like depositions present on abvalvar edge of mantle, including at the valve apices (Fig. 5C-F ). Girdle elements variable in number, open, lacking pores, ligulated, with larger valvocopula (Fig. 5C, E, F ). Figure 5. A-F SEM images of Pseudostaurosira heteropolaris sp. nov. from the Bolivian Altiplano A, B Valve views showing striation pattern and features of the axial area, virgae, vimines, and spine location C side view of complete frustule and neighboring cell showing girdle bands (white arrows denote open copulae). White arrows point to open girdle elements D close up of C showing details of spines with bifurcations with pinnatifid projections, characteristics of the striae on valve mantle and the features of the blisters E broken frustule with girdle bands. Pattern of volae within areolae is also shown F frustule in side, tilted view. Notice open copulae (white arrow) and reduced apical pore field with cavernous poroids (black arrow). Scale bars: 1 µm ( D ); 3 µm ( A-C, E ); 4 µm ( F ). Dimensions (n> 50): Length 3.0-4.3 μm ; width 2.6-3.3 μm ; striae 13-16 in 10 μm . Etymology. The epithet of this species refers to its typical heteropolar valve outline. Distribution. Found in the Desaguadero River.