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 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. Chavez , 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 ). Figure 3. A-F SEM micrographs of Pseudostaurosira pulchra sp. nov. from the Bolivian Altiplano A, B outer views of valves showing axial area, striae and spines features C inner view of valve still attached to neighboring cell. Black arrow indicates absence of apical pore field. Dotted arrow points to depression into which the stria opens internally D tilted view of frustule. Notice larger valvocopula, lateral growth of spines and blister-like depositions on abvalvar edge of mantle E outer view of valve tip. Black arrow denotes absence of apical pore field. Notice round to elliptical spine base and larger areola on valve mantle. F frustule attached to neighboring valve by means of heavily silicified spines. Notice open girdle elements (white arrow) and depositions along abvalvar mantle edge. Scale bars: 2 µm ( E ); 4 µm ( C, F ); 5 µm ( A, B, D ). 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.