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).