SEM images of the trophi. A–F Ramus (“unci”) teeth (ventral sides of the trophi directed upwards) A teeth absent (S. pectinata) B no distinct teeth, only a serrated plate (S. vorax) C teeth distinctly incised (S. gyrina) D teeth distinctly incised and separated into two groups by a deep sulcus (arrow; S. oblonga) E dorsal group of teeth distinctly incised and ventral group of teeth comb-like (S. triophthalma) F dorsal teeth comb-like and ventral teeth distinctly incised, groups of teeth separated by a deep sulcus (arrow; S. baltica) G–J Shape of the lateral fulcrum (normal and dashed arrows) and thickness of the cauda (arrow-heads) (trophi from lateral view, ventral sides directed upwards) G fulcrum blade-like, narrow, distal end not oblique, cauda of medium thickness (S. tremula) H fulcrum machete-like, distal end oblique, cauda of medium thickness (S. oblonga) I fulcrum broad, with distinct dorsal thickening (dashed arrow) and ventral lamella (arrow; S. vorax) J fulcrum axe-shaped, very broad, with oblique distal end, cauda robust (S. longipes) K, L Shape of the hypopharynx (arrow) K small to medium, robust (S. tremula) L broad to very broad, laterally pointed / dagger-like (S. stylata). Scale bar: 20 µm.