(1) Superlingua [curved laterally – see Heptagenia/f5=g4 (1)] is especially sharply curved and stretched laterally; by its form differs from any other taxon among Heptagenia/f5=g4 (Kluge 1988: Fig.16).

(2) On tergalii I–VI costal rib is lost, and anal rib [initially situated on anal margin – see Branchitergaliae (3)] is situated at a distance from anal margin, being especially long and nearly straight (Kluge 2004: Fig.56:O). Unique apomorphy.

(3) Tergalii VII are vestigial, lack fibrillose ventral lobe, thus fibrillose lobe [see Branchitergaliae (3)] is present on tergalii I–VI only. Non-unique apomorphy (see Index of characters [1.3.59]); among Heptagenia/f5=g4 fibrillose lobe of tergalius VII is lost also in Kageronia and majority of Ecdyonurus/fg1.

(4) Glossae [initially pyramidal – see Radulapalpata (1)] with straight or slightly curved inner margin, with distal half flattened, as dorsal edge is approximated to median edge (Kluge 2004: Fig.56:I-J,N). The same in Heptagenia/f8=g7; probably, synapomorphy.

Variable characters of Stenonema/fg1. In selected species of Stenacron and Stenonema/fg3 in imago and subimago on fore tarsus 1^st segment can be shortened (like in Heptagenia/f8=g7) or not shortened.