(Panephemeroptera Euephemeroptera Euplectoptera Anteritorna Bidentiseta Branchitergaliae
Heptagennota Pentamerotarsata Radulapalpata 
Rhithrogena/fg1 - Rhithrogena/fg2)

Nomen hierarchicum: Rhithrogena/fg2 [f:1917; g:1881] (sine Paegniodes, Epeorus; incl. Cinygmula)

In circumscription fits:

 Rhithrogena/fg2: Kluge 2004: 191

References. Kluge 1993: *; 2004: * * *

Autapomorphies of Rhithrogena/fg2.

(1) Maxilla [see Radulapalpata (3)] is shortened (length of median margin is subequal to maxilla width), widened apically, median margin is inclined forming acute angle with apical margin; ventral row of setae [see Branchitergaliae (1)] in its distal part is curved laterally and diverges from median margin, being perpendicular to apical margin (Kluge 2004: Fig.62:A).

In other Radulapalpata maxilla has different shape (see Index of characters [1.1.29] and [1.1.30]); only in Epeorus/fg3 median margin is inclined as strongly as in Rhithrogena/fg2, but there the ventral row of setae is straight and parallel to the median margin all over its length (Kluge 2004: Fig.64:L).

(2) Ventral side of 2nd+3rd segment of maxillary palp bears a longitudinal arched pigmented stripe, which borders the field of scraping setae [see Rhithrogena/fg1 (1)] and reaches the extreme pointed apex of the palp (Kluge 2004: Fig.62:A,D) (on dorsal side, as in other Radulapalpata, a vestige of transverse suture between 2nd and 3rd segments is retained). In other Rhithrogena/fg1 such stripe is absent, or indistinct, or not reaching apex of palp.

(3) Larva has a peculiar pose of swimming: legs are folded and pressed to lateral margins of body (Kluge 2004: Fig.9:C); they are not turned ventrally (unlike many Heptagenia/f6=g5) and do not move when larva swims (unlike Epeorus/fg3 and some others) [see Heptagennota (1)]. Larvae inhabit rapid streams [see Autapomorphies of Rhithrogena/fg1], where it normally does not swim; swimming movements can be observed if put larva into stagnant water.

(4) Penis has a pair of ventral titillators immobile spines situated on ventral side of penis; in Cinygmula these ventral titillators are present besides median titillators [see Pentamerotarsata (5)], in Rhithrogena/fg3 only ventral titillators are present. In selected species of Cinygmula and Rhithrogena/fg3 ventral titillators are lost.

Characters of Rhithrogena/fg2 of unclear phylogenetic status. 

(5) Superlinguae are widest in middle part and convergent toward apex. The same in Epeorus/fg3, but unlike other Radulapalpata, whose superlinguae are divergent; probably, plesiomorphy within Rhithrogena/fg1 [for comment see Ironodes (3) below].

(6) Subimaginal lateroparapsidal stripe of pigmented area of mesonotum in its posterior part is curved laterally, repeating curvation of lateroparapsidal suture [see Rhithrogena/fg1 (3)], thus it does not touch medioparapsidal suture (Kluge 2004: Fig.63:A,C). The same in Epeorus/fg1; possibly synapomorphy (unlike Paegniodes).

Plesiomorphies of Rhithrogena/fg2. Glossae are pyramidal [see Radulapalpata (1)] (Kluge 2004: Fig.62:E,G). Unlike Epeorus/fg1: larval paracercus is subequal to cerci [see Pentamerotarsata (6)]; imaginal and subimaginal mesonotal suture is normally developed [see Plesiomorphies of Branchitergaliae] (Kluge 2004: Fig.63).

Size. Fore wing length 517 mm.

Distribution. Holarctic and Oriental Region.

The taxon Rhithrogena/fg2 is divided into:

1. Cinygmula/g1

2. Rhithrogena/fg3
2.1. Rhithrogena/fg4

2.2. Epeiron/g1

2.3. Himalogena

2.4. Sibirigena