CLADOENDESIS OF EPHEMEROPTERA

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Autapomorphies of Rhithrocloeon/fg1.

(1) Male gonostyli [see Liberevenata (5)] are non-arched, «ankylosed» [see (1.a)]; larval protogonostyli are brought together [see (1.b)].

(1.a) Imaginal gonostyli. In contrast to all other Baetidae and most other Ephemeroptera, whose gonostyli are arched in such a manner that their apices are directed medially to meet one another, gonostyli of Rhithrocloeoninae are not arched: 1^st segments of gonostylus (immovably fused with 2^nd) is strongly projected medially-ventrally; 2^nd segment is not arched, but nearly straight or even somewhat bent in opposite direction (Kluge 2012: Fig.42). 3^rd segment of gonostylus is either diminished, or lost: it is diminished in Thraulobaetodes (Kluge 2015: Fig.36-37, 39-41) and completely lost in Rhithrocloeon/fg2 (Kluge 2012: Fig.12-18, 20, 31, 40-42, 45; Kluge 2015: Fig. 61) [see below, Rhithrocloeon/fg2 (1)] (in all other Liberevenata distal segment of gonostylus is retained).

(1.b) Larval protogonostyli. (Kluge 2012: Fig.1, 46) Male larva has protogonostyli brought together (unlike other Turbanoculata, whose protogonostyi are widely separated); in mature larva buds of subimaginal gonostyli, developed under larval cuticle, are entirely convergent, so that their apices are brought together. This character is known for Thraulobaetodes (Kluge 2015: Fig.35), three examined species of Kivuiops (Kluge 2012: Fig.1) and for Bugilliesia/g(1) sudanense [Centroptilum] (Kluge 2012: Fig.46). Unlike Rhithrocloeon/fg1, in all other Protopatellata, as well as in Anteropatellata-non-Baetovectata, buds of 2^nd segments of subimaginal gonostyli are divergent (see Index of characters [2.3.9]).

(2) Maxillary palp has 3^rd segment very small, narrower than 2^nd segment. In Rhithrocloeon/fg2 2^nd segment is widened and flattened toward apex, 3^rd segment is short and triangular, separated from 2^nd segment by oblique suture (Kluge 2012: Fig.27-28). In Thraulobaetodes 2^nd segment is not widened, 3^rd segment is very small or absent (individual variability) (Kluge 2015: Fig.5-6, Fig.8). 

Characters of Rhithrocloeon/fg1 of unclear phylogenetic status.

(3) Tergalii able to rhythmic respiratory movements (see Index of characters [1.3.30]). This was observed by me for Thraulobaetodes, Bugilliesia (griseum [Afroptilum] and udescribed species), Rhithrocloeon/fg4 (permirum [Cloeon]) and  Kivuiops/g(1) (all examined species). Structure of tergalii greatly differ [see below, Thraulobaetodes (1) and Rhithrocloeon/fg2 (4)].

(4) Hind wings, if present, of «Centroptilum-type»: narrow, with two longitudinal veins, with simple (not bipointed) hooked costal process  (Kluge 2012: Fig.43; Kluge 2015: Fig.31-32) (see Index of characters [2.2.60]). Hind wings are retained in Thraulobaetodes and plesiomorphon Bugilliesia, vestigial in Mutelocloeon, absent in Rhithrocloeon/fg3 and Adnoptilum.

(5) In subimago of both sexes, all segments of all tarsi are covered by pointed microlepides. This is true for species examined. The same in all other examined Protopatellata, and Anteropatellata-non-Baetovectata, unlike some Baetovectata, which have blunt microlepides (see Index of characters [2.2.75], [2.2.78.2], [2.2.83]).

(6) Gonovectes are completely fused with penial bridge; gonoducts open at the middle of the integral penis. In other respects penis structure is variable: in some species it retains a form of integral sclerotized bridge, movably articulated with latero-apical angles of abdominal segment IX (Kluge 2012: Fig.12-18, 31, 45; Kluge 2015: Fig.37); in some species it is partly fused with protogonostyli to form a composite construction (Kluge 2012: Fig.40-42). Complete fusion of gonovectes with penial bridge, besides Rhithrocloeon/fg1, independently occurs in Anteropatellata-Cloeon/fg1 (see Index of characters [2.3.16a]).

Plesiomorphies of Rhithrocloeon/fg1. In all stages of both sexes patella-tibial suture is present on middle and hind legs, being absent on fore leg [see Protopatellata (1)]. Fore wing with no more than one marginal intercalary in each space (Kluge 2012: Fig.21; Kluge 2015: Fig31) (unlike Baetovectata) [see Liberevenata (2)] (Index of characters [2.2.55]).