CLADOENDESIS OF EPHEMEROPTERA

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(1) Imaginal and subimaginal mesonotal suture is completely lost (Kluge 2004: Fig.64:D). Loss of mesonotal suture takes place also in some other Ephemeroptera, thus from a formal point of view, this apomorphy is not unique. But in Epeorus/fg1 mesonotal suture had disappeared by a peculiar way: not by gradual curvation (characteristic for Tetramerotarsata, Fimbriatotergaliae and Leptophlebia/fg1) or by gradual smoothing out (as in some Tricorythus/fg1) but by a saltation. In all other Radulapalpata mesonotal suture is distinct and has uniform shape (transverse in median part and turned posteriorly in places where it connects with medioparapsidal sutures).

(2) Larval paracercus is reduced to a 1-segmented vestige; primary swimming setae of cerci are completely lost [see Pentamerotarsata (6)]. The same in some other rheophilous mayflies (see Index of characters [1.3.64]).

(3) On fore wing [see Heptagennota (5) and Plesiomorphies of Radulapalpata] veins AA and AP proximally have a common stem (Kluge 1993: Fig.32). In other mayflies they originate independently or are connected only at extreme base.

(4) In male imago 1^st segment of fore tarsus is always long, approximately equal to 2^nd segment (unlike most other Pentamerotarsata, where it is usually equal to 1/6–7/8 of 2^nd segment).

(5) On maxilla pectinate setae of apical-ventral row [see Radulapalpata (3)] are vestigial (in Bleptus and Ironodes) or lost (in Epeorus/fg3). Non-unique apomorphy: incomplete or complete reduction of these setae takes place also in Cinygma, Raptoheptagenia and some representatives of Heptagenia/f7=g6.

(6) On maxilla ventral row of setae [see Branchitergaliae (1)] is always straight, not curved laterally (Kluge 2004: Fig.64:E,H,L; 65:F). The same in Cinygma and Paegniodes (see Index of characters [1.1.30]); possibly symplesiomorphy.

Shape of maxilla is variable, in Epeorus/fg3 being sharply different from that of Bleptus and Ironodes [see Epeorus/fg3 (1) below].

(7) Subimaginal lateroparapsidal stripe of pigmented area of mesonotum in its posterior part is curved laterally, repeating curvation of lateroparapsidal suture [see Rhithrogena/fg1 (3)], does not touch medioparapsidal suture (Kluge 2004: Fig.64:D). The same in Rhithrogena/fg2; possibly synapomorphy (unlike Paegniodes).

(8) Patella-tibial suture (initially present on middle and hind legs) is lost on all legs of larva, being retained on middle and hind legs of subimago and imago (only in Bleptus it is lost in subimago and imago also). Non-unique apomorphy (see Index of characters [1.2.18]). Among Epeorus/fg1 only in Belovius/g2 larva has developed patella-tibial suture on middle and hind legs; probably, in this case the suture is restored secondarily; this is possible, because the suture was retained in adult stages.

Variable characters of Epeorus/fg1. In selected species larval abdominal terga have unpaired median or paired submedian projections or spines directed posteriorly; particularly, unpaired spines are present in Bleptus and selected species of Iron/g1, paired spines – in Ironodes and selected species of Iron/g1 and Epeorus/fg4; some species have spines paired on anterior segments and unpaired on posterior segments (non-unique character – see Index of characters [1.3.3]).