(Panephemeroptera Euephemeroptera Euplectoptera Anteritorna Bidentiseta Branchitergaliae
Heptagennota Pentamerotarsata Radulapalpata Heptagenia/f5=g4 
Ecdyonurus/fg1 - Atopopus/fg1)

Nomen hierarchicum: Atopopus/fg1 [f:2004; g:1881] (incl. Thamnodontus, Notacanthurus, Ecdyonuroides, Electrogena, Afronurus)

In circumscription fits:

 Atopopus/fg1: Kluge 2004: 181

References. Kluge 2004: * * *

Autapomorphy of Atopopus/fg1.

(1) On maxilla [which proximal dentiseta divides into two branches see Ecdyonurus/fg1 (2)] distal dentiseta divides into several branches divergent nearly from extreme base; thus the distal dentiseta looks as a bunch of stout setae (Kluge 2004: Fig.58:G-H). Unique apomorphy: in other Ecdyonurus/fg1 the distal dentiseta is integral, being either simple or bifurcate like the proximal one.

Among species examined, only a few exceptions are discovered: in Electrogena/g1 necatii [Ecdyonurus] all specimens have distal dentiseta integral, while in related species the distal dentiseta divides into branches (Belfiore, personal communication); among Ecdyonuroides/g1 sp.H4, some specimens have distal dentiseta integral, and some divided into branches. Possibly, these exceptions are results of secondary reversions.

Character of Atopopus/fg1 of unclear phylogenetic status. 

(2) Primary swimming setae [see Pentamerotarsata (6)] are lost; larval caudalii have only whorls of setae on ends of segments [see Heptagenia/f5=g4 (2)]. Non-unique character (see Index of characters [1.3.66]); among Ecdyonurus/fg1 the same in Leucrocuta/fg1.

Size. Fore wing length 715 mm.

Distribution. Old World: Palaearctic, Oriental and Afrotropical Regions.

The taxon Atopopus/fg1 is divided into:

1. plesiomorphon Thamnodontus  

2. Atopopus/fg2  

3. Notacanthurus

4. Ecdyonuroides

5. Electrogena

6. Afronurus/g1  

Some poorly known taxa have uncertaein systematic position