(Panephemeroptera Euephemeroptera Euplectoptera Anteritorna Bidentiseta Furcatergaliae  
Fimbriatotergaliae Fossoriae - Ephemera/fg9)

Nomen hierarchicum: Ephemera/fg9 [f:1810; g:1758]  (sine Ichthybotus, Behningia, Ephoron; incl. Hexagenia)

In circumscription fits:

 subfam. Ephemerinae: Koss & Edmunds 1974: 295

 Ephemera/fg9: Kluge 2000: 252

References. Kluge 2004: * * *

Autapomorphy of Ephemera/fg9.

(1) Abdominal segments VII-IX are elongate owing to elongation of their posterior portions, thus bases of tergalii VII are located at midlength or at anterior half of segment VII (Kluge 2004: Fig.70:C). This character can be used as diagnostic not only for larvae, but also for winged stages, because they have visible traces of tergalial bases. In all other Fossoriae as well as in majority of mayflies, at least tergalii II-VII are attached to posterior parts of abdominal segments.

Characters of Ephemera/fg9 of unclear phylogenetic status. 

(2) Mandibular tusk [see Fimbriatotergaliae (8)] is curved laterally-dorsally, round in section, without denticles or protuberances (Kluge 2004: Fig.70:C,E). Such structure of tusk is unique; lateral-dorsal curvation of the tusk is present also in Palingenia/f2=g1.

(3) Larval hind tibia with a prominent inner-distal angle (Kluge 2004: Fig.70:C). Non-unique apomorphy, the same in Palingenia/f2=g1.

(4) Tergalius I [see Fimbriatotergaliae (6)] is vestigial, without processes, initially bilamellate (Kluge 2004: Fig.70:C) (in Litobrancha unilamellate). The same in majority of Fossoriae (except for Behningia/fg1) and in Euthyplocia/fg1; probably, symplesiomorphy.

(5) In male imago on fore leg both claws are blunt (in subimago ephemeropteroid). Non-unique apomorphy (see Index of characters [2.2.77]).

(6) On fore wing from AA to basitornal margin several (310) veins go (Kluge 2004: Fig.71:A). Non-unique character.

Plesiomorphies of Ephemera/fg9. In larva: Maxilla with 2 dentisetae [see Bidentiseta (1)] (in Hexagenia/g1 distal dentiseta is vestigial). Unlike Cryptoprosternata, maxillary palp is normally 3-segmented (Kluge 2004: Fig.70:C); in selected specimens suture separating 2nd and 3rd segments is indistinct or lost, in this case palp is 2-segmented. Unlike Cryptoprosternata, labial palp is 3-segmented (Kluge 2004: Fig.70:C); sometimes suture between 2nd and 3rd segments is non-expressed, but in this case both segments retain shape peculiar for each of them; in 2nd segment muscle-adductor of 3rd segment can be retained or lost (particularly among individuals of Hexagenia/fg3 limbata [E.] all variants can be found from wide fan-formed muscle to its absence). Larval (and adult) patella-tibial suture is developed on middle and hind legs only.

In imago and subimago: Furcasternal protuberances are contiguous (unlike Campsurus/fg1, Caenotergaliae and some others see Index of characters [2.2.23]). In cubital field of fore wing several (36) branched or simple veins go from CuA to basitornal and tornoapical margins [see Anteritorna (1)]. Imaginal and subimaginal claws are ephemeropteroid [except for fore legs of male imago see (5)]. 1st segment of gonostylus is distinct from 2nd (unlike Behningia/fg2, Euthyplocia/fg1, Potamanthus/fg1 and some others).

Size. Fore wing length 830 mm.

Age and distribution. Palaeogene (see Ephemera/fg9 INCERTAE SEDIS) recent; Holarctic, Afrotropical, Oriental and Neotropical Regions.

The taxon Ephemera/fg9 is divided into:

1. Ephemera/fg10

1.1. plesiomorphon Sinephemera

1.2. Afromera

1.3. Ephemera/fg11

2. Hexagenia/fg1

2.1. Hexagenia/fg2

2.1.1. plesiomorphon Hexagenia/fg3 

2.1.2. Pseudeatonica

2.2. Eatonica/g1
2. 2.1. Litobrancha

2. 2.2. Eatonica/g2 

2. 2.3. Eatonigenia
Some extinct taxa have uncertain systematic position