(Panephemeroptera Euephemeroptera Euplectoptera Anteritorna Bidentiseta Branchitergaliae  
Eusetisura Discoglossata Geminovenata - Oligoneuria/f4=g5)

Nomen hierarchicum: Oligoneuria/f4=g5 [f:1914; g:1843] (sine Oligoneuriella, Homoeoneuria, Elassoneuria, Fittkauneuria; incl. Lachlania, Spaniophlebia)

In circumscription fits:

 Oligoneuria/f4=g5: Kluge 2004: 145

References. Kluge 2004: * * *; Kluge 2007. 

Autapomorphies of Oligoneuria/f4=g5.

(1) Larval head shield [see Discoglossata (1)] has a pair of distinct lateral incisions by sides of eyes (Kluge 2004: Fig.51:C-D; Kluge 2007: Fig.1-3); these incisions are retained on adult head as well (Kluge 2004: Fig.50:C; Kluge 2007: Fig.13,17-18).

(2) Gonostylus with one distal segment (Kluge 2004: Fig.50:D) (instead of two initial ones). Non-unique apomorphy (see Index of characters 2.3.12]).

(3) Penis has a peculiar articulatory mechanism (Kluge 2004: Fig.50:D; Kluge 2007: Fig.23): Bases of left and right penis lobes are movably articulated one with another by a median condylus on their dorsal wall; from this condylus toward anterior-lateral angles of sternite IX, goes a pair of strong muscles. This construction allows to protract penis lobes moving them apart (Peters & Pescador 1980: Fig.26-33) and to retract penis lobes back. Unique apomorphy. 

Among Geminovenata, similar dorsal-proximal condylus occurs in Madeconeuria only, but no muscles are attached to it (Kluge 2004: Fig.48).

Variable characters of Oligoneuria/f4=g5. Among subordinate taxa of Oligoneuria/f4=g5 various combinations of following 3 characters are found (see Table below):

(4) Head can have anterior projection of unique shape. In this case larval head shield [with lateral incisions see (1)] anteriorly has a huge flat projection separated by one more pair of lateral incisions from the rest part of shield; imago has a soft frontal projection of similar shape, but much smaller and curved ventrally-posteriorly (Kluge 2004: Fig.50:C, 51:D; Kluge 2007: Fig.1-3, 13,17-18, ). This character is present in Spaniophlebia and Oligoneuria/f5=g6, but absent in Lachlania.

(5) On fore wing double vein RSa+iRS [see Geminovenata (3)] in proximal part is closely approximated to Sc+RA, thus sometimes looks as originating not from wing base, but from Sc+RA (Kluge 2004: Fig.50:A; Kluge 2007: Fig.19-22, ). This character is in this or that degree expressed in Lachlania and Oligoneuria/f5=g6, but absent in Spaniophlebia (Kluge 2004: Fig.51:A).

(6) Larval and adult cerci are contiguous by their bases; paracercus can be reduced to a small sclerite (in Lachlania) or completely lost (in Spaniophlebia sp.O3). This character is present in Lachlania and Spaniophlebia, but not Oligoneuria/f5=g6. Among other Geminovenata, paracercus can be strongly shortened (but not lost) in some species of Oligoneuriella/g2 (see Index of characters [1.3.64]).

Plesiomorphies of Oligoneuria/f4=g5. On fore wing bifurcation of MA is situated near wing base (unlike Elassoneuria/g1). In male imago on tarsus of middle and hind leg [non-functional see Geminovenata (2)] before the last (claw-bearing) segment, 3 short segments are present (if not take into account the 1st segment, which is fused with tibia, shortened and not expressed), thus tarsus looks as 4-segmented.

Size. Fore wing length 815 mm. 

Distribution. America: Neotropical and Nearctic Regions. 

The taxon Oligoneuria/f4=g5 is divided into:

1. Lachlania

2. Spaniophlebia

3. Oligoneuria/f5=g6

















1 proximal half of RSa+iRS brought together with RA

2 frontal projection

3 loss of paracercus