Nomen hierarchicum: Syntonoptera/fg1 [fg:1911] (incl. Lithoneura, Bojophlebia 

In circumscription fits:

superfam. Syntonopteroidea: Kukalova-Peck 1985:939.

Nominal taxa included: 

Lithoneura/g [g:1938] 

Bojophlebia/fg [fg:1985]

Anglolithoneura/g [g:2010]

References. Kukalova-Peck 1985: adult; Carpenter 1987: adult.

Characters of Syntonoptera/fg1 of unclear phylogenetic status. 

(1) Sc and RA go nearly up to wing apex; RS begins as common stem, concave, independent from RA; MA convex, MP concave, CuA convex, CuP concave. The same in Panephemeroptera, Protorrhynchota and Odonatoptera.

(2) MA begins independently from RS, but in its base is curved anteriorly and at a short distance approximated or fused with RS (unlike Euephemeroptera, where MA is basally completely fused with RS). Non-unique character.

(3) RS, MA, MP and CuA are branched, in some cases forming triads. More constant triads are peculiar for Panephemeroptera and Odonatoptera.

Size. Fore wing length presumably 100200 mm. 

Age. Late Carboniferous (USA).

Nominal species in Syntonoptera/fg1:  

carpenteri Richardson 1956 [Lithoneura]

lameerei Carpenter 1938 [Lithoneura]

mirifica Carpenter 1944 [Lithoneura]

procopi Kukalova-Peck 1985 [Bojophlebia]

schucherti Handlirsch 1911 [Syntonoptera]