CLADOENDESIS OF EPHEMEROPTERA

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Autapomorphy of Hagenulus/fg1.

(1) Patella-tibial suture is lost on all legs of all stages – larva, subimago and imago (Kluge 2008: Fig.3,7).

This character is conservative in this lineage, but not unique. Among Leptophlebiidae, patella-tibial suture is lost on larval middle and hind legs, besides Hagenulus/fg1, in some other taxa, particularly in Choroterpes/g1 (including Choroterpides, Euthraulus, et al.), Thraulus/g1 and others. In these cases patella-tibial suture is lost only on larval legs, but is well-expressed on subimaginal and imaginal legs. Unlike them, in Hagenulus/fg1 patella-tibial suture is lost not only on larval, but on subimaginal and imaginal legs as well. Such loss of patella-tibial suture in all stages independently took place in some other taxa of Ephemeroptera, e.g. Nathanella (see Index of characters [1.2.18], ibid. [2.2.82]). But the assumption that American Leptophlebiidae possessing this character constitute a holophylum, does not contradict any other recently known facts.

Character of Hagenulus/fg1 of unclear phylogenetic status. 

(2) Hind wing has more or less prominent costal projection; vein Sc terminates on costal margin just distad of costal projection, far from wing apex. The same in some other taxa, some of which have possible relationship with Hagenulus/fg1 (e.g. Choroterpes/g1, Thraulus/g1), and some are evidently non-related (e.g. Terpides/g1) (see Index of character [2.2.62], [2,.2.63]).

Plesiomorphy of Hagenulus/fg1. Imaginal and subimaginal claws of all legs are ephemeropteroid (unlike pointed in Terpides/g1 and some taxa of Notogean origin – see Index of characters [2.2.85]).