CLADOENDESIS OF EPHEMEROPTERA

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Autapomorphies of Baetungulata.

(1) In larva, on inner side of claw instead of 2 equal rows of denticles [see Tetramerotarsata (11)] only 1, inner-anterior row is developed (Kluge & Novikova 2011: Fig.32). Larvula retains 2 equal rows of denticles (Degrange 1960: p.84 & pl.XIV: Baetis subatrebatinus, B. pumilus, B. niger, B. rhodani).

In some taxa larva has a second (inner-posterior) row of denticles, whose denticles are much shorter than denticles of the inner-anterior row [see below, Andesiops/g1 (), Heterocloeon/g1 (), ...]. Restoring of the second row in larva is possible due to retaining of this row in larvula.

In overwhelming majority of Baetungulata claw has a dense row of numerous (about 5–15) fine denticles, progressively enlarged distally; there are only a few exceptions: in a single species Takobia/g1 maxillare [Centroptilum] all denticles are lost; in some Pseudopannota/g2 there are only a few (2–4) sparse and wide denticles; in Guajirolus/g1 the last denticle is much larger than others [see below, Guajirolus/g1 ()]; (4) in Camelobaetidius/g1 claws and their denticles are modifies [see below, Camelobaetidius (1)]. 

Besides Baetungulata, a single inner-anterior row of denticles is found in some other mayfly taxa – Pentamerotarsata, Ephemerella/fg1, Leptophlebia/fg1; in these cases larvula also has 2 rows of denticles.

(2) Tergalii have lost ability to make rhythmical respiratory movements (while, as in all mayflies, tergalial muscles are retained, and tergalii are able to change pose). Non-unique apomorphy (see Index of characters [1.3.30]). Usually the whole margin of tergalius is bordered by a rib [see Tetramerotarsata (12)] (except for some specialized taxa, e.g. Baetodes/g2). Tergalius I is the smallest, in selected species completely lost.

(3) Maxillary palp is 2-segmented (the same in many other taxa). In Guajirolus/fg1 and Pseudopannota/g2 first segment of maxillary palp is divided into two parts, so palp superficially looks as 3-segmented [see below, Guajirolus/g1 (6) and Pseudopannota/g2 (6)].

(4) At least on fore leg of male subimago tarsal segments 1–4 are covered mainly by blunt microlepides. Thus, texture of subimaginal legs is the following: Femora and tibiae ere covered by microtrichiae (as in most other Ephemeroptera). On fore tarsus of male segments 1–4 are covered mainly by blunt microlepides; only in distal part of each segment pointed microlepides can be present (unlike some other Tetramerotarsata, whose fore tarsus of male is entirely covered by pointed microlepides). Distal segment of fore tarsus of male and tarsi of other legs are covered either by pointed, or by blunt microlepides [see below, Baetofemorata (2)].