CLADOENDESIS OF EPHEMEROPTERA

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(1) Larval fore legs and mouthparts are specialized as filtering (Soldan 1978: Fig.2–8; Provonsha & McCafferty 1985: Fig.1–6; 1995: Fig.3–5): Tibia and tarsus with long setae on inner and sometimes on dorsal side (non-unique apomorphy – see Index of characters [1.2.32]). Maxilla with apical field of long dense setae; canines [initially three – see Plesiomorphies of Caenotergaliae] are slender and more or less fused together; dentisetae [two – see Bidentiseta (1)] are weak and indistinguishable among setae. 3^rd segment of maxillary palp has numerous long setae [and can be fused with 2^nd segment – see Clypeocaenis/fg2 (1) below]. Labial palp has 2^nd segment shortened and 3^rd segment elongate, with numerous long setae (in Amercaenis and Clypeocaenis/g3 the 2^nd segment is several times shorter than 3^rd, only in Barnardara they are subequal).

(2) Y-shaped rib of gill operculum is modified: median rib [which stretches longitudinally from antero-median angle to posterior margin – see Caenotergaliae (1) and Caenoptera (18)] is more or less expanded in median direction; it can be slightly expanded (Kluge 2004: Fig.88:J–K), or forms a wide plate reaching median margin (Soldan 1978a: Fig.13).

(3) Plumose microtrichia on ventral side of gill operculum [see Caenis/f3=g1 (1)] are more or less reduced and directed not strictly perpendicular to margin, but obliquely (somewhat similar to Brachycercus/f1=g3); in ridens [Caenis] a regular row of multipointed microtrichia is retained, while oligosetosa [Clypeocaenis] has irregular stripe of very small, mainly bipointed microtrichia (other species have not been examined).