CLADOENDESIS OF EPHEMEROPTERA

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Autapomorphies of Caenis/f3=g1.

(1) Each microtrichion on ventral side of gill operculum [see Caenoptera (3)] has a form of thin wide plate with distal margin consisting of numerous pointed spine-like processes; all microtrichia form a row parallel to margin of the operculum; usually each microtrichion is directed toward the nearest margin of the operculum. In most species the row of microtrichia is regular (Kluge 2004: Fig.88:D; Provonsha 1990: Fig.85–87); in a few species it is irregular (in tauroides [Madecocercus], rivulorum [Caenis], deani [Irpacaenis], oligosetosa [Clypeocaenis] and others). In oligosetosa [C.] each microtrichion consists of 2–3 spine-like processes only, and is directed along the operculum margin (not perpendicular to it). In some Caenis/f5=g3 instead of each microtrichion, a short row of the same microtrichia is present, which is directed perpendicular to the operculum margin (Kluge 2004: Fig.88:G).

(2) Larval protogonostyli [see Caenoptera (5)] are completely fused with abdominal sternite IX, forming an integral preanal plate, which completely lost its initial sexual dimorphism; shape of this plate is species-specific (Kluge 2004: Fig.88:E,H). When subimaginal gonostyli [non-crumpled – see Caenoptera (5)] develop under larval cuticle, they lie freely inside the preanal plate (Kluge 2004: Fig.85:B, 86:C). As larval cuticle has no special penial sheath [see Caenotergaliae (3)], larval exuviae of male and female abdominal segment IX are non-distinguishable [sexual dimorphism is present in caudalial structure only – see Caenoptera (14)]. Unique apomorphy: in all other Ephemeroptera male larval preanal plate has more or less projected external protogonostyli, thus differing from female preanal plate (only in Turbanoculata protogonostyli and preanal plate of both sexes can be lost); in Brachycercus/f1=g3 protogonostyli are retained, being extremely diminished (Kluge 2004: Fig.84:B).

Plesiomorphy of Caenis/f3=g1. unlike Brachycercus/f1=g3, labial palp is always 3-segmented.