Ephemeroid wing venation based upon new gigantic Carboniferous mayflies and basic morphology, phylogeny, and metamorphosis of pterygote insects (Insecta, Ephemerida)

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Abstract
Gigantic as well as very large mayflies from the middle Upper Carboniferous (Westphalian) strata of Europe and North America are described: the adult and nymph of Bojophlebia prokopi n. gen., n. sp. (Bojophlebiidae n. fam.) and the nymphs of Lithoneura piecko n. sp. and Lithoneura clayesi n. sp. (Syntonopteridae). Evolution of ephemerid wing venation during 300 million years is summarized. Autapomorphic, apomorphic, and plesiomorphic character states of venation are categorized. Venational nomenclature of Recent Ephemerida is emended based on its evolutionary changes. Evidence that wing veins occurred primitively as a pair of fluted sectors is documented in Carboniferous mayflies in the costa, subcosta, radius, anal, and jugal. Ephemeroids and odonatoids are sister groups that share the veinal anal brace AA fused with CuP at an area important for flight. Ancestral Odonatoephemerida are the sister group of the extinct haustellate Paleoptera. The Carboniferous nymphs bear three pairs of almost homonomous thoracic wings and, on the abdomen, nine pairs of legs and nine pairs of tracheal gills (wing homologues). This proves that abdominal legs have been totally reduced in Recent Ephemerida except for the claspers (gonopods) and that tracheal gills are not flattened legs. The metamorphic instar probably originated in relatively young instars. Insectan cerci developed from segmented, arched, functional legs of abdominal segment 11, which were still present in this primitive condition in Carboniferous Monura.