Being implied in flight, mimetism, communication, and protection, the insect wings were crucial organs for the mega diversification of this clade. Despite several attempts, the problem of wing evolution remains unresolved because the basal parts of the veins essential for vein identification are hidden in the basivenal sclerites. The homologies between wing characters thus cannot be accurately verified, while they are of primary importance to solve long-standing problems, such as the monophyly of the Palaeoptera, viz. Odonatoptera, Panephemeroptera, and Palaeozoic Palaeodictyopterida mainly known by their wings. Hitherto the tools to homologize venation were suffering several cases of exceptions, rendering them unreliable. Here we reconstruct the odonatopteran venation using fossils and a new 3D imaging tool, resulting congruent with the concept of Riek and Kukalová-Peck, with important novelties, viz. median anterior vein fused to radius and radius posterior nearly as convex as radius anterior (putative synapomorphies of Odonatoptera); subcostal anterior (ScA) fused to costal vein and most basal primary antenodal crossvein being a modified posterior branch of ScA (putative synapomorphies of Palaeoptera). These findings may reveal critical for future analyses of the relationships between fossil and extant Palaeoptera, helping to solve the evolutionary history of the insects as a whole.

Department of Zoology Charles University Viničná 7 CZ 128 43 Praha 2 Czech Republic

Institut de Systématique Évolution Biodiversité ISYEB UMR 7205 CNRS MNHN UPMC EPHE Muséum national d'Histoire naturelle Sorbonne Universités 57 rue Cuvier CP 50 Entomologie F 75005 Paris France

State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences 39 East Beijing Road Nanjing 210008 China

Université de Poitiers UFR SFA iPHEP UMR CNRS 7262 Bât B35 TSA 51106 6 rue Michel Brunet F 86073 Poitiers Cedex 9 France

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