The Late Paleozoic acquisition of wings in insects represents one of the key steps in arthropod evolution. While the origin of wings has been a contentious matter for nearly two centuries, recent evolutionary developmental studies suggest either the participation of both tergal and pleural tissues in the formation of wings1 or wings originated from exites of the most proximal leg podite incorporated into the insect body wall.2 The so-called "dual hypothesis" for wing origins finds support from studies of embryology, evo-devo, and genomics, although the degree of the presumed contribution from tergal and pleural tissues differ.3-6 Ohde et al.,7 confirmed a major role for tergal tissue in the formation of the cricket wing and suggested that "wings evolved from the pre-existing lateral terga of a wingless insect ancestor." Additional work has focused on identifying partial serially homologous structures of wings on the prothorax8,9 and abdominal segments.10 Thus, several studies have suggested that the prothoracic horns in scarab beetles,9 gin traps of tenebrionid and scarab beetle pupae,11,12 or abdominal tracheal gills of mayfly larvae1,13 evolved from serial homologues of wings. Here, we present critical information from abdominal lateral outgrowths (flaps) of Paleozoic palaeodictyopteran larvae, which show comparable structure to thoracic wings, consisting of cordate lateral outgrowths antero-basally hinged by muscle attachments. These flaps therefore most likely represent wing serial homologues. The presence of these paired outgrowths on abdominal segments I-IX in early diverging Pterygota likely corresponds to crustacean epipods14,15 and resembles a hypothesized ancestral body plan of a "protopterygote" model.

Department of Zoology Faculty of Science Charles University Viničná 7 CZ 128 00 Praha 2 Czech Republic

Division of Entomology Natural History Museum and Department of Ecology and Evolutionary Biology 1501 Crestline Drive Suite 140 University of Kansas Lawrence KS 66045 USA; Division of Invertebrate Zoology American Museum of Natural History Central Park West at 79th Street New York NY 10024 5192 USA

Institut de Systématique Évolution Biodiversité Muséum national d'Histoire naturelle CNRS Sorbonne Université EPHE Université des Antilles CP50 57 rue Cuvier 75005 Paris France

Institute of Biology Pedagogical University of Kraków Podbrzezie 3 31 054 Kraków Poland

Institute of Systematics and Evolution of Animals Polish Academy of Sciences ul Sławkowska 17 31 016 Kraków Poland

Curr Biol. 2022 Aug 8;32(15):R851-R853. doi: 10.1016/j.cub.2022.06.087. PubMed

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Thoracic and abdominal outgrowths in early pterygotes: a clue to the common ancestor of winged insects?