The Eumetabola (Endopterygota (also known as Holometabola) plus Paraneoptera) have the highest number of species of any clade, and greatly contribute to animal species biodiversity. The palaeoecological circumstances that favoured their emergence and success remain an intriguing question. Recent molecular phylogenetic analyses have suggested a wide range of dates for the initial appearance of the Holometabola, from the Middle Devonian epoch (391 million years (Myr) ago) to the Late Pennsylvanian epoch (311 Myr ago), and Hemiptera (310 Myr ago). Palaeoenvironments greatly changed over these periods, with global cooling and increasing complexity of green forests. The Pennsylvanian-period crown-eumetabolan fossil record remains notably incomplete, particularly as several fossils have been erroneously considered to be stem Holometabola (Supplementary Information); the earliest definitive beetles are from the start of the Permian period. The emergence of the hymenopterids, sister group to other Holometabola, is dated between 350 and 309 Myr ago, incongruent with their current earliest record (Middle Triassic epoch). Here we describe five fossils--a Gzhelian-age stem coleopterid, a holometabolous larva of uncertain ordinal affinity, a stem hymenopterid, and early Hemiptera and Psocodea, all from the Moscovian age--and reveal a notable penecontemporaneous breadth of early eumetabolan insects. These discoveries are more congruent with current hypotheses of clade divergence. Eumetabola experienced episodes of diversification during the Bashkirian-Moscovian and the Kasimovian-Gzhelian ages. This cladogenetic activity is perhaps related to notable episodes of drying resulting from glaciations, leading to the eventual demise in Euramerica of coal-swamp ecosystems, evidenced by floral turnover during this interval. These ancient species were of very small size, living in the shadow of Palaeozoic-era 'giant' insects. Although these discoveries reveal unexpected Pennsylvanian eumetabolan diversity, the lineage radiated more successfully only after the mass extinctions at the end of the Permian period, giving rise to the familiar crown groups of their respective clades.

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Two different patterns of wing venation are currently supposed to be present in each of the three orders of Paraneoptera. This is unlikely compared with the situation in other insects where only one pattern exists per order. We propose for all Paraneoptera a new and unique interpretation of wing venation pattern, assuming that the convex cubitus anterior gets fused with the common stem of median and radial veins at or very near to wing base, after separation from concave cubitus posterior, and re-emerges more distally from R + M stem. Thereafter, the vein between concave cubitus posterior and CuA is a specialized crossvein called "cua-cup," proximally concave and distally convex. We show that despite some variations, that is, cua-cup can vary from absent to hypertrophic; CuA can re-emerge together with M or not, or even completely disappear, this new interpretation explains all situations among all fossil and recent paraneopteran lineages. We propose that the characters "CuA fused in a common stem with R and M"and "presence of specialized crossvein cua-cup" are venation apomorphies that support the monophyly of the Paraneoptera. In the light of these characters, we reinterpret several Palaeozoic and early Mesozoic fossils that were ascribed to Paraneoptera, and confirm the attribution of several to this superorder as well as possible attribution of Zygopsocidae (Zygopsocus permianus Tillyard, 1935) as oldest Psocodea. We discuss the situation in extinct Hypoperlida and Miomoptera, suggesting that both orders could well be polyphyletic, with taxa related to Archaeorthoptera, Paraneoptera, or even Holometabola. The Carboniferous Protoprosbolidae is resurrected and retransferred into the Paraneoptera. The genus Lithoscytina is restored. The miomopteran Eodelopterum priscum Schmidt, 1962 is newly revised and considered as a fern pinnule. In addition, the new paraneopteran Bruayaphis oudardi gen. nov. et sp. nov. is described fromthe Upper Carboniferous of France (see Supporting Information).

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Abstract. Insects dominate Earth by their diversity, and the most are Holometabola. Therefore, the holometabolous development characterised by a pupal stage between larvae and adult seems to be linked with the extensive radiation of insects. Holometaboly is suspected to appear in the carboniferous period, however until now fossils have not brought univocal evidence. The discovery in the Carboniferous (Early Langsettian, circa 310 mya, Bashkirian Stage) of France of the earliest Holometabola attributed to the Permian amphiesmenopteran or antliophoran family Protomeropidae brings the fi rst irrefutable evidence that holometaboly existed in the Carboniferous. Given the climatic data of France at this period, this discovery contradicts the traditional scenarii of a relation between the acquisition of endopterygote pupal stage and climatic global cooling during Late Carboniferous and Early Permian. This example illustrates the hypothesis that a new, apparently more effi cient, biological innovation is not always suffi cient to guarantee the 'evolutionary success' of the concerned clade. Ecological opportunities have to be considered as well for this innovation success.Résumé. Le plus ancien insecte holométabole du Carbonifère : une innovation cruciale au succès retardé (Insecta : Protomeropina : Protomeropidae). Les insectes dominant la Terre par leur diversité et les plus diversifi és sont les Holometabola. Le type de développement holométabole caractérisé par un stade pupal entre la larve et l'adulte semble lié à cette réussite radiative. L'holométabolie est suppose apparaître au Carbonifère, mais aucun fossile non équivoque n'est encore connu. La découverte dans le Carbonifère (Langséttien inférieur, environs 310 M.a., Bashkirien) de France du premier Holometabola non ambigu, attribué à la famille Protomeropidae, Amphiesmenoptera ou Antliophora permiens, apporte la première preuve irréfutable que l'holométabolie existait au Carbonifère. Etant donné les conditions climatiques en France à l'époque, cette découverte contredît les scenarii traditionnels d'une relation entre l'acquisition du stade pupal endoptérygote et le refroidissement climatique global de la fi n du Carbonifére et du Permien inférieur. Cet exemple illustre l'hypothèse qu'une innovation biologique en apparence plus 'effi cace' n'est pas toujours suffi sante pour expliquer le succès évolutif du clade concerné.

To better understand insect evolution, fossils – mainly known by their wings – must be used as terminals in phylogenetic analyses. Such analyses are, however, rarely performed because of a lack of consensus on the homology of venation in insects. Researchers do not agree with the current concept on the exact number and identity of the main veins. Here, we confirm the presence, which has been in question since the early 20th century, of an independent main postcubital vein (PCu vein) between the cubital and anal veins (29 fossil and extant examined orders; > 85% of observed insects). The PCu vein corresponds to the so‐called vein 1A or first anal vein. It is easily identified by the unique shape of its bulla. It may have several branches and be partially fused with the cubital and anal veins. Once the PCu vein was identified, we reconsidered as an example the particular case of the Phasmatodea, showing that extant stick insects have a unique venation among insects, with a reduced median vein and a simple cubital vein adjacent or fused to the PCu vein. This study is a new approach towards resolving wing vein homology issues, crucial for future large‐scale phylogenetic analyses in insects combining extant and extinct taxa.

The appearance of wings in insects, early in their evolution [1], has been one of the more critical innovations contributing to their extraordinary diversity. Despite the conspicuousness and importance of wings, the origin of these structures has been difficult to resolve and represented one of the "abominable mysteries" in evolutionary biology [2]. More than a century of debate has boiled the matter down to two competing alternatives-one of wings representing an extension of the thoracic notum, the other stating that they are appendicular derivations from the lateral body wall. Recently, a dual model has been supported by genomic and developmental data [3-6], representing an amalgamation of elements from both the notal and pleural hypotheses. Here, we reveal crucial information from the wing pad joints of Carboniferous palaeodictyopteran insect nymphs using classical and high-tech techniques. These nymphs had three pairs of wing pads that were medially articulated to the thorax but also broadly contiguous with the notum anteriorly and posteriorly (details unobservable in modern insects), supporting their overall origin from the thoracic notum as well as the expected medial, pleural series of axillary sclerites. Our study provides support for the formation of the insect wing from the thoracic notum as well as the already known pleural elements of the arthropodan leg. These results support the unique, dual model for insect wing origins and the convergent reduction of notal fusion in more derived clades, presumably due to wing rotation during development, and they help to bring resolution to this long-standing debate.