12-447: The name Palaeoptera (from Greek παλαιός ( palaiós 'old') + πτερόν ( pterón 'wing')) has been traditionally applied to those ancestral groups of winged insects (most of them extinct) that lacked the ability to fold the wings back over the abdomen as characterizes the Neoptera . The Diaphanopterodea , which are palaeopteran insects, had independently and uniquely evolved
24-477: A plesiomorphic trait. These two orders belong to the infraclass Palaeoptera however, which is not included in Neoptera. As opposed to Neoptera, they cannot fold their wings over their back in the horizontal plane , only vertically (as damselflies do) if at all. Traditionally Exopterygota included all neopterans that show incomplete metamorphosis . More recently, there is increasing debate about how to subdivide
36-628: A superorder of insects of the subclass Pterygota in the infraclass Neoptera , in which the young resemble adults but have externally developing wings. They undergo a modest change between immature and adult, without going through a pupal stage. The nymphs develop gradually into adults through a process of moulting . The Exopterygota are a highly diverse insect superorder, with at least 130,000 living species divided between 15 orders . They include cockroaches , termites , grasshoppers , thrips , lice and stick insects , among many other types of insects. Exopterygota are distinguished from
48-442: A different wing-folding mechanism. Both mayflies and dragonflies lack any of the smell centers in their brain found in Neoptera . The complexities of the wing-folding mechanism, as well as the mechanical operation of the wings in flight ( indirect flight muscles ), are such that it clearly indicates the Neoptera are a monophyletic lineage. The problem is that the plesiomorphic absence of wing-folding does not necessarily mean
60-568: The Archaeognatha (jumping bristletails) and the Zygentoma ( silverfishes and firebrats ), two primitively wingless insect orders. Unlike Archaeognatha and Zygentoma, the pterygotes do not have styli or vesicles on their abdomen (also absent in some zygentomans), and with the exception of the majority of mayflies, are also missing the median terminal filament which is present in the ancestrally wingless insects. The oldest known representatives of
72-591: The Endopterygota (or Holometabola) by the way their wings develop. Endopterygota (meaning literally "internal winged forms") develop wings inside the body and undergo an elaborate metamorphosis involving a pupal stage. Exopterygota ("external winged forms") develop wings on the outside of their bodies without going through a true pupal stage, though a few have something resembling a pupa (e.g., Aleyrodidae ). Ephemeroptera (mayflies) and Odonata (dragonflies and damselflies) also have gradual wing development, this being
84-478: The Palaeodictyopteroidea themselves might be a paraphyletic assemblage of very basal Pterygota , too. As it stands, the relationship of the two living Paleopteran groups – Ephemeroptera (mayflies) and Odonata ( dragonflies and damselflies ) – to the Neoptera has not been resolved yet; there are three competing main hypotheses with many variations. In two of these – those that treat
96-551: The Palaeoptera form a natural group – they may simply be an assemblage containing all insects, closely related or not, that "are not Neoptera", an example of a wastebasket taxon . If the extinct lineages are taken into account, it seems likely that the concept of Palaeoptera will eventually be discarded or changed in content to more accurately reflect insect evolution. In any case, three main palaeopteran lineages, traditionally treated as superorders , are recognized. Of these,
108-545: The ephemeropteran or the odonatan lineage as closer to the Neoptera than to the other "palaeopterans" – the Palaeoptera appear to be paraphyletic . Winged insects Pterygota ( / ˌ t ɛ r ə ˈ ɡ oʊ t ə / terrə- GOH -tə Ancient Greek : πτερυγωτός , romanized : pterugōtós , lit. 'winged') is a subclass of insects that includes all winged insects and groups who lost them secondarily. Pterygota group comprises 99.9% of all insects. The orders not included are
120-610: The group appeared during the mid-Carboniferous, around 328–324 million years ago, and the group subsequently underwent rapid diversification. Claims that they originated substantially earlier during the Silurian or Devonian based on molecular clock estimates are unlikely based on the fossil record, and are likely analytical artefacts. Traditionally, this group was divided into the infraclasses Paleoptera and Neoptera . The former are nowadays strongly suspected of being paraphyletic , and better treatments (such as dividing or dissolving
132-438: The group) are presently being discussed . In addition, it is not clear how exactly the neopterans are related among each other. The Exopterygota might be a similar assemblage of rather ancient hemimetabolous insects among the Neoptera like the Palaeoptera are among insects as a whole. The holometabolous Endopterygota seem to be very close relatives, indeed, but nonetheless appear to contain several clades of related orders,
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#1732852068205144-538: The status of which is not agreed upon. The following scheme uses finer divisions than the one above, which is not well-suited to correctly accommodating the fossil groups. (probably paraphyletic) Superorder Exopterygota Superorder Endopterygota Neoptera orders incertae sedis Exopterygota For extinct groups and possible future splits, see text. The Exopterygota ( Ancient Greek ἔξω (éxō, “outside”) + πτερόν (pterón, “wing”) + Neo-Latin -ota (“having”)), also known as Hemimetabola , are
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