Meganisoptera is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

order of large dragonfly-like insects, informally known as griffenflies or (incorrectly) as giant dragonflies. The order was formerly named Protodonata, the "proto-Odonata", for their similar appearance and supposed relation to modern Odonata ( damselflies and dragonflies). They range in Palaeozoic ( Late Carboniferous to Late Permian) times. Though most were only slightly larger than modern dragonflies, the order includes the largest known insect species, such as the late Carboniferous '' Meganeura monyi'' and the even larger early Permian '' Meganeuropsis permiana'', with wingspans of up to .

The forewings and hindwings are similar in venation (a primitive feature) except for the larger anal (rearwards) area in the hindwing. The forewing is usually slenderer and slightly longer than the hindwing. Unlike the true dragonflies, the Odonata, they had no pterostigmata, and had a somewhat simpler pattern of veins in the wings. Most specimens are known from wing fragments only; with only a few as complete wings, and even fewer (of the family Meganeuridae) with body impressions. These show a globose head with large dentate

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

s, strong spiny legs, a large thorax, and long and slender dragonfly-like abdomen. Like true dragonflies, they were presumably predators. A few

nymph A nymph (; ; sometimes spelled nymphe) is a minor female nature deity in ancient Greek folklore. Distinct from other Greek goddesses, nymphs are generally regarded as personifications of nature; they are typically tied to a specific place, land ...

s are also known, and show mouthparts similar to those of modern dragonfly nymphs, suggesting that they were also active aquatic predators. Although sometimes included under the dragonflies, the Meganisoptera lack certain distinctive wing features that characterise the Odonata. point out that the colloquial term "giant dragonfly" is therefore misleading, and suggest "griffenfly" instead.

Size

Controversy has prevailed as to how insects of the Carboniferous period were able to grow so large. The way

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

is diffused through the insect's body via its tracheal breathing system (see

Respiratory system of insects An insect's respiratory system is the system with which it introduces respiratory gases to its interior and performs gas exchange. Air enters the respiratory systems of insects through a series of external openings called Spiracle (arthropods), ...

) puts an upper limit on body size, which prehistoric insects seem to have well exceeded. It was originally proposed in that ''Meganeura'' was only able to fly because the atmosphere at that time contained more oxygen than the present 20%. This theory was dismissed by fellow scientists, but has found approval more recently through further study into the relationship between gigantism and oxygen availability. If this theory is correct, these insects would have been susceptible to falling oxygen levels and certainly could not survive in the modern atmosphere. Other research indicates that insects really do breathe, with "rapid cycles of tracheal compression and expansion". Recent analysis of the flight energetics of modern insects and birds suggests that both the oxygen levels and air density provide a bound on size. A general problem with all oxygen related explanations of giant griffenflies is the circumstance that very large Meganeuridae ('' Arctotypus'' sp.) with a wingspan of 45 cm also occurred in the Upper Permian of Lodève in France, when the oxygen content of the atmosphere was already much lower than in the

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

and Lower Permian. suggested that the lack of aerial vertebrate predators allowed pterygote insects to evolve to maximum sizes during the Carboniferous and Permian periods, maybe accelerated by an " evolutionary arms race" for increase in body size between plant-feeding

Palaeodictyoptera The Palaeodictyoptera are an extinct order of medium-sized to very large, primitive Palaeozoic paleopterous insects. They are informative about the evolution of wings in insects. Overview They were characterized by beak-like mouthparts, used ...

and meganeurids as their predators.

Families and genera

These families belong to the order Meganisoptera: * Aulertupidae Zessin & Brauckmann 2010 * Kohlwaldiidae Guthörl 1962 * Meganeuridae Handlirsch 1906 * Namurotypidae Bechly 1996 * Paralogidae Handlirsch 1906 These genera belong to the order Meganisoptera, but have not been placed in families: * '' Alanympha'' Kukalova-Peck 2009 * '' Asapheneura'' Pruvost 1919 * '' Dragonympha'' Kukalova-Peck 2009 * '' Palaeotherates'' Handlirsch 1906 * '' Paralogopsis'' Handlirsch 1911 * '' Schlechtendaliola'' Handlirsch, 1919 * '' Typoides'' Zalessky 1948

Notes

References

Bibliography

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External links

Phylogenetic Systematics of Odonata
{{Taxonbar, from1=Q164689, from2=Q56479261 Carboniferous insects Permian insects Pennsylvanian first appearances Lopingian extinctions Extinct insect orders Odonatoptera