Meganeura - Meganeura

Meganeura is also read as Meganeura. It is a fossil insect discovered in a late Carboniferous layer of a coal mine in Commentry, France, around 1880. When many fragments were put together, it was found to be a huge insect with wings as long as 30 centimeters. Its shape and wing venation are similar to modern dragonflies, but it differs from modern dragonflies in that it lacks nodes, marginal patterns, and true arcuate veins on the wing venation. These primitive dragonflies were collectively called Proto-Odonata and distinguished from Odonata, but today they are often treated as the most primitive suborder of Odonata, the Meganeura. After its discovery in France, large species comparable to or even larger than this one were found in North America and other places, and these can be said to be the largest insects in history. In the middle of the Carboniferous period, insects that acquired wings and were the first animals to live in the air underwent great development and became large in size. There were relatively many large insects from this period, and the Meganeura species were the most extreme of them. Reconstructions of dragonfly-like bodies are often seen, but it is doubtful whether a dragonfly of this size and shape could have flew around as nimbly as modern dragonflies. The genus Meganeura only lived in the Carboniferous, but the group survived into the Permian.

[Fujiyama Ienori]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

メガニューラとも読む。1880年ころ、フランスのコマントリーCommentryにある炭坑の古生代石炭紀後期の地層で発見された化石昆虫で、多くの破片をつなぎあわせたところ、羽の長さが30センチメートルもある巨大な昆虫であることがわかった。形や翅脈(しみゃく)は現在のトンボに似ているが、翅脈に結節、縁紋、真の弧脈を欠く点でいまのトンボ類と異なる。このような原始的なトンボ類をあわせて原トンボ目としてトンボ目と区別してきたが、今日ではトンボ目のなかのもっとも原始的なメガネウラ亜目として扱われることが多くなった。フランスでの発見後、北アメリカなどでこれに匹敵するか、これを越すような大形種もみつかっており、これらは史上最大の昆虫といえる。石炭紀中ごろ、羽を獲得して動物として初めて空中をも生活域とした昆虫は、大発展をなし体も大形化した。この時代の昆虫には大形のものが比較的に多いが、その極がメガネウラ類であった。トンボ状の胴体の復元図をよくみかけるが、このような形態と大きさで、いまのトンボと同じように敏捷(びんしょう)に飛び回れたかどうかは疑わしい。メガネウラ属は石炭紀だけに生息したが、そのグループはペルム紀まで生き延びた。

［藤山家徳］

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