Meganeura
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| Meganeura Fossil range: Late Carboniferous |
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 Meganeura
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| Meganeura monyi (C. Brongniart, 1893) |
Meganeura monyi was a prehistoric insect of the Carboniferous period (300 million years ago), resembling and related to the present-day dragonfly. With a wingspan of more than 75 cm (2.5 feet) wide, it was the largest known flying insect species to ever appear on Earth. (The Permian Meganeuropsis permiana is another contender). It was predatory, feeding on other insects and even small amphibians.
Fossils were discovered in the Stephanian Coal Measures of Commentry in France in 1880; in 1885, French paleontologist Charles Brongniart described and named the fossil. Another fine fossil specimen was found in Bolsover, Derbyshire, in 1979. The holotype is housed in the Muséum National d'Histoire Naturelle, Paris.
M. americana, discovered in Oklahoma in 1940, is represented by the largest complete insect wing ever found; it is conserved in the Harvard Museum of Natural History.[1]
Controversy has prevailed as to how insects of the Carboniferous period were able to grow so large. The way oxygen is diffused through the insect's body via its tracheal breathing system puts an upper limit on body size, which prehistoric insects seem to have well exceeded. It was originally proposed (Harlé & Harlé, 1911) 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 [2] If this theory is correct, these insect giants would have been perilously susceptible to falling oxygen levels and certainly could not survive in our modern atmosphere.
However, more recent research indicates that insects really do breathe, with "rapid cycles of tracheal compression and expansion".[3] If correct, then there is no need to postulate an atmosphere with higher oxygen partial pressure.
The word Meganeura means "large-veined", referring to the network of veins on the wings.
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[edit] Popular culture
- Meganeura appears briefly in BBC's Walking With Monsters in which it snatches a small reptile from a giant spider.
- Meganeura also appears in iTV's Prehistoric Park and lived in a big glass dome built for it.
- Meganula is an insect Kaiju based on this creature and is featured heavily in Godzilla vs. Megaguirus.
- A giant dragonfly that may have been Meganeura was featured briefly in the novel version of Jurassic Park.
- In the games Pokemon Diamond and Pearl, Yanma's evolved form Yanmega is based upon the ancient dragonfly, Meganeura.
- A modern-day dragonfly devolves into Meganeura after feeding on the fluid of an irradiated Coelacanth in the film Monster on the Campus.
[edit] Other usage
Meganeura is a scientific periodical about fossil insects.[4].
[edit] References
- ^ "Dragonfly: the largest complete insect wing ever found", Harvard Magazine November-December 2007:112.
- ^ Gauthier Chapelle and Lloyd S. Peck (May 1999). "Polar gigantism dictated by oxygen availability" (in English). Nature 399: 114-115. doi:. “Oxygen supply may also have led to insect gigantism in the Carboniferous period, because atmospheric oxygen was 30-35% (ref. 7). The demise of these insects when oxygen content fell indicates that large species may be susceptible to such change. Giant amphipods may therefore be among the first species to disappear if global temperatures are increased or global oxygen levels decline. Being close to the critical MPS limit may be seen as a specialization that makes giant species more prone to extinction over geological time.”
- ^ Westneat MW, Betz O, Blob RW, Fezzaa K, Cooper WJ, Lee WK. (January 2003). "Tracheal respiration in insects visualized with synchrotron x-ray imaging" (in English). Science 299: 558–560. doi:. “Insects are known to exchange respiratory gases in their system of tracheal tubes by using either diffusion or changes in internal pressure that are produced through body motion or hemolymph circulation. However, the inability to see inside living insects has limited our understanding of their respiration mechanisms. We used a synchrotron beam to obtain x-ray videos of living, breathing insects. Beetles, crickets, and ants exhibited rapid cycles of tracheal compression and expansion in the head and thorax. Body movements and hemolymph circulation cannot account for these cycles; therefore, our observations demonstrate a previously unknown mechanism of respiration in insects analogous to the inflation and deflation of vertebrate lungs.”
- ^ {http://www.ub.es/dpep/meganeura/meganeura.htm Meganeura.
[edit] External links
The Wikimedia Commons has media related to Meganeura.- Picture of life sized model of Meganeura monyi made for Denver Museum of Natural History.
