Meganeura was a giant dragonfly-like insect that lived about 300 million years ago during the Late Carboniferous. Fossils of Meganeura monyi indicate an estimated wingspan of roughly 65–70 centimeters (26–28 inches). It was not a true modern dragonfly, however, and scientists no longer agree that high atmospheric oxygen alone explains why some Paleozoic insects became enormous.
Key takeaways
- Meganeura belonged to Meganisoptera, commonly called griffinflies, an extinct group related to modern dragonflies and damselflies.
- Meganeura monyi is reconstructed with a wingspan of approximately 65–70 cm.
- Its fossils come from Late Carboniferous deposits at Commentry, France, dating to roughly 300 million years ago.
- Oxygen levels were elevated during parts of the late Paleozoic, but oxygen is not a complete or uncontested explanation for insect gigantism.
- Its exact diet and hunting behavior cannot be observed directly; reconstructions are based on anatomy and comparison with related predatory insects.
What was Meganeura?
Meganeura was a genus of predatory flying insects known from fossils in France. The best-known species, Meganeura monyi, was described from the coal-bearing rocks of Commentry during the late nineteenth century. Its name is often translated loosely as “large-veined,” referring to the conspicuous network of veins preserved in its wings.
Popular articles usually call it a “giant dragonfly,” which is useful as a visual comparison but not exact taxonomy. Meganeura belonged to the extinct order Meganisoptera—griffinflies—which sits outside the crown group containing living dragonflies and damselflies. The Natural History Museum describes these animals as early dragonfly-like insects rather than modern dragonflies enlarged to impossible size.
How large was Meganeura?
The famous estimate for Meganeura monyi is a wingspan of about 65–70 cm. France’s Muséum national d’Histoire naturelle depicts it at about 70 cm across, based on the large fossil wings found at Commentry. That span is comparable to the length of a small crow from beak to tail, but saying it was “crow-sized” can be misleading: the insect’s long, narrow body would have weighed far less than a bird with a similar overall span.
| Feature | Evidence-based interpretation |
|---|---|
| Wingspan | Approximately 65–70 cm for M. monyi |
| Age | Late Carboniferous, roughly 300 million years ago |
| Group | Meganisoptera, an extinct griffinfly lineage |
| Body mass | Uncertain and model-dependent |
| Flight style | Reconstructed from wings and aerodynamic models, not directly observed |
Meganeura was among the largest known flying insects, but it was not necessarily the absolute record holder. The Permian griffinfly Meganeuropsis permiana is commonly reconstructed with an equal or slightly greater wingspan. Fossil incompleteness and different reconstruction methods make rigid rankings less useful than the broader conclusion: griffinflies evolved wingspans far beyond those of living insects.
Did high oxygen make giant insects possible?
For decades, the leading explanation connected giant Paleozoic insects with elevated atmospheric oxygen. Insects deliver oxygen through a branching tracheal system rather than lungs, and Earth-system models have estimated that oxygen may have peaked near 30–35% during parts of the Permo-Carboniferous—well above today’s approximately 21%.
That correlation remains scientifically important, and experiments show that oxygen can influence insect growth and performance. But correlation is not proof that oxygen alone set the maximum body size. A 2012 analysis found that oxygen and insect size sometimes became decoupled through geological time, suggesting that ecology and competition also mattered.
The debate shifted further in 2026. A Nature study measuring tracheoles in flight muscle across 44 living insect species—and extending the analysis to giant fossil griffinflies—concluded that oxygen delivery through this part of the respiratory system does not impose the expected size constraint. High oxygen may still have affected flight, development or ecology, but the simple statement “more oxygen caused giant insects” is now too confident.
What did Meganeura eat?
Meganeura is generally reconstructed as an aerial predator. Its large compound eyes, strong mandibles and relationship to other predatory odonatopterans support a diet that probably included insects. Claims that it routinely hunted small amphibians are possible but speculative: no direct gut contents or feeding traces establish amphibians as regular prey.
Likewise, artists often show Meganeura weaving through dense coal forests. The Natural History Museum notes that such a wide-winged animal may have favored open wetlands and marshes where maneuvering space was greater. Paleoart therefore represents informed interpretation, not a photograph of a fully known ecosystem.
Why did giant griffinflies disappear?
Meganisopterans survived beyond the Carboniferous and remained diverse into the Permian. They disappeared by the end of the Permian and are unknown from the Triassic. Declining oxygen has often been proposed as a major cause, but the extinction occurred amid enormous environmental and ecological change culminating in the end-Permian mass extinction.
Later in insect evolution, competition and predation from flying vertebrates probably influenced maximum insect size. A broad fossil analysis found that the relationship between oxygen and insect size weakened as birds diversified, indicating that biological interactions can override atmospheric opportunity. No single variable explains every rise and fall in insect size across hundreds of millions of years.
Frequently asked questions
Was Meganeura a dragonfly?
Not in the modern sense. It was a griffinfly in the extinct order Meganisoptera, a close relative of the broader lineage that includes living dragonflies and damselflies.
Was Meganeura the largest insect ever?
It was among the largest known flying insects. Some specimens assigned to Meganeuropsis may have had an equal or slightly larger wingspan, while the giant arthropod Arthropleura was much longer but could not fly.
Could Meganeura live in today’s atmosphere?
We do not know. Modern oxygen levels, air density, climate, food webs and competition all differ from the late Paleozoic. Recent research also indicates that tracheolar oxygen supply alone would not necessarily prevent a giant insect body plan.
References
- Muséum national d’Histoire naturelle: Meganeura monyi
- Natural History Museum: Griffinflies
- Nature: Oxygen supply through the tracheolar–muscle system does not constrain insect gigantism
- PNAS: Environmental and biotic controls on insect body size
- Proceedings B: Atmospheric oxygen level and insect body size
- Integrative and Comparative Biology: Griffinfly gigantism and flight power