Was the giant prehistoric insect Meganeura actually a victim of its own massive size?
In short: With a wingspan reaching up to 75 centimetres, Meganeura is the iconic giant of the Carboniferous skies. Yet, these ancient predators were likely clumsy fliers compared to modern dragonflies. New research suggests their massive bodies created a physiological struggle, forcing them to spend much of their time simply resting to breathe.
Discovered in the coal mines of Commentry, France, in 1880, Meganeura monyi remains one of the largest flying insects ever known. While often called a giant dragonfly, it belongs to the extinct order Meganisoptera, or 'griffenflies.' These insects possessed large compound eyes and spiny legs designed for capturing prey, much like their modern relatives. However, their anatomy was distinct; they lacked the specialized wing structures that allow modern dragonflies to make abrupt, agile turns, suggesting a less maneuverable flight style.
The mystery of how Meganeura reached such proportions has sparked intense debate. A long-standing hypothesis suggested that higher atmospheric oxygen levels in the Carboniferous period enabled their gigantism. However, this is contested by the presence of other large meganisopterans in the Late Permian, when oxygen levels were significantly lower. A 2026 study by Edward P. Snelling and colleagues further challenged the oxygen-size link, finding no evidence that larger invertebrates required different tracheal structures to manage oxygen diffusion.
Alternative theories point to an evolutionary arms race or the absence of aerial vertebrate predators. Paleontologist Günter Bechly proposed that the rise of agile, flying tetrapods like pterosaurs eventually created a predatory pressure that these giant insects could not survive. Meanwhile, researchers like Alan E. R. Cannell have explored the physical constraints of their flight. Because of their size, Meganeura may have relied on short bursts of activity, potentially struggling with thermoregulation and the need to oxygenate tissues, which would have limited their ability to maintain the constant, high-energy flight seen in modern dragonflies.
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- Summary by Intellect · source: Meganeura
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