Meganeura was a genus of dragonfly-like insects that lived during the late part of the Paleozoic era, during the Carboniferous and Permian periods. It includes the largest known flying insect species, including Meganeura monyi, Meganeura americana, and Meganeuropsis permiana, a closely related species. These so-called "griffinflies" had wingspans of more than 75 cm (2.5 ft). Some griffinflies persisted into the Triassic and possibly the early Triassic period.
Meganeura and its relatives are considered griffinflies rather than dragonflies because they derive from a different lineage, despite evolutionary convergence and similarity. Meganeura and its relatives are part of order Protodonata, which means "primitive dragonfly." They are not considered true dragonflies because they lack several distinctive features found in dragonflies. For instance, the vein pattern on the front and back wings of Meganeura is almost the same, in contrast to modern dragonflies which have vein patterns that very.
Meganeura means "large veins," a reference to the thick network of veins which supported its wings like a skeleton, also providing oxygen. Meganeura was an obligate carnivore, and besides having its pick of practically any other insect, it also ate small amphibians and other vertebrates. Frequenting the edges of ponds, streams, and other watercourses, Meganeura would have used its long legs to grasp prey and hold on to it. The legs were covered with small spines to prevent escape. Once caught, the griffinfly would have killed and consumed its prey with large, sharp mandibles.
Meganeura fossils have been found in France, the UK, Oklahoma, and other locales. In asking how Meganeura got to be so large, scientists have speculated that oxygen may be responsible. There were greater oxygen levels than today in the forests of the Carboniferous, which would have made it easier for insects to absorb oxygen from outside and keep themselves running. However, recent studies have found that insects may in fact have some mechanism of breathing, and hence would not entirely depend on ambient oxygen levels to survive. Other factors may be responsible for the lack of dragonfly-like predators of this size in the modern world.
The great size of Meganeura is a testament to the effectiveness of the basic dragonfly body plan. Modern dragonflies are actually the best insect fliers, capable of reaching speeds of 70 mph with excellent maneuverability, but the size of Meganeura makes it unlikely that it was this fast. It was still likely very fast and deadly.