When enormous dragonflies ruled the sky:
Life was never easy for small amphibians or average sized flying insects during the late Carboniferous and early Permian periods of the Paleozoic Era. As though the day to day requirement to feed and reproduce were not enough to worry about, the diminutive amphibian had to avoid hungry fishes when in the water, and apex predators like the therapsids (Titanophoneus as just one example) and pelycosaurs (Dimetrodon and kin) when on land. Large, hungry amphibians like Sclerocephalus were a danger whichever environment the tiny creature happened to occupy.
You would think that would be enough to contend with, and since pterosaurs were millions of years in the future as were predatory birds like herons, hawks and pelicans the little creature would be safe from above.
Not so. For, hovering aloft like the Apache attack helicopters they resemble were the gigantic dragonflies Meganeuropsis permiana.
Leave the fly swatter in the closet:
Probably the largest flying insect that ever lived, fossils of Meganeuropsis permiana have been discovered that have a wing span of just under 30 inches and a total body length of 17 inches. These were the largest creatures flying in the Carboniferous and Permian skies and like their smaller close relatives the modern dragonflies were voracious predators. Or perhaps more accurately, even more so.
The food required to produce the energy to keep this huge body aloft must have kept Meganeuropsis perpetually on the hunt. Modern dragonflies will attack tiny tadpoles and newly hatched fry; we can easily envision Meganeuropsis swooping down on anything up to chipmunk size that came to its attention. And of course, anything flying that was smaller than Meganeuropsis was fair game.
Raising a lot of questions:
Today there are no flying insects even close to the size of this ancient predator, for which we should probably be thankful. There is a school of thought that says that this creature should not have been able to fly at all.
The answer to how it did so lies more in the geography, climate and atmosphere of the Carboniferous and Permian periods than in the morphology of the huge insect itself. To simplify enormously; during most of the Carboniferous and Permian periods there existed one super continent, Pangaea, containing almost all of the earths land mass. An explosion of flora, all utilizing the photosynthetic process produced immense amounts of oxygen while binding enormous quantities of carbon dioxide. Over time this actually shifted the proportions of the earth’s gases.
Today, our atmosphere contains about 21% oxygen. It is estimated that Carboniferous-Permian atmospheres contained at least 30% and possibly as much as 35% oxygen, with a corresponding dip in the amount of free carbon dioxide. This, so the theory goes, permitted Meganeuropsis and its kin to breath efficiently, even though they do so through trachea and not through lungs and a circulatory system as we do. This would have kept the creatures oxygenated enough to fly.
Why did they go extinct?
On one level, this question is easily answered. The end of the Permian period was marked by one of the greatest mass extinctions ever known on our planet. Nearly everything that lived, died. That Meganeuropsis was among the casualties is no surprise. The deeper question of what caused the P/T extinction is a subject for intense debate, although once again it seems that massive impact from an extraterrestrial body may be to blame.
Whatever triggered the event of one fact we can be certain. The oxygen level of earths atmosphere, either as a by product of the extinction event itself or by some other mechanism that we do not as yet understand dropped precipitously. This alone would have sealed the fate of the great dragonflies forever.
Here is another interesting article: What is the lifespan of a dragonfly