Three hundred million years ago, the largest insect ever known to humankind hunted in fern jungles and boasted an enormous wingspan of nearly 2.5 feet. Different from modern dragonflies in its size and other attributes, the Meganeura earned the title "prehistoric griffinfly" from scientists. The first Meganeura fossil, discovered in 1880, eventually led researchers to a group of mega-insects, including Meganeuropsis permiana and other massive dragonflies. These creatures hunted prey using their enormous eyes, toothed mandibles, and sharp legs.
This insect was only one of many massive prehistoric creatures. But atmospheric differences and a lack of flying predators allowed Meganeura to rule the skies for millions of years. Unlike other exotic insects that evolved defensive coloring to hide, Meganeura used its size to dominate prehistoric swamps.
But what caused the ancient insect to go extinct? Scientists still disagree.
Its Size Might Have Helped It Avoid Oxygen Poisoning
Many scientists agree the atmosphere's higher oxygen concentration helped prehistoric insects grow remarkably large. But newer research suggests creatures like Meganeura might have ballooned to enormous sizes to avoid oxygen poisoning. In the larval phase, dragonflies live in water. And during Meganeura's time, higher oxygen levels led to more oxygen that dissolved in the water; larval Meganeura would have absorbed that gas.
Because high oxygen levels can harm living creatures, Meganeura could have grown to avoid oxygen toxicity.
Some Theorize It Went Extinct Because Of Atmospheric Changes
Scientists believe a higher concentration of oxygen in the atmosphere let insects grow larger in the past. Researchers found a direct connection between oxygen levels and wingspans for over 10,000 fossilized insects spanning the past 320 million years.
Many of the biggest insects were lost during the Permian period, around 250 million years ago. The Permian Extinction wiped out 90% of species on Earth. It also coincided with a change in the Earth's atmosphere which saw oxygen levels decline.
One study suggested Meganeura might have been sluggish and underperforming in the thinner air; newer, faster species might have driven it to its end.
Others Argue That Dinosaurs Evolved Into Birds And Out-Hunted It
Large insects that survived the Permian Extinction may have faced a new threat: flying dinosaurs. When dinosaurs like the Archaeopteryx first took flight about 140 million years ago, insect wingspans got smaller. The first dino-bird hybrid preyed on large insects and competed with them for food sources.
As researcher Matthew Clapham explained, the competition saw the ancient birds triumph:
These large insects are [predacious] and they eat smaller insects. It's possible that birds may have also eaten small insects, as many modern birds do. If they are competing for the same resource, birds may have been better competitors for these food sources.
Meganeura Fossils Were First Discovered In France In 1880
Explorers uncovered the first Meganeura fossil in France in 1880. It took five years for researchers to name the creature, but in 1885, French paleontologist Charles Brongniart dubbed the massive prehistoric dragonfly Meganeura because of its large-veined wings.
Additional Meganeura fossils turned up in both France and England.