Meganeura

Way back, 300 million years back, there was a lot more Oxygen in the air than there is now. The reason for this is that plants essentially exploded on to the scene, taking in large amounts of Carbon Dioxide and expelling huge quantities of Oxygen in return. But while plants were covering the earth, animals, especially large Oxygen sucking land animals, just weren't there yet. This led to higher Oxygen percentages (around 32%, as compared to today's 21%).

Model of Meganeura

And what happens when you have higher Oxygen percentages? Larger bugs! Insects have a tracheal breathing system, which means that they take in all of their air through tracheae in their skin. This further means they can only grow as large as they amount of Oxygen they can take in. More Oxygen = larger sizes.

Meganeura was an example of one of the giants that popped up during this time. It was an absolutely gigantic dragonfly, with a wingspan of over 2.5ft! In comparison, the largest dragonfly today measures in at only 7.5in! Meganeura monyi, one of three uncovered species, is the largest flying insect species ever found.

Like modern Dragonflies, Meganeura was a predator. It fed on other insects and arthropods, as well as small amphibious vertebrates. Keep in mind though that Meganeura is only the largest flying arthropod. Other massive invertebrates crawled about during time (I'm looking at you Arthropleura), which means that this huge critter may have been hunting things even larger than itself! 

The entire Order that Meganeura belonged to is now extinct, due to the climate and evolutionary changes that led to a decrease in atmospheric Oxygen. Fossilized specimens have been found in England and France.

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Status : Extinct since the Carboniferous Period, around 300 million years ago

Location : Europe

Size : Wingspan up to 2.5ft (75cm)

Classification : Phylum : Arthropoda -- Class : Insecta -- Order : †Meganisoptera
Family : †Meganeuridae -- Genus : †Meganeura