Three hundred million years ago giant insects lived on Earth during the Carboniferous period, with dragonflies having a wingspan of nearly a meter. ?

Scientists have discovered through the fossil record that giant species existed on Earth before the dinosaurs: giant arthropods from the Carboniferous period 300 million years ago, including oversized mayfly insects, scorpions. Spiders the size of a hanging orchid. And 5-foot-long millipedes, to name a few.

The most amazing of these would have to be the giant dragonflies, which could have wingspans of up to 2 ? feet (nearly 1 meter), as big as an eagle, making them the largest insects ever to have lived on Earth.Giant insects lived on Earth during the Carboniferous period 300 million years ago, and dragonflies had wingspans of nearly a meter. ?

Scientists have long speculated that perhaps changes in atmospheric oxygen levels played a key role in their rise and fall. Now, paleontologists are beginning to explore whether the rise and fall of these ancient dragonflies, cockroaches, and other super-sized insects, which were the size of today's eagles, had anything to do with the extraordinarily high oxygen levels. ?

In their report, the researchers note:

The concentration of oxygen in the Earth's atmosphere during the Carboniferous period was as high as 35 percent, much higher than the current 21 percent. Many arthropods absorb oxygen directly through microscopic tracheas that are spread throughout their musculature, rather than indirectly through the bloodstream, so the high oxygen content could have contributed to the evolution of insects toward larger size. ?