10 Terrifying Creatures That You’ll Be Glad Are Extinct

These guys certainly put the "dragon" in dragonfly. With a wingspan of up to 68cm (that's well over two feet, folks), if you had one of these winged giants buzzing up against your window, you'd certainly know about it.

Scientists disagree on how exactly a bunch of humble flying insects got to be the size of a small dog, but the theory that perpetuates is that it is due to high levels of oxygen present in the Earth's atmosphere during the Paleozoic Era. 

Far from daintily fluttering between flowers around ornamental ponds like their modern equivalents, these dragons may well have fed on frogs and even small mammals in order to maintain their massive bulk (presumably in between chugging protein shakes and doing another set of bicep curls).