Jaekelopterus (named for paleontologist Otto Jaekel + 'wing') was a predatory arthropod from the group informally known as 'sea scorpions'. Despite this name, it more likely lived in fresh water. Its type species is the largest arthropod yet discovered, at over two metres (over 7 feet) in length. Its eyes indicate it was an active predator, perhaps even an apex predator. It had excellent vision, with eyes similar to that of horseshoe crabs. Its vision improved as it aged.

(Devonian, 410.8–402.5 million years ago)