Scientists have discovered the fossilised remains of a giant sea scorpion which lived 467 million years ago during a dig in north-east Iowa. The Pentecopterus decorahensis - named after an ancient Greek ship rowed by 50 oarsmen during the Trojan War - grew to nearly six feet. With an exoskeleton "helmet" which shielded its head, a sleek narrow body, large limbs for grasping prey and a paddle-like leg used to swim, the sea scorpion was one of the top ocean predators of its time.