Sea scorpions, or eurypterids, were the largest arthropods the world has ever seen and could grow to 2.5 metres long. They had a pair of pincers, and in some species these too could become very large. Sea scorpions were predators that were in their heyday in the Silurian and Devonian, though they survived into the Permian. The name sea scorpion is something of a misnomer, as they also inhabited freshwater and may have ventured on to land now and then. They are related to scorpions, horseshoe crabs and spiders.

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