Claim: Reaching up to 3.7 metres (12.1 ft) from claw to claw, the Japanese spider crab  can weigh up to 19 kilograms (42 lb).
Evidence: The Japanese spider crab has the greatest leg span of any arthropod, reaching up to 3.7 metres (12.1 ft) from claw to claw. The body may grow to a size of 40 cm (16 in) in carapace width and the whole crab can weigh up to 19 kilograms (42 lb)—second in mass only to the American lobster among all living arthropod species.