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eu·ryp·ter·id | \ yu̇-ˈrip-tə-rəd 
\
\Definition of eurypterid
: any of an order (Eurypterida) of usually large aquatic Paleozoic arthropods resembling scorpions and related to the horseshoe crabs
— called also sea scorpion
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Time Traveler for eurypterid
The first known use of eurypterid was in 1871
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