Illustration of eurypterid
eurypterid
noun
eu·ryp·ter·id yu̇-ˈrip-tə-rəd 
: any of an order (Eurypterida) of usually large aquatic Paleozoic arthropods resembling scorpions and related to the horseshoe crabs
called also sea scorpion
eurypterid adjective
Example Sentences
Recent Examples on the Web Mixopterids, the most remarkable of the eurypterid (sea scorpion) species, are known for their large limbs to capture prey. 
Naomi Ludlow, USA TODAY, 30 Oct. 2021
Naomi Ludlow, USA TODAY, 30 Oct. 2021 Word History
Etymology
ultimately from Greek eury- + pteron wing — more at feather
First Known Use
1871, in the meaning defined above