a giant fossil marine arthropod of a group occurring in the Palaeozoic era. They are related to horseshoe crabs, and resemble large scorpions with a terminal pair of paddle-shaped swimming appendages.
Subclass Eurypterida, class Merostomata, subphylum Chelicerata
Origin:
late 19th century: from modern Latin Eurypterus (genus name), from eury- + Greek pteron 'wing' + -id2
eurypterid in other Oxford dictionaries
Definition of eurypterid in the US English dictionary
