any large extinct scorpion-like aquatic arthropod of the group Eurypterida, of Palaeozoic times, thought to be related to the horseshoe crabs
Word origin
C19: from New Latin Eurypterida, from eury- + Greek pteron wing, feather
eurypterid in American English
(juˈrɪptərˌɪd)
noun
any of an extinct order (Eurypterida) of large, aquatic arthropods of the PaleozoicEra, similar to the horseshoe crab and sometimes reaching a length of c. 1.8 m (c. 6 ft)
Word origin
< ModL Eurypterida < Gr eurys, broad + pteron, feather, wing: so named from a pair of broad swimming appendages