| Eurypteroid | a. [ Eurypterus + -oid. ] (Paleon.) Like, or pertaining to, the genus Euryperus. [ 1913 Webster ] |
| Eurypteroidea | ‖n. pl. [ NL. See Eurypteroid. ] (Paleont.) An extinct order of Merostomata, of which the genus Eurypterus is the type. They are found only in Paleozoic rocks. |