Any of various large segmented aquatic arthropods of the order Eurypterida that existed from the Ordovician Period to the Permian Period, having a long tail often with a spinelike appendage at the tip.
Any of an extinct order (Eurypterida) of large, aquatic arthropods of the Paleozoic Era, similar to the horseshoe crab and sometimes reaching a length of c. 1.8 m (c. 6 ft)
Origin of eurypterid
- From New Latin Eurypterida order name from Eurypterus genus name eury– Greek pteron wing –pter
From American Heritage Dictionary of the English Language, 5th Edition