ˌyu̇rə̇(p)ˈterədə, -u̇rə̇(- noun plural
Usage: capitalized
Etymology: New Latin, from Eurypterus, included genus (from eury- + -pterus ) + -ida
: an order of aquatic Paleozoic arthropods commonly forming with the related king crabs the class Merostomata, having a cephalothorax with six pairs of limbs of which the last pair were usually shaped like paddles and a tapering abdomen of 13 segments, and including the largest known arthropods, some exceeding 6 feet in length