The two eurypterid suborders, Eurypterina and Stylonurina, are separated primarily by the morphology of their final pair of appendages. In the Stylonurina, this appendage takes the form of a long and slender walking leg, while in the Eurypterina, the leg is modified and broadened into a swimming paddle. Other than the swimming paddle, the legs of many eurypterines were far too small to do much more than allow them to crawl across the sea floor. In contrast, a number of stylonurines had elongated and powerful legs that might have allowed them to walk on land (similar to modern crabs).