The eurypterids (sea scorpions) include the largest known arthropod that ever lived (with the possible exception of Arthropleuridae). They are members of the extinct class Eurypterida (Arachnomorpha, Chelicerata) and predate the earliest fishes. The largest, such as Jaekelopterus, reached 2 m or more in length, but most species were less than 20 cm. They were formidable predators that thrived in warm shallow water in the Cambrian to Permian from 510 to 248 million years ago. Although called "se… (More on Eurypterid)