The eurypterids include the largest known arthropods ever to have lived. The largest, "Jaekelopterus", reached in length. Eurypterids were not uniformly large and most species were less than long; the smallest eurypterid, "Alkenopterus", was only long. Eurypterid fossils have been recovered from every continent. A majority of fossils are from fossil sites in North America and Europe because the group lived primarily in the waters around and within the ancient supercontinent of Euramerica. Only a handful of eurypterid groups spread beyond the confines of Euramerica and a few genera, such as "Adelophthalmus" and "Pterygotus", achieved a cosmopolitan distribution with fossils being found worldwide.