Eurypterids belong to an extinct from of arthropods that were found in the Ordovician to the Permian.  They are also known as 'Sea Scorpions', although the similarities are largely superficial.   Although fossil specimens of this species are rare, the finds are often spectacular.  As well as body fossils, information can be gathered from trace fossils.  In 1948 trackways from the Shenango Sandstone formation, in Pennsylvania, measuring 79cm in width were discovered.  They were described as eurypterid trace fossils, although from which species is unknown, as it appears most Devonian-Carboniferous eurypterids were too small to have made them.

During the late Permian the eurypterids became extinct.  The Late permian extinction is known as a mass extinction, where 54% of all marine families became extinct.  As well as the eurypterids, many other species became extinct including tabulate and rugose corals, conularids, several gastropod groups, some ostracodes, ammonites, brachiopods, crinoids and the last few remaining trilobites.