Hallipterus
Hallipterus is a genus of prehistoric eurypterid classified as part of the family Hardieopteridae. Description. "Hallipterus" was a gigantic Hardieopterid eurypterid. Though some previous estimates have placed its size at over 1.5 meters in length, these were likely excessive. Still, assigned specimens suggest a size of over 1 meter long. The carapace was subelliptical, greater in length than in width, with a prominent and unornamented marginal rim. The eyes were very small, close to each other and separated by a prominent median ridge with large ocelli at the posterior extremity. The chelicerae were simple and elongated. The first walking  legs possessed flat and movable spines. The rest of the legs and the opisthosoma remain unknown. Species. "Hallipterus" contains one valid species, "H. excelsior", from the Devonian of New York. Another species was once recognized from similarly aged deposits in Pennsylvania, ""H. lacoanus"", but it is today seen as synonymous with "H. excelsior".