"P. floridanus", recovered from deposits of Lochkovian age in Florida, extended the known range of eurypterids on the continent over 800 km (500 miles) south. Prior to its discovery, eurypterids in North America were only known from the northern parts of the continent, with New York State representing the most fossil-rich state. The remains of "P. floridanus" were first uncovered by G. Arthur Cooper in Suwannee County, Florida, and the fossils consist of a fixed ramus of the chelicera as well as fragments of the abdominal plates and tergites and were concluded to represent a new species of "Pterygotus" by Erik N. Kjellesvig-Waering in 1950. It most closely resembles "P. cobbi" and "P. barrandei", differing from "P. cobbi" in its more developed central tooth and the arrangement of the smaller teeth of the claws and from "P. barrandei" in that "P. floridanus" has a more slender ramus.