Following close examination and the discovery of new fossil evidence, further genera would be split off from "Pterygotus". "P. rhenaniae" was classified as part of its own genus, "Jaekelopterus", by Charles D. Waterston in 1964. He considered the species sufficiently distinct from other "Pterygotus" species due to its supposedly segmented genital appendage (a feature later realized to be wrong), its narrow and long chelicerae, and its primary teeth being angled slightly anteriorly. Another species, "P. ventricosus", was classified as the separate genus "Ciurcopterus" in 2007 by O. Erik Tetlie and Derek E. G. Briggs, distinguished primarily by sharing several features with more basal pterygotioid eurypterids, such as its appendages being similar to those of "Slimonia".