The whip scorpions (Arachnida: Uropygi) from the Pennsylvanian Coal Measures of Mazon Creek, Illinois, USA are restudied. Four Mazon Creek uropygid specimens have previously been described and a fifth is added here. Contrary to earlier reports, none of the specimens lack eyes and the sternum is similarly shaped in all the specimens. Consequently, the two younger names, Geralinura similis Petrunkevitch, 1913 and G. gigantea Petrunkevitch, 1913 are here treated as junior synonyms of G. carbonaria Scudder, 1884. The morphology of the pedipalps is more like those of some modern amblypygids, being spiniferous and non-chelate, suggesting the subchelate palps found in all Recent whip scorpions is an apomorphy not yet incorporated into the bodyplan of G. carbonaria. Indeed, subchelate palps also seem to be absent in other species of this age. For completeness, we summarise here the six Pennsylvanian whip scorpions currently recognised—including sketch reconstructions—with comments on further differences between the Paleozoic and living taxa. Geralinura Scudder, 1884 is reserved for G. carbonaria and the British species G. britannica Pocock, 1911. Prothelyphonus Frič, 1904 is reinstated for the Czech species P. bohemicus (Kušta, 1884). Parageralinura gen. nov. is proposed for the widely overlooked Dutch species P. neerlandica (Laurentiaux-Vieria and Laurentiaux, 1961) and the German species P. naufraga (Brauckmann and Koch, 1983). All the Coal Measures whip scorpion genera are treated here as plesion taxa, basal to the Thelyphonidae, which can be defined as whip scorpions with a fully subchelate pedipalp, the chelae formed from large and distinct patellar and tibial apophyses.