X-ray microtomography of the late Carboniferous whip scorpions (Arachnida, Thelyphonida) <i>Geralinura britannica</i> and <i>Proschizomus petrunkevitchi</i>

Whip scorpions (Thelyphonida) and schizomids (Schizomida) are closely related arachnid orders, whose low species diversity compared to other groups is reflected in a limited fossil record. Here we investigate two key whip from the British Middle Coal Measures of Coseley, Staffordshire (late Carboniferous, c. 315 Ma), UK, using X-ray microtomography, incorporate taxa into an updated phylogeny. Geralinura brittanica Pocock, Citation1911 unequivocal scorpion, pedipalps closer modern condition than previously assumed. The trochanter bears dorsal flange with prodorsal teeth, whole pedipalp rendered subchelate by presence at least patellar apophysis. These results suggest high degree stasis since late genus Geralinula Scudder, Citation1884 within crown-group; i.e. extant family Thelyphonidae. Proschizomus petrunkevitchi Dunlop Horrocks, Citation1996 lacks median eyes, character shared Schizomida, but unlike also has tibial apophyses; albeit appendage articulating angle 45° rather horizontally as living scorpions, or vertically schizomids. Our phylogeny refutes previous hypothesis that P. stem-schizomid, places it among instead. However, may have branched early scorpion lineage, thus its morphology might reflect plesiomorphic arrangement which were transitioning more leg-like fully raptorial claw-like set prey-catching appendages.