Both "Pterygotus anglicus" and "Jaekelopterus rhenaniae" had a very high visual acuity, which researchers could determine by observing a low IOA and a large number of lenses in their compound eyes. The chelicerae of "Pterygotus" were enlarged, robust and possessed a curved free ramus and denticles of different lengths and sizes, all adaptations that correspond to strong puncturing and grasping abilities in extant scorpions and crustaceans. The IOA values for both "Pterygotus" and "Jaekelopterus" match those of high level and active modern predatory arthropods, indicating that they represented visual and active predators.