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.
