The cheliceral morphology and visual acuity of the pterygotid eurypterids separates them into distinct ecological groups.
The primary method for determining visual acuity in arthropods is by determining the number of lenses in their compound eyes and the interommatidial angle (shortened as IOA and referring to the angle between the optical axes of the adjacent lenses).
The IOA is especially important as it can be used to distinguish different ecological roles in arthropods, being low in modern active arthropod predators.

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.

All known pterygotids (though they are so far unknown in Ciurcopterus) possessed cheliceral claws.
The first joint of the chelicerae, where it connects to the epistoma (a plate located on the prosoma, or "head"), would have been capable of turning the entire appendage in a twisting way, which has led researchers to conclude that the function of the chelicerae would not have been only, or even primarily, for defense but rather to capture and convey food to the mouth.
When captured, prey would need to be broken into smaller pieces to be able to fit into the mouth; eurypterid mouths were even less adapted to devour large pieces than mouths of modern crabs are.
The eurypterid walking appendages could not cut, transport or grasp anything, so these tasks would also likely fall to the chelicerae.
In crabs, the claws tear food apart and then transport the smaller pieces to the mouth.
Based on the feeding process seen in modern arthropods with chelicerae, one of the claws would hold the prey while the other would cut off pieces and transport it to the mouth with continuous and simple movements.
The cheliceral morphology and visual acuity of the pterygotid eurypterids separates them into distinct ecological groups. The primary method for determining visual acuity in arthropods is by determining the number of lenses in their compound eyes and the interommatidial angle (shortened as IOA and referring to the angle between the optical axes of the adjacent lenses). The IOA is especially important as it can be used to distinguish different ecological roles in arthropods, being low in modern active arthropod predators.
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.
All known pterygotids (though they are so far unknown in Ciurcopterus) possessed cheliceral claws. The first joint of the chelicerae, where it connects to the epistoma (a plate located on the prosoma, or "head"), would have been capable of turning the entire appendage in a twisting way, which has led researchers to conclude that the function of the chelicerae would not have been only, or even primarily, for defense but rather to capture and convey food to the mouth. When captured, prey would need to be broken into smaller pieces to be able to fit into the mouth; eurypterid mouths were even less adapted to devour large pieces than mouths of modern crabs are. The eurypterid walking appendages could not cut, transport or grasp anything, so these tasks would also likely fall to the chelicerae. In crabs, the claws tear food apart and then transport the smaller pieces to the mouth. Based on the feeding process seen in modern arthropods with chelicerae, one of the claws would hold the prey while the other would cut off pieces and transport it to the mouth with continuous and simple movements.
Pterygotus