What modern organism did pterosaurs have a similar ecological role to and why?

Birds.

Explanation:

Pterosaurs are nothing but extinct clade flying reptiles of the order Pterosauria. For most of the Mesozoic, they existed: that is from those in the late Triassic to the end of the Cretaceous. Pterosaurs are the first vertebrate to have evolved powered flight.

Birds, are the modern organism analogous to the pterosaurs as Birds can fly and hunt insects and fish out of the ocean.