What defined the Phorusrhacids' role in the Cenozoic South American ecosystem?

Answer

Flightless apex predators succeeding non-avian dinosaurs

Terror birds were the undisputed, flightless apex predators of their time, stepping into the vacant role of top carnivore after the extinction of the non-avian dinosaurs.

What defined the Phorusrhacids' role in the Cenozoic South American ecosystem?
birdPredatorextinctfossilterror bird