After the dinosaurs became extinct, their bird descendants still managed to produce terrifying giants. Among these giant birds were a flightless group of carnivorous birds known as terror birds. One of the earliest version of these predators was Gastornis, which was seven feet tall and was the apex land predator fifty million years ago. One million years ago, the true terror birds ruled the savannah of prehistoric South America. These ten-foot-tall South America birds were known as Phorusrhacos and frequently competed the saber-toothed cat, Smilodon. However, the terror birds became extinct right before modern humans appeared. Their fate was sealed when they were outcompeted by specialized mammal predators. For my dinosaur book, I am thinking of giving the terror birds a comeback by introducing a reverse engineered version of them.