The Rheidae is a still extant family, consisting of modern-day rheas and their extinct relatives. They are flightless and mainly herbivorous birds that live in South America. They are built for speed, being capable of running away from predators at high speed.
Distribution & Fossil evidence
The oldest known fossils of the Rheidae-family have been found in Brazil and date back to the Paleocene epoch, about 56 million years ago. Many other fossils have been found in Argentina, like Heterorhea and the large Hinasuri.
Nowadays, just two species are placed within this family, but they have several extinct relatives that date back all the way to the Paleocene epoch.