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The teratorns were a group of very large birds of prey that lived in the Americas from the Oligocene to Pleistocene epochs. They are all extinct now. They include some of the largest known flying birds. So far, at least five species in four genera have been identified:

Teratornithidae are related to New World vultures (Cathartidae, syn. Vulturidae).

• Teratornis merriami. This is by far the best-known species. Over a hundred specimens have been found, mostly from La Brea tar pits. It stood about 75 cm (29.5 in) tall with estimated wingspan of perhaps 3.5 to 3.8 metres (11.5 to 12.5 ft), and weighed about 15 kg (33 lb); making it about a third bigger than living condors. It became extinct at the end of the Pleistocene, some 10,000 years ago.

• Argentavis magnificens. A partial skeleton of this enormous teratorn was found from La Pampa, Argentina. It is the largest flying bird known to have existed. It is the oldest known teratorn, dating to late Miocene, about 6 to 8 million years ago, and one of the very few teratorn finds in South America. Initial discovery included portions of the skull, incomplete humerus and several other wing bones. Even conservative estimates put its wingspan at 6 meters and up (some 20 ft), and it may have been as much as 8 metres (26 ft). The weight of the bird was estimated to have been around 80 kg (176 lb).

This group of huge birds lived at a time before mankind reached the Americas in any numbers. The land was more heavily forested than today, and so had herbivores more suited to forests than today. The finds in California suggest that similar conditions existed in much of California and North America west of the mountains. view more...