Teratornithidae is an extinct family of very large birds of prey that lived in North and South America from the Late Oligocene to the Late Pleistocene. They include some of the largest known flying birds. Taxonomy Teratornithidae are related to New World vultures (Cathartidae, syn. Vulturidae). So far, at least seven species in six genera have been identified: Teratornis Teratornis merriami. This is by far the best-known species. Over 100 specimens have been found, mostly from the La Brea Tar Pits. It stood about tall with an estimated wingspan of perhaps , and weighed about ; making it about a third bigger than extant condors. It became extinct at the end of the Pleistocene, some 10,000 years ago. Teratornis woodburnensis. The first species to be found north of the La Brea Tar Pits, this partial specimen was discovered at Legion Park, Woodburn, Oregon. It is known from a humerus, parts of the cranium, beak, sternum, and vertebrae which indicate an estimated wingspan of over . The find dates to the Late Pleistocene, between 11,000 and 12,000 years ago, in a stratum which is filled with the bones of mastodons, sloths, and condors, and bears evidence of human habitation. Aiolornis incredibilis, previously known as Teratornis incredibilis. This species is fairly poorly known; finds from Nevada and California include several wing bones and part of the beak. They show remarkable similarity with merriami but are uniformly about 40% larger: this would translate to a mass of up to and a wingspan of about for incredibilis. The finds are dated from the Pliocene to the Late Pleistocene, which is a considerable chronological spread, and thus it is uncertain whether they actually represent the same species. Cathartornis gracilis. This species is known only from a couple of leg bones found from La Brea Ranch. Compared to T. merriami, remains are slightly shorter and clearly more slender, indicating a more gracile build. Argentavis magnificens. A partial skeleton of this enormous teratorn was found from La Pampa, Argentina. It is one of the largest flying birds known to have existed, only likely exceeded by measurement of wingspan by Pelagornis sandersi, discovered in 1983. Fossil remains of this species have been dated to Late Miocene, about 6 to 8 million years ago, and one of the few teratorn finds in South America. Initial discovery included portions of the skull, incomplete humerus and several other wing bones. Even