Teratornithidae is an extinct family of very large birds of prey that lived in North and South America from the Late Oligocene to Late Pleistocene. They include some of the largest known flying birds. Its members are known as teratorns.
Taxonomy Teratornithidae are related to New World vultures (Cathartidae, syn. Vulturidae). The fact that both of the oldest taxa in the group, Taubatornis and Argentavis, originate from South America suggests that the group as a whole also evolved here, only migrating to North America in the latter part of the Cenozoic. So far, seven species in six genera have been identified:
Teratornis Teratornis merriami. This is by far the best-known species. Over a hundred specimens have been found, mostly from the La Brea Tar Pits. It stood about 75 centimetres (30 in) tall with an estimated wingspan of 3.5 to 3.8 metres (11 to 12 ft), and weighed about 15 kilograms (33 lb); making it about a third bigger than extant condors. It became extinct at the end of 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 4 metres (13 ft). 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 has 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 23 kilograms (51 lb) and a wingspan of about 5.5 metres (18 ft) 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 the Huayquerian, about 9 to 6.8 million years ago, and it is one of the few teratorn finds in South America. The initial discovery included portions of the skull, an incomplete humerus and several other wing bones. Even conservative estimates put its wingspan at 6 metres (20 ft) and up, and it may have been as much as 8 metres (26 ft). The weight of the bird was estimated to have been around 80 kilograms (180 lb). Oscaravis olsoni was described from the Pleistocene of Cuba, but its affinities are not completely resolved; it might not be a teratorn at all. There are also undescribed fossils from southwestern Ecuador. Taubatornis campbelli is the earliest known teratorn species, from the Late Oligocene or Early Miocene of the Tremembé Formation, Taubaté Basin, Brazil.
Classification Teratornithidae has only been included in a single phylogenetic analysis, published by Steven Emslie in 1988. The analysis was conducted using cranial characters of various taxa within the order Ciconiiformes, with a specific focus on Vulturidae (Cathartidae). This analysis included Teratornis merriami as a representative of Teratornithidae, and found the group to be just outside of Vulturidae.
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