Teratornis

Teratornis was a huge North American teratorn bird of prey. It is the best-known of the teratorns. A large number of fossil and subfossil bones, representing more than 100 individuals, have been found in locations in California, southern Nevada, Arizona, and Florida, though most are from the Californian La Brea Tar Pits. All remains except one Early Pleistocene partial skeleton from the Leisey Shell Pit near Charlotte Harbor, Florida (which may represent a different species or a subspecies) date from the Late Pleistocene, with the youngest remains dating from the Pleistocene-Holocene boundary.

Taxonomy

 * Teratornis merriami.[1] 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 extant condors. It became extinct at the end of the Pleistocene, some 10 000 years ago.
 * Teratornis woodburnensis.[2] 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 meters (14 ft). The find dates to the late Pleistocene, between 11,000 and 12,000 years ago, in a strata which is filled with the bones of Mastodon, Sloth and Condors, and bears evidence of human habitation.

Another form, "Teratornis" olsoni, was described from the Pleistocene of Cuba, but its affinities are not completely resolved; it might not be a teratorn, but has also been placed in its own genus, Oscaravis. There are also undescribed fossils from southwestern Ecuador, but apart from these forms, teratorns were restricted to North America.

Description
Teratornis merriami had a wingspan of around 3.5 to 3.8 m (11 to 12 ft) and a wing area of 17.5 square meters, standing an estimated 75 cm (30 in) tall. It was somewhat larger than the extant Andean Condor and weighing about 15 kg (33 lb), was nearly double the weight of an average California Condor. A closely related genus, Aiolornis, was about 40% larger and lived at an earlier time; it was formerly known as Teratornis incredibilis, but is distinct enough to be placed in its own genus.

The finger bones are fused as in all modern birds; however, part of the index finger forms a shelf which aided in bearing the load of long and stout primaries, which enabled the bird to utilize strong upcurrents. The legs were similar to an Andean Condor's, but stouter, and the feet could hold prey items for tearing off pieces, but could not exert a very forceful grip such as in birds of prey. Its wing loading was not much larger than a Californian Condor's, and Merriam's Teratorn should have been able to take off by simply jumping and beating its wings under most circumstances.[4] Indeed, it seems to have been better adapted for that than for utilizing a short run into the wind from an elevated location as condors do, as its legs are proportionally smaller and its stride less than in condors.