Teratornis incredibilis, Merriam's Teratorn, was a huge North American bird, with a wingspan of around 3.5 to 3.8 meters (11 to 12 feet), standing an estimated 75 cm tall and weighing about 15 kg; thus, it was somewhat larger than the extant Andean Condor and nearly two times as heavy as the Californian Condor. A closely related species, the Incredible Teratorn, 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, Aiornis, nowadays.

This species 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 but one Early Pleistocene partial skeleton from the Leisey Shell Pit near Charlotte Harbor, Florida (which may represent a different species) are of Late Pleistocene, with the youngest remains dating from the Pleistocene-Holocene boundary.

Merriam's Teratorn probably lived in a manner similar to modern-day condors, although its larger bill suggests that it was a more active predator. Smaller prey, up to the size of a large rabbit or small cat, would probably be swallowed more or less whole, while carrion would have been fed on in a manner similar to condors or vultures. Indeed, the large number of finds in the La Brea Tar Pits are probably of animals who were attracted by megafauna that became stuck in the viscous asphalt trying to drink from pools of water that gathered on the surface and died, with the teratorns subsequently falling victim to the sticky deposits too. Merriam's Teratorn probably played an important role in opening up the body cavities of carcasses for smaller birds like eagles and ravens which are also known to have frequented the locality, as mammalian predators, being unable to fly, could hardly reach most carcasses without getting mired in the asphalt themselves.

The species probably became extinct as the depletion of megafauna decrerased prey availability. Despite being a better hunter than the Californian Condor, it still was inferior as a predator to smaller birds of prey, and the higher population density and wider range of the condor probably ensured that it survived while Merriam's teratorn didn't. Additionally, the changes in ecosystems brought about by the end of the last glaciation and the increasing human influence (such as burning off woodland to provide more habitat for prairie species) decreased availability of food and habitat even further.

Merriams Teratorn and humans

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T. merriami is the largest species of flying bird that without any doubt was encountered alive by humans. The initial reaction was probably one of awe, but as bones found in Amerindian middens show, the bird was not considered sacred enough not to be hunted. On the other hand, the species was probably large and possibly predatory enough to consider human infants food, albeit certainly not on a regular basis. After the species became extinct, its memory apparently persisted to form a major foundation, if not the foundation, for the Thunderbird myths. Somewhat simplifyingly, when the largest flying bird ever seen alive by humans was no more, it was transformed into a supernatural creature. It is of course impossible to prove nowadays that this species served as the factual basis underlying the Thunderbird of legend, but it is certain that the enormous Merriam's Teratorns, soaring in the thermal updrafts of an approaching thunderstorm, scouring the land for food far and wide, were a sight that was frequently enough encountered by the first humans to settle North America.

References

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• Miller, Love H. (1909): Teratornis, a new avian genus from Rancho La Brea. Univ. California Publ., Bull. Dept. Geol. 5: 305-317.

genera of birds | Late Quaternary prehistoric birds | Pleistocene birds | teratornithidae

teratornis