Teratorns, (from the greek Teratornis “Monster Bird”) were massive Pleistocene birds. Merriam’s Teratorn lived in Northern America. Over 100 of this species have been found at the Rancho La Brea Tar Pits. While these birds have a skeletal structure that is similar to a condor, research indicates that these birds were active predators that stalked their prey from the air – and did not solely survive on carrion. It’s wingspan was 11-12 feet in length, and it’s body weighed about twice as much as the modern day California Condor. The legs were similar to an Andean Condor’s, but more stout, and the feet were able to hold prey for tear off pieces, but did not have the forceful grip of birds of prey. It’s lifestyle was similar to that of a condor, but it’s beak does suggest it ate some small prey whole (such as rabbits) and also hunted aquatic prey in a manner similar to an Osprey. It fed on carrion in a way similar to a vulture, and it’s believed that so many of these specimens have been found in the tar pits because they were attracted to dead and dying animals already trapped, and then became trapped in the tar as well.
A closely related genus, the Aiolornis, was about 40% larger and lived at an earlier time in Argentina; it was formerly known as Teratornis incredibilis, but is distinct enough to be placed in its own genus.
All skeletal remains but one early Pleistocene exception of a 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.