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Extinct Teratorn (Family Teratornithidae) Fact Sheet: Taxonomy & History

Extinct Teratorn (Teratornis merriami, Aiolornis incredibilis, Cathartornis gracilis, Argentavis magnificens) Family Teratornithidae

How Do We Know This?

Like living animals, fossil remains of once-living animals are
classified and grouped according to their relationships to each other and to their ancestors.
Some fossils yield DNA which helps scientists determine these animals' similarity to living animals.

Taxonomy and Nomenclature

  • Teratorns originally placed in family of Vultures (Cathartidae) because of hooked beak and condor-like skeleton of Teratornis merriami (Miller 1909)
  • In 1981 and 1983 Campbell suggested T. merriami was not a vulture or a scavenger, but an active predator capable of hunting and walking with features common to both storks and vultures as well as unique features of neither group.
  • In 1999, Campbell revised the taxonomy of T. incredibilis and placed it in a new genus, Ailornis.
  • In 2007, paleontologists said Argentavis and other teratorns are related to storks (Ciconiidae) and New World vultures (Vulturidae) and belonged in the order Ciconiiformes with other long-legged wading/walking/soaring birds. (Chatterjee et al 2007)
    • Much current discussion about which modern and fossil birds belong in this order, considering recent genetic studies.

Evolutionary History

  • An ancestral teratorn (Argentavis magnificens) known from Miocene rocks (about 6 million years old) in Argentina (Campbell & Tonni 1980)
    • Teratorns probably originated in South America.
  • Ailornis incredibilis (known previously as Teratornis incredibilis) fossils found from 3-4 million years ago to about 20,000 years ago; this long time span suggests Ailornis is actually more than one species. (Campbell et al 1999)
  • Cathartornis gracilis is known from only two leg bones at Late Pleistocene La Brea deposits; it may not be distinct from T. merriami. (Campbell & Tonni 1983)
  • Oldest North American records for T. merriami are from the Anza-Borrego Desert in California from Pliocene and Pleistocene rocks. (Howard 1963, 1972). Also over 100 specimens from Late Pleistocene California's Rancho La Brea asphalt deposits.
  • No members of the teratorn family survived Pleistocene times; they have been extinct for at least 10,000 years.


Kingdom: Animalia

Phylum: Chordata

Class: Aves

Order: Accipitirformes - includes hawks, eagles, vultures (or Ciconiiformes - includes storks, herons); taxonomy at this level uncertain

Family: Teratornithidae (extinct family of prehistoric birds)

Genus: Teratornis

Species: Teratornis merriami (Miller, 1909) - Merriam's Teratorn (extinct)

Genus: Aiolornis

Species: Aiolornis incredibilis (Howard, 1952; new combination by Campbell) - Incredible Teratorn (extinct)

Genus: Cathartornis

Species: Cathartornis gracilis (Miller, 1910) - Slender Teratorn (extinct)

Genus: Argentavis

Species: Argentavis magnificens (Campbell & Toni, 1980) - Magnificent Argentine Teratorn (extinct)

Page Citations

Campbell et al. (1999)
Campbell & Tonni (1980, 1983)
Chatterjee et al. (2007)
Howard (1963, 1972)
Miller (1909)

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