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Extinct Teratorn (Family Teratornithidae) Fact Sheet, 2009   Tags: bird, extinct, fact sheet, fossil, san diego zoo, sdzg, teratorn  

Extinct Teratorn (Teratornis merriami, Aiolornis incredibilis, Cathartornis gracilis, Argentavis magnificens) Family Teratornithidae
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Extinct Teratorn (Family Teratornithidae) Fact Sheet, 2009

Extinct Teratorn 

Image credit: © San Diego Zoo Global. All rights reserved.

TaxonomyPhysical Characteristics

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)

Estimated Body Weight
Teratornis merriami: 13.7 kg (30.2 lb); slightly heavier than living California Condor
Ailornis incredibilis: 23 kg (50 lb)
Argentavis magnificens: 70 kg (154 lb); 7 times heavier than California Condor

Estimated Wingspan
Teratornis merriami: 3.5-4 m (11.5-13.1 ft)
Ailornis incredibilis: 5.0-5.5 m (16.4-18 ft)
Argentavis magnificens: 6-8 m (19.7-26.3 ft)

Distribution & StatusBehavior & Ecology
Argentavis magnificens
: known from central and northwestern Argentina
Teratornis merriami: known from California, plus Florida, New Mexico, and Mexico
Cathartornis gracilis: known only from Rancho La Brea, California
Ailornis incredibilis: found in southern California and Nevada

Argentavis: dependent on geography that created updrift thermals (e.g., mountains and associated grasslands)
Teratornis: less open habitats, such as coastal shrub and woodlands in California

No members of the teratorn family survived Pleistocene times; they have been extinct for at least 10,000 years.

Walking and soaring flight.

Interspecies Interactions
Likely interactions with other daytime raptors and scavengers.

Carnivorous; also scavenged on carrion.
Armadillos, rodent-like mammals, possums, and capybara may have been food for Argentavis magnificens.
Lizards, snakes, small and medium-sized mammals, and birds may have been food for Teratornis merriami.

Not well understood; possibly other raptors.

Reproduction & DevelopmentSpecies Highlights

May have had breeding cycles similar to similar-sized modern day raptors. Reproduction characterized small clutchs (1-2 eggs per clutch), 2-3 year breeding cycles, and long nestling periods.

Largest teratorns probably had a long life span.

Feature Facts

  • Large, soaring, predatory and scavenging (extinct) birds
  • Probably hunted during the day, using thermals for flight
  • Teratornis merriami able to move well on the ground
  • Argentavis magnificens could have swallowed hare-sized prey in one gulp.

About This Fact Sheet

© 2009 San Diego Zoo Global

How to cite: Extinct Teratorn (Family Teratornithidae) Fact Sheet, 2009. c2009. San Diego (CA): San Diego Zoo Global; [accessed YYYY Mmm dd].
(note: replace YYYY Mmm dd with date accessed, e.g., 2015 Sep 10)

Disclaimer: Although San Diego Zoo Global makes every attempt to provide accurate information, some of the facts provided may become outdated or replaced by new research findings. Questions and comments may be addressed to

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