Teratornithidae

Teratornithidae
Temporal range: Miocene-Pleistocene
Teratornis
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Cathartiformes (disputed)
Family: Teratornithidae
L. H. Miller, 1909
Genera

Teratornis
Aiolornis
Argentavis
Cathartornis
Oscaravis

Teratorns (from the Greek Τερατορνις Teratornis, 'monster bird') are an extinct group of very large birds of prey that lived in North and South America from the Miocene to Pleistocene epochs. They include some of the largest known flying birds.

Taxonomy

Teratornithidae are related to New World vultures (Cathartidae, syn. Vulturidae).[1]

So far, at least five species in four genera have been identified:

Some cryptozoologists such as Ken Gerhard, and Mark A. Hall have expressed interest in Teratorns as a possible explanation of anecdotal sightings of very large birds in Texas and Illinois and popularly known as Thunderbirds.

Description and ecology

Despite their size, there is little doubt that even the largest teratorns could fly. Visible marks of the attachments of contour feathers can be seen on Argentavis wing bones. This defies some earlier theories that modern condors, swans, and bustards represent the size limit for flying birds. The wing loading of Argentavis was relatively low for its size, a bit more than a turkey's,[5] and if there were any significant wind present, the bird could probably get airborne merely by spreading its wings, just like modern albatrosses. South America during the Miocene probably featured strong and steady westerly winds, as the Andes were still forming and not yet very high.

T. merriami was small enough (relatively speaking) to take off with a simple jump and a few flaps. The fingerbones are mostly fused as in all birds, but the former index finger has partially evolved into a wide shelf at least in T. merriami, and as condors have a similar adaptation, probably in other species, too. Wing length estimates vary considerably but more likely than not were at the upper end of the range, because this bone structure bears the load of the massive primaries.

Traditionally, teratorns have been described as large scavengers, very much like oversized condors, owing to considerable similarity with condors. However, the long beaks and wide gapes of teratorns are more like the beaks of eagles and other actively predatory birds than those of vultures. Most likely teratorns swallowed their prey whole; Argentavis could technically swallow up to hare-sized animals in a single piece. Although they undoubtedly engaged in opportunistic scavenging, they seem to have been active predators most of the time.[5] Teratorns had relatively longer and stouter legs than Old World vultures; thus it seems possible that teratorns would stalk their prey on the ground, and take off only to fly to another feeding ground or their nests; especially Cathartornis seems well-adapted for such a lifestyle. Argentavis may have been an exception, as its sheer bulk would have made it a less effective hunter, but better adapted to taking over other predators' kills. As teratorns were not habitual scavengers, they most likely had completely feathered heads, unlike vultures.

As in other large birds, a clutch probably had only one or two eggs; the young would be cared for more than half a year, and take several years to reach maturity, probably up to a dozen in Argentavis.[6]

References

  1. Chatterjee, Sankar; Templin, R. Jack, Jr.; Campbell, Kenneth E. (July 24, 2007). "The aerodynamics of Argentavis, the world’s largest flying bird from the Miocene of Argentina". Proceedings of the National Academy of Sciences 104 (30): 12398–12403. doi:10.1073/pnas.0702040104. PMC 1906724. PMID 17609382. Retrieved 2014-05-16.
  2. 1 2 Miller, Loye H. (1909). "Teratornis, a new avian genus from Rancho La Brea". University of California Publications, Bulletin of the Department of Geology 5: 305–317.
  3. Campbell, Kenneth E. Jr. & Stenger, Allison T. (2002): A New Teratorn (Aves: Teratornithidae) from the Upper Pleistocene of Oregon, USA. pp. 1–11. in Zhou, Z. and F. Zhang. Proceedings of the 5th Symposium of the Society of Avian Paleontology and Evolution Beijing, 1–4 June 2000. China Science Press, Beijing.
  4. Howard, Hildegarde (1952). "The prehistoric avifauna of Smith Creek Cave, Nevada, with a description of a new gigantic raptor". Bull. S. Calif. Acad. Sci. 51: 50–54.
  5. 1 2 3 4 Campbell, Kenneth E. Jr. & Tonni, E. P. (1983). "Size and locomotion in teratorns" (PDF). Auk 100 (2): 390–403.
  6. Palmqvist, Paul & Vizcaíno, Sergio F. (2003). "Ecological and reproductive constraints of body size in the gigantic Argentavis magnificens (Aves, Theratornithidae) from the Miocene of Argentina" (PDF). Ameginiana 40 (3): 379–385.

Further reading

External links

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