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Extinct family of birds From Wikipedia, the free encyclopedia
Teratornithidae is an extinct family of very large birds of prey that lived in North and South America from the Late Oligocene to Late Pleistocene. They include some of the largest known flying birds. Its members are known as teratorns.
| Teratornithidae | |
|---|---|
| |
| Teratornis merriami skeleton from the La Brea tar pits | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Accipitriformes |
| Family: | †Teratornithidae L. H. Miller 1909 |
| Genera | |
|
†Teratornis | |
Teratornithidae are related to New World vultures (Cathartidae, syn. Vulturidae).[1] So far, at least seven species in six genera have been identified:
Teratornithidae has only been included in a single phylogenetic analysis, published by Steven Emslie in 1988. The analysis was conducted using cranial characters of various taxa within the order Ciconiiformes, with a specific focus on Vulturidae (Cathartidae). This analysis included Teratornis merriami as a representative of Teratornithidae, and found the group to be just outside of Vulturidae.[8][9]
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 extant 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.
Studies on condor flight suggest that even the largest teratorns were capable of flight in normal conditions, as modern large soaring birds rarely flap their wings regardless of terrain.[10]
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 (much like extant caracaras), 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.
The skull features of teratorns still share a lot of crucial similarities with specialized scavenging raptors. Many old world vultures possess large bills similar to teratorns, and a longer bill is in fact an anatomic feature that points toward a scavenging rather than a predatory life style, as this allow them to probe deeper into large carcases - larger than those fed upon by active-hunting raptors. Other anatomical features, such as the relatively small and sideward facing orbits and the lower skull, are also consistent with a scavenging live style. More sideward facing eyes allow scavenging raptors to have a wider field of vision, which is advantageous in spotting carcases. In contrast, predatory raptors usually have proportionally larger and more forward facing orbits, as depth perception is more important for a predatory lifestyle.[11][12]
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 12 years in Argentavis.[13]
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