Argentavis Magnificens (Wingspan 7-7.6 m (23-25 ft))
– The Largest Bird Which Ever Flew
The bird world was turned upside down in 1979 when two well-known Argentinian paleontologists announced that they had unearthed the fossilized remains of a creature as large as a small glider. A bird which at rest could look a man in the eye and in flight cast a shadow as wide as four 2 m (6 ft) men lying end-to-end was almost too much to believe, for such a wingspan was far greater than any other represented in the fossil record.
History of teratorn species
The boffins went dashing for their slide rules and as a result, had to re-examine their theory as to size limitations in flight. Even now, it is admitted that our understanding of avian flight is still very limited, but there was a great deal of concrete evidence to deduce from this new genus and species of teratorn.
Assuming that it is reasonable to extrapolate directly from the size of other species, there is considerable confidence over Argentavis magnificens’ calculated standing height of 1.5 m (5 ft) and weight of 120 kg (265 lb), but it has been pointed out that the wingspan is just as likely to have been greater as smaller.
Drs. Eduardo Tonni and Rosendo Pascual’s research
Stretching 3.35 m (11 ft) from the tip of its bill to the tip of its tail, Argentavis magnificens dwarfed the previous record-holding teratorn – Incredibilis with its 5.2 m (17 ft) wingspan. Its remains had been found several years prior to 1979 by Drs. Eduardo Tonni and Rosendo Pascual beneath the dry, dusty plains of central Argentina. There were a number of pieces of skull, wing bones and leg bones, all from a single bird. This was found to be the oldest known teratorn, dating from the late Miocene period of 5—8 million years ago.
Argentavis Magnificens Facts and Information
There is no doubt that this great bird from a site 160 km (100 miles) west of Buenos Aires did fly as its discoverers found pieces of four different wing bones, and they are all of a size to be expected in a flying bird with such a wingspan. Living large birds that have lost the ability to fly, such as ostrich, rhea, and emu, have only rudimentary wings and wing bones which are very reduced — some even missing. Also, one Argentavis magnificens bone bears the marks where the secondary feathers were attached. The primary flight feathers might well have been as large as 18 cm (7 in) wide and 1.5 m (5 ft) long. It is assumed that this bird relied on soaring and only flapped its wings briefly when absolutely necessary because the physical limits of bone and muscle activity would have worked against sustained flapping. This is suggested by the similarity between the structure of the bones of teratorns and condors.
Argentavis magnificens Habitat
To get airborne, it is thought that all Aregntavis magnificens had to do was spread its wings into the wind, as condors of today often do. And there is considerable evidence to suggest that strong winds were a permanent feature of the Argentine climate in the late Miocene era. But with such large wings, taking off among and flying between trees and bushes would have been difficult so it is assumed that Argentavis magnificens would have been restricted to living in savannas or open grassland. Also walking in and around dense vegetation would have been avoided because of the increased danger of predators there.
What was their diet?
Though similar to condors in flight, teratorns differed in being much more agile on the ground. Indeed, this seems to have been essential for the way in which they fed. They did not swoop from the air on large, unsuspecting animals, but used their huge wings to hunt over vast areas in search of places where the generally low-density game of suitable size was concentrated — possibly around lake edges. There they stalked their prey until they were close enough to seize it with a quick thrust of the bill.
The skull of Argentavis magnificens was over 55 cm (22 in) long and 15 cm (6 in) wide and examination shows that it could have spread its mandibles wide enough to swallow prey larger than 15 cm (6 in) in diameter. Other animal remains from the same geological formation indicate that a hare-sized, rodent-like creature was particularly abundant at the time, but small armadillos may also have featured in the diet. Living forms of these animals are easily approached on foot, making them ideal prey for a stalking carnivore.
Furthermore, the long, narrow, hooked beak of Argentavis magnificens is indicative of a bird that grabs small animals and swallows them whole, and their feet were not of the type found in birds such as hawks, eagles, and owls which use their claws to catch and kill prey. It is thought prey was swallowed whole because the jawbones were too weak to kill large prey by biting or to tear large prey into pieces small enough for swallowing. And as they were probably hunters, their heads would have been feathered, as in almost all birds which are active predators.
The evolution of these gigantic birds seems to have proceeded in phase with the development of South American grasslands and semi-arid habitat, and the extinction of all the teratorns in North and South America may well have been linked to intolerable habitat alteration brought about by extreme dessication at the end of the Pleistocene era.
Few other known birds had wingspans over 5 m (16.25 ft). Among the most impressive was the Pelecaniforme Gigantornis eaglesomei from the Eocene deposits of Nigeria, which had long, narrow wings spanning some 6.1 m (20 ft), but such calculations are based merely on a single breastbone similar to that of an albatross.