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Argentavis is an extinct genus of teratornithid known from three sites in the Epecuén and Andalhualá Formations in central and northwestern Argentina dating to the Late Miocene (Huayquerian). The type species, A. magnificens, is sometimes called the giant teratorn. Argentavis was among the largest flying birds to ever exist, holding the record for heaviest flying bird, although it was surpassed in wingspan after the 2014 description of Pelagornis sandersi, which is estimated to have possessed wings some 20% longer than those of Argentavis.<ref name=FWArgentavis>Argentavis at Fossilworks.org</ref><ref>Ancient American bird was glider. BBC, 2007-JUL-02. Retrieved 2008-JAN-14</ref>
Discovery and namingEdit
In the 1970s while on an expedition by the Museo de La Plata, paleontologists Rosendo Pascual and Eduardo Tonni unearthed a fragmentary skeleton consisting of a partial skull, right coracoid, left humerus, portions of the left ulna, left radius, and left metacarpals, and shafts of the right tibiotarsus and tarsometatarsus.<ref name=":1">Template:Cite journal</ref><ref name=":0">Template:Cite journal</ref> Later restudy of the specimen also found an incomplete ungual phalanx with the skeleton.<ref name=":0" /> These fossils had been exposed in brown-red silt and clay sediments from the Epecuén Formation in Salinas Grandes de Hidalgo in Atreucó, Argentina. These outcrops derive from the Huayquerian stage of the upper Miocene (9.0-6.8 mya). This specimen was deposited at the Museo de La Plata under catalogue number MLP 65-VII-29-49 and cast at the Los Angeles County Museum.<ref name=":1" />
These fossils were described by paleontologists Kenneth Campbell Jr. and Eduardo Tonni in 1980, who named the new genus and species Argentavis magnificens with MLP 65-VII-29-49 as the holotype specimen. The generic name Argentavis is derived from the Latin root argentum, “silver”, after the country of origin, and avis, “bird”, while the specific name magnificens, “magnificent”, refers to its size. In the description, Argentavis was classified as a member of Teratornithidae and was the first described from South America.<ref name=":1" /> Since Argentavis' description, Taubatornis was named and a multitude of specimens described from the continent.<ref>Template:Cite journal</ref><ref>Olson, S. L., & Alvarenga, H. (2002). A new genus of small teratorn from the Middle Tertiary of the Taubaté Basin, Brazil (Aves: Teratornithidae). Proceedings of the Biological Society of Washington.</ref> Later in 1995, Campbell described three additional Argentavis specimens that had been discovered in other sites in Argentina. One, an ungual phalanx, was unearthed in an Epecuén Formation outcrops around 60 km northeast of the holotype locality. Campbell assigned it to A. magnificens based on the development of grooves and tubercles on the bone,<ref name=":3">Campbell Jr, K. E. (1995). Additional specimens of the giant teratorn, Argentavis magnificens, from Argentina (Aves: Teratornithidae). Courier Forschungsinstitut Senckenberg, 181, 199-201.</ref> however due to the lack of overlap with the holotype and its robust morphology a 2011 article classified it as phorusrhacid.<ref name="Tambussi">Template:Cite journal</ref> Additionally, a fragmentary coracoid and the distal end of a tibiotarsus were collected from sediments of the Huayquerian-aged Andalhualá Formation in Valle de Santa María in Catamarca Province, northwest Argentina.<ref name=":3" />
DescriptionEdit
Argentavis was a large bird, with the length of the skull and humerus (upper arm bone) measuring Template:Cvt and Template:Cvt respectively.<ref name=":1"/> Although the humerus of Argentavis is somewhat damaged, it allows a fairly accurate estimate of its length in life. Argentavis had stout, strong legs and large feet which indicate decent terrestrial capabilities.<ref name=c&t1983/>
The initial description by Campbell and Tonni in 1980 tentatively estimated the wingspan of Argentavis between Template:Convert based on comparisons with Teratornis merriami.<ref name=":1"/> The 1983 study by the same authors estimated the wingspan of Argentavis by scaling up the dimensions of the California condor, with the highest estimate being Template:Convert and other estimates between Template:Convert.<ref name=c&t1983/> In their supplementary material of the 2024 paper, Gayford and colleagues considered the Template:Convert estimate to be an outlier.<ref>Template:Cite journal</ref> In 2010, Mayr and Rubilar-Rogers estimated the wing skeleton length of Argentavis and Pelagornis chilensis at Template:Convert and Template:Convert respectively, with P. chilensis having an estimated wingspan of Template:Convert, suggesting that Argentavis probably had a smaller wingspan unless it had much longer primary feathers.<ref>Template:Cite journal</ref> In his 2014 description of Pelagornis sandersi, Daniel Ksepka estimated the wingspan of P. sandersi at Template:Convert, exceeding that of Argentavis which he estimated at Template:Convert and Template:Convert based on regression analyses and comparisons with the California condor respectively.<ref name="Pelagornis">Template:Cite journal</ref><ref name=NG-Vergano>Template:Cite news</ref> For comparison, the living bird with the largest wingspan is the wandering albatross, reaching upwards of Template:Convert.<ref>Template:Cite journal</ref><ref>Template:Cite book</ref>
The initial description by Campbell and Tonni in 1980 tentatively estimated the body mass of Argentavis at Template:Convert,<ref name=":1"/> while the 1983 paper by the same authors estimated its body mass at approximately Template:Convert.<ref name=c&t1983/> Subsequent studies have suggested a lower body mass estimate between Template:Convert.<ref>Template:Cite journal</ref><ref name="Chatterjee07">Template:Cite journal</ref><ref name="Alexander">Template:Cite journal</ref> Argentavis still retains the title of the heaviest known flying bird by a considerable margin, with the aforementioned P. sandersi being estimated to have weighed no more than Template:Convert.<ref name="Pelagornis"/> Since A. magnificens is known to have lived in terrestrial environments, another good point of comparison is the Andean condor, the largest extant flighted land bird both in average wingspan and weight, with the former spanning up to Template:Convert with an average of around Template:Convert, and the latter reaching a maximum of up to Template:Convert. New World vultures such as the condor are thought to be the closest living relatives to Argentavis and other teratorns. Average weights are much lower in both the wandering albatross and Andean condor than in Argentavis, at approximately Template:Convert and Template:Convert, respectively.<ref name=CRC2>Template:Cite book</ref><ref name=Wood>Template:Cite book</ref>
As a rule of thumb, a wing loading of 25 kg/m2 is considered the limit for avian flight.<ref name=Meunier/> A number of estimates related to wing loading have been produced for Argentavis, most notably the wing area, estimated at Template:Convert, and the wing loading, estimated at 84.6 N/m2 (1.77 lb/ft2), or about 8.64 kg/m2.<ref name="Chatterjee07" /> The heaviest extant flying birds are known to weigh up to a maximum of Template:Convert (there are several contenders, among which are the European great bustard and the African kori bustard). An individual mute swan, which may have lost the power of flight due to extreme weight, was found to have weighed Template:Convert.<ref name=Wood/>
PaleobiologyEdit
Life historyEdit
Comparison with extant birds suggests Argentavis laid one or two eggs with a mass of around Template:Convert every two years. Climate considerations make it likely that the birds incubated during the winter, with members of a mated pair alternating between incubating and procuring food every few days. The young are thought to have been independent after some 16 months, but to not reach full maturity until they reached roughly twelve years of age. To maintain a viable population, no more than 2% of birds could have died each year. Because of its large size and ability to fly, Argentavis suffered hardly any predation, and mortality was mainly related to old age and disease in adults.<ref name=Palmqvist/>
FlightEdit
From the size and structure of its wings, it is inferred that A. magnificens flew mainly by soaring, using flapping flight only during short periods. This is further supported by skeletal evidence, which suggests that its breast muscles were not powerful enough to enable flapping of the wings for extended periods.<ref>Yong, Ed (2007-07-08) Argentavis, the largest flying bird, was a master glider. notexactlyrocketscience.wordpress.com</ref> Studies on condor flight indicate that Argentavis was fully capable of flight in normal conditions, as modern large soaring birds spend very little time flapping their wings regardless of environment.<ref>Template:Cite journal</ref>
Although its legs were strong enough to provide it with a running or jumping start, the wings were simply too long to flap effectively until the bird had gained some vertical distance, meaning that, especially for takeoff, Argentavis would have depended on the wind.<ref name="c&t1983" /> Argentavis may have used mountain slopes and headwinds to take off, and probably could manage to do so even from gently sloped terrain with little effort. It may have flown and lived much like the modern Andean condor, scanning large areas of land for carrion. It is probable that it utilised thermal currents to stay aloft, and it has been estimated that the minimal velocity for A. magnificens is about Template:Convert or Template:Convert.<ref name="Vizcaino" /> The climate of the Andean foothills in Argentina during the late Miocene was warmer and drier than today, which would have further aided the bird in staying aloft atop thermal updrafts.<ref name="Chatterjee07"/>
Predatory behaviorEdit
ArgentavisTemplate:' territories probably measured more than Template:Convert, which the birds screened for food, possibly utilizing a north–south flying pattern to avoid being slowed by adverse winds. This species seems less aerodynamically suited for predation than its relatives and probably preferred to scavenge for carrion. Argentavis may have used its wings and size to intimidate metatherian mammals and small phorusrhacids to take over their kills.<ref name="Tambussi"/><ref name="Palmqvist"/> Phorusrhacids were the largest land predators in Miocene South America, and probably the biggest threats that Argentavis faced, with the largest species that coexisted with Argentavis, Devincenzia, weighing up to Template:Convert.<ref>Template:Cite journal</ref> Torres Etchegorry & Degrange (2024) suggested that Argentavis was a scavenger or even a kleptoparasitic bird, living in open areas without much vegetation, based on its probable brain morphology inferred from endocast reconstruction.<ref>Template:Cite journal</ref>
ReferencesEdit
Further readingEdit
- Template:Cite journal
- Wellnhofer, Peter (1996): The Illustrated Encyclopedia of Pterosaurs. Barnes and Noble Books, New York. Template:ISBN
External linksEdit
- Argentavis information Website about the Argentavis magnificens
- BBC News: Ancient American bird was glider – BBC News article
- How the dinosaur bird took to the skies – Daily Telegraph article
- Secret of flight for world's largest bird revealed – COSMOS magazine article
- Argentavis, the largest flying bird, was a master glider – Article from the blog Not Exactly Rocket Science