Argentavis magnificens was among the largest flying birds ever to exist, quite possibly surpassed in wingspan only by Pelagornis sandersi, which was described in 2014. A. magnificens, sometimes called the Giant Teratorn, is an extinct species known from three sites in the Epecuén and Andalhualá Formations in central and northwestern Argentina dating to the Late Miocene (Huayquerian), where a good sample of fossils has been obtained.
The single known humerus (upper arm bone) specimen of Argentavis is somewhat damaged. Even so, it allows a fairly accurate estimate of its length in life. Argentavis’s humerus was only slightly shorter than an entire human arm. The species apparently had stout, strong legs and large feet which enabled it to walk with ease. The bill was large, rather slender, and had a hooked tip with a wide gape.
Argentavis wingspan estimates varied widely depending on the method used for scaling, i.e. regression analyses or comparisons with the California condor. At one time, wingspans have been published for the species up to 7.5 to 8 m (24 ft 7 in to 26 ft 3 in) but more recent estimates put the wingspan more likely in the range of 5.09 to 6.5 m (16 ft 8 in to 21 ft 4 in). Whether this span could have reached 7 m (23 ft 0 in) appears uncertain per modern authorities. At the time of description, Argentavis was the largest winged bird known to exist but is now known to have been exceeded by another extinct species, Pelagornis sandersi, was described in 2014 as having a typical wingspan of 7 to 7.4 m (23 ft 0 in to 24 ft 3 in). Argentavis had an estimated height when standing on the ground that was roughly equivalent to that of a person, at 1.5 to 1.8 m (4 ft 11 in to 5 ft 11 in), furthermore its total length (from bill tip to tail tip) was approximately 3.5 m (11 ft 6 in).
Prior published weights gave Argentavis a body mass of 80 kg (180 lb) but more refined techniques show a more typical mass would’ve likely been 70 to 72 kg (154 to 159 lb), although weights could’ve varied depending on conditions. Argentavis retains the title of the heaviest flying bird known still by a considerable margin, for example Pelagornis weighed no more than 22 to 40 kg (49 to 88 lb). For comparison, the living bird with the largest wingspan is the wandering albatross, averaging 3 m (9 ft 10 in) and spanning up to 3.7 m (12 ft 2 in). Since A. magnificens is known to have been a land bird, another good point of comparison is the Andean condor, the largest extant land bird going on average wing spread and weight, with a wingspan of up to 3.3 m (10 ft 10 in). This condor can weigh up to 15 kg (33 lb). New World vultures such as the condor are thought to be the closest living relations to Argentavis and other teratorns. Average weights are of course much less in both the albatross and condor than this teratorn, at approximately 8.5 kg (19 lb) and 11.3 kg (25 lb), respectively.