The place is called the “Giant's Causeway”, and this is no coincidence. Remains of native megafauna have already been found in a stream near the town of Canelones, just 45 minutes from Montevideo. Now, an unexpected fossil confirms that the name holds more truth than anyone could have imagined.
The bone fragment has led Uruguayan paleontologists to reconstruct the existence of a colossal vulture larger than the Andean condor—today the most impressive flying bird in the Americas—that soared through the skies of southern Pleistocene South America. According to the researchers, this bird could belong to a previously unknown lineage of South American catharthids.
The discovery was recently published in the journal Historical biologyoffers an unexpected look at the American Ice Age. It features a bird large enough to feed on glyptodonts and mastodons, as well as a powerful glider capable of traveling long distances in search of carrion.
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Two families of vultures
The study's lead authors, paleontologists Washington Jones and Andres Rinderknecht of the National Museum of Natural History, note that this “surprisingly large” bird bore similarities to the modern California condor.Gymnogypsum californica), belonging to the same lineage as the Andean condor (vulture vultures), and the slightly smaller Vulture King (Sarcorampus papa). They also describe certain morphological similarities to smaller vultures such as rufous and black-headed vultures.
By comparison, the general term “vulture” combines two types of birds with similar scavenger habits that are not directly related. On the one hand, the “Old World vultures” found in Africa and Asia belong to two different lineages: Hypaetins And Aegipinidaewhich are part Accipitridae family, as well as eagles and harriers. On the other hand, “New World vultures”, which include condors and American vultures, belong to the family cathartidsa group of birds unique to the Americas.
“This is the size of the largest condor, but the bone we found—the tarsometatarsus—has a very flattened shape, indicating that it is much more similar to native vultures, especially the rufous-headed vulture. That’s the surprise,” Jones says.
Think of it this way: This giant vulture would be slightly larger than the Andean condor, the world's largest flying bird, which can have a wingspan of about 10 feet (3 meters), and would be more than six times larger than the rufous vulture. Its very presence in the Pleistocene skies some 13,000 years ago would have been as impressive and terrifying as the giant mammals roaming the ground below it.
Comparison of vulture bones
Comparison of fossils with several tarsometatarsi of red-headed vultures.
(Image courtesy of Washington Jones)
The bone that allowed this giant bird to be identified is tarsometatarsusa structure that at first glance may seem unusual. In birds, several ankle and foot bones fuse into one elongated element, forming the so-called “bottom” of the leg, just above the toes. Unlike humans, who have a tibia, fibula, and then a foot, birds have three main segments: the femur, tibia, and tarsometatarsus.
The latter supports the toes and acts as a lever for walking, sitting or grasping prey, and its shape reveals key details about the animal's size and posture. Although the fragment, about 1.6 inches long, is broken, paleontologists were able to identify traces of tendon attachments and articular surfaces that may have connected to the toes, providing enough clues to reconstruct the size of the bird.
By comparison, the tarsus of the Californian or Andean condor is much more rounded; the Uruguayan fossil is similar in size, but noticeably more flattened and more similar to vultures of this genus. Catartesespecially the rufous vulture, although much larger.
However, Rinderknecht compared the fossil to the tarsus of California condors from the Smithsonian Institution's National Museum of Natural History and found that some also had flattened bones and some features similar to those of the Uruguayan specimen and the rufous vulture. This suggests two possibilities: the Uruguayan specimen represents a new large cathartid taxon related to the California condor, or a new large cathartid taxon related to Catartes.
“We speculate that our giant vulture may represent a new lineage, that is, a previously unknown evolutionary lineage among American vultures,” Jones explains.
Complex fossil region
Without additional bones, Jones and Rinderknecht were hesitant to give an official name, but they said they were convinced it represented a new form.
This caution also stems from the fact that in the Americas, bone fragments other than tarsometatarsi have not been matched to any known species, creating uncertainty about the true diversity of these vultures. In this context, Argentine paleontologist Marcos Cenizo, an expert on the evolution of birds, notes that although the specimens found in Uruguay are fragmentary, all evidence suggests that they are not related to the Andean condor.
He also warns that many of the species recorded from the South American Pleistocene may be overestimated because they are based on incomplete remains. According to Cenizo, the restraint shown by Uruguayan researchers in refusing to name the species reflects responsible scientific practice in light of the region's complex fossil record.
The disappearance of this giant vulture was likely closely related to the megafauna extinction at the end of the Pleistocene. The arrival of humans, whose hunting and landscape changes affected mastodons, giant sloths, glyptodonts and toxodonts, among others, also affected their scavengers.
Cenizo notes that, as in modern ecosystems of Africa and Asia, where the presence of megamammals coincides with a notable diversity of large vultures, it is reasonable to conclude that this giant South American vulture disappeared after its food sources disappeared.
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