Terror birds survived millions of years longer than previously thought
A 25,000-year-old fossilized “drumstick” is writing a new chapter for these flightless birds that terrorized the post-dinosaur world.
Terror birds that once dominated South America’s savannas with giant, hooked beaks and fleet feet may have survived much longer than previously believed.
Researchers long thought the largest of these birds went extinct in South America at the end of the Pliocene Epoch, some 2.58 million years ago, and that smaller ones died out shortly after. But now, paleontologists at a museum in Brazil have found evidence of a tiny terror bird that lived 25,000 years ago.
The finding is the most recent directly dated terror bird fossil discovered so far, adding to mounting evidence that the last survivors of this group hung on until the peak of the last Ice Age.
“A new chapter has opened,” says Victor Hugo Machado, an independent paleontologist working with the Natural Sciences Museum at the Pontifical Catholic University of Minas Gerais in Brazil, and an author of the recent study. “This shows that smaller species from the family survived a long time.”
Machado made the discovery after re-examining a fossilized “drumstick” in the museum’s collections and realizing it belonged to a small terror bird. He and his colleagues named the new species Eschatornis aterradora, or the “last terror bird.”
Extreme apex predators
For millions of years, terror birds terrorized present-day South America. They came onto the scene 43 million years ago, but at first were relatively modest in size. Over the eons, they grew gigantic, with some reaching 10 feet tall and more than 700 pounds, and preying upon deer-like herbivores.
The giant birds were mostly flightless. Instead, they likely used their speed to chase prey on land. They wielded their heavy, hooked beaks like hatchets to smash into their victims, and their massive toe claws to stomp or kick their prey.
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“They dominated as apex predators,” Machado says. Different-sized species preyed on animals up and down the food chain, turning a post-dinosaur world into something that resembled the Cretaceous.
Terror birds were “the last gasp of that theropod dinosaur in birds,” says Tom LaBarge, a doctoral candidate in paleontology at Indiana University who studies terror birds but was not involved in the new study. Its features, he adds, “all point to a quite extreme predator.”
Drumstick of terror
The new discovery came from a reclassification of a bone found in the 1980s by Machado’s coauthor Cástor Cartelle, who works at the museum. Cartelle conducted excavations at the Tocas dos Ossos Cave in Bahia, Brazil, and found numerous fossils, including many mammalian fossils.
Among these remains was a single left tibiotarsus bone—basically the drumstick. In 2008, researchers described the bone as belonging to a vulture species, after which it was forgotten. Then in 2024, Machado began to reexamine the bone and realized right away that while it “superficially resembled those of vultures,” he says it had features more consistent with terror birds.
The new species, E. aterradora, was relatively less terrifying than its ancestors, weighing only an estimated 13 pounds. Using radiocarbon dating, the team discovered the bone was about 25,000 years old. They published their findings in March in the journal Papers in Palaeontology.
The authors note that the finding is not the first time paleontologists have found a recent terror bird bone. Other researchers have discovered terror bird remains in Uruguay that suggest they, too, lasted into the Late Pleistocene—including one dating to 96,000 years ago and another perhaps as recently as 17,500 years ago. The dating of the more recent Uruguay specimen, which is from a different terror genus than the one from Brazil, was not done on the bird’s fossilized bone, however. Instead, the dating comes from an analysis of a tooth from an extinct elephant relative, called a Stegomastodon, discovered in the same deposit.
LaBarge says he is excited by Machado’s discovery, calling the data “very sound.” When combined with the Uruguay specimens, the dating shows the persistence and resilience of these tiny terror birds. “They were not doing too terribly even at this most recent time,” says LaBarge.
Terror bird demise
The recent dating of the terror birds could mean that they were once in contact with humans. The earliest dates of human colonization of the Americas are still contested, but excavations at the Santa Elina rock shelter in southern Brazil, for example, have revealed tools and pendants that could date back as far as 25,000 years.
Previously, most researchers believed that terror birds went extinct due to the connection of North and South America via the Isthmus of Panama about 3 million years ago. This new land connection enabled a massive exchange of species between the previously separate continents.
“That really led to a continent-wide restructuring of the ecosystem,” LaBarge says.
For the most part, the large South American predators were on the losing end, getting outcompeted by more generalist species like saber-toothed cats and wolves from North America. At least one giant terror bird species—Titanis walleri—made inroads into the north, reaching as far as Texas and Florida before disappearing about 1.8 million years ago. But the only ones that seem to have survived into the Late Pleistocene were the smaller ones that didn’t compete directly with the North American predators, Machado says.
Instead of being outcompeted, he says that other factors, such as climate change and the loss of the large arboreal savannas, put an end to the prehistoric lands they terrorized for so long.
