Researchers studying the leg bone of a 'terror bird' say it could be the largest member of its family ever documented.
The massive, meat-eating bird was a fearsome predator that roamed northern South America millions of years ago. The fossil sheds new light on ancient wildlife in the region, say the team, who described the discovery in a recent paper published in Palaeontology.
The study was led by terror bird expert Federico J. Degrange.
Epic discovery
The fossil was found in Colombia’s Tatacoa Desert, an area rich in prehistoric life, and marks the northernmost record of this species in South America to date.
The size of this fossilised bone indicates the bird was likely 5%–20% larger than any other known Phorusrhacid, a group of giant, flightless predatory birds.
Earlier fossils have shown that these birds varied in height, with some towering as tall as nine feet. “Terror birds lived on the ground, had limbs adapted for running, and mostly ate other animals,” says co-author Siobhán Cooke, associate professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine.
The leg bone, discovered nearly 20 years ago by Cesar Augusto Perdomo, curator of Colombia’s Museo La Tormenta, was only identified as belonging to a terror bird in 2023. A few months later, researchers created a three-dimensional virtual model of the specimen using a portable scanner.
Bone deductions
The bone – specifically the end of the left tibiotarsus (the bird equivalent of a shin bone) – dates back around 12 million years to the Miocene epoch.
The fossil carries teeth marks probably left by an extinct giant caiman known as Purussaurus, which reached lengths of up to 30 feet. “We suspect that the terror bird would have died as a result of its injuries given the size of crocodilians 12 million years ago,” Cooke explains.
Most terror bird fossils have previously been found in southern South America, especially in Argentina and Uruguay, but this northern discovery suggests they played a prominent role in Colombia’s ancient ecosystem.
The finding allows researchers to better picture the wildlife that populated the area – once dominated by winding rivers – 12 million years ago.
The giant bird coexisted with primates, hoofed mammals, massive ground sloths and glyptodonts – enormous, armoured relatives of modern armadillos.
Today, the seriema, a tall-legged bird native to South America, is considered a close modern relative of Phorusrhacids.
“It’s a different kind of ecosystem than we see today or in other parts of the world during a period before South and North America were connected,” Cooke says.
The fossil also offers insight into the rarity of these birds in this northern habitat. Cooke believes there could be more fossils out there in museum collections that are yet to be identified as terror birds.
Reflecting on the discovery, Cooke imagines a landscape vastly different from today’s world. “It would have been a fascinating place to walk around and see all of these now extinct animals,” she says.
The research team included Federico Javier Degrange from the Centro de Investigaciones en Ciencias de la Tierra, alongside co-authors from Universidad de Los Andes, Universidad Nacional de Colombia, Universidad del Valle, Universidad Santiago de Cali, Universidad Nacional Mayor de San Marcos, and Museo La Tormenta.
Find out more about the study.
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