A 12-million-year-old fossil of a prehistoric "terror bird" discovered in South America might represent the largest known member of its kind found to date, a study has reported.
A lower leg bone of the "gigantic" bird was found by a museum curator in Colombia's fossil-rich Tatacoa desert around 20 years ago, but it was not recognized as a terror bird until 2023.
This year, researchers created a three-dimensional virtual model of the specimen using a portable scanner, enabling them to analyze the fossil further for a study.
"We are talking about a species that was larger than 2.5 meters [8.2 feet] and weighed more than 150 kilograms [330 pounds]," study author Federico Javier Degrange with the Center for Research in Earth Sciences in Argentina told Newsweek.
Phorusrhacids-commonly known as "terror birds"-belong to an extinct family of medium to extremely large-sized meat-eating birds that were apex predators during a large portion of the Cenozoic Era-around 66 million years ago until today.
These birds, which have been found primarily in southern South America, had slender bodies and unique locomotor adaptations for running, with the largest species being flightless.
Their "immense" beak and the mechanical adaptations of their skull suggest that they were efficient predators.
"Terror birds lived on the ground, had limbs adapted for running, and mostly ate other animals," study author Siobhán Cooke, an associate professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine, said in a press release.
In the latest paper, published in the journal Papers in Palaeontology, the authors presented the fossil as the first record of a large terror bird from the Middle Miocene (around 16 million to 11.6 million years ago) fossil deposits in central Colombia.
While the specimen consists only of a fragmentary portion of a lower leg bone known as the left tibiotarsus, its size led the researchers to suggest that it may correspond to one of the largest terror birds known to have ever existed, possibly weighing around 340 pounds-although this is a very rough estimate given the fragmentary nature of the remains. The fossil is also thought to be the northernmost evidence of such birds found in South America to date.
The researchers estimate that the animal was approximately 5 to 20 percent larger than other known terror birds, which are thought to have ranged in size from 3- to 9-feet tall based on previously discovered fossils.
The specimens could well represent a new species within the phorusrhacid group. But limited material has prevented the researchers from unequivocally assigning the fossil to a new species or genus.
"Although it is quite possible that it is a new species we do not have certainty," Degrange told Newsweek.
Intriguingly, the fossil also shows evidence of teeth marks that are judged to have probably belonged to an extinct caiman, or crocodilian, species-purussaurus-that is thought to have grown up to 30 feet in length.
"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 said.
Reference
Degrange, F. J., Cooke, S .B., Ortiz-Pabon, L. G., Pelegrin, J. S., Perdomo, C. A., Salas-Gismondi, R., Link, A. (2024). A gigantic new terror bird (Cariamiformes, Phorusrhacidae) from Middle Miocene tropical environments of La Venta in northern South America. Papers in Palaeontology. https://onlinelibrary.wiley.com/doi/epdf/10.1002/spp2.1601
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