Researchers, including Federico J. Degrange and Siobhán Cooke, Ph.D., from Johns Hopkins University, recently analyzed a fossil of an extinct giant, meat-eating bird commonly known as a “terror bird.” This fossil could represent the largest member of its kind discovered so far, offering fresh insight into the diversity of animal life that inhabited northern South America millions of years ago. The fossil study was published on November 4 in the journal Palaeontology.
The evidence rests in a partial leg bone, specifically the lower left tibiotarsus, found nearly two decades ago in the Tatacoa Desert of Colombia. This arid region, known for its wealth of fossils, now adds terror birds to its list of prehistoric inhabitants, marking this discovery as the northernmost evidence of terror birds on the continent. Federico J. Degrange, a noted terror bird specialist, led the study, and Siobhán Cooke of Johns Hopkins University contributed significant insights into the fossil’s implications for evolutionary biology.
Analysis of the fossil revealed that this particular bird may have been up to 20% larger than previously discovered Phorusrhacids, Cooke notes, making it potentially the largest known member of the terror bird lineage. Fossils of these birds, which are known for their intimidating size and carnivorous habits, generally indicate a height range of 3 to 9 feet. Terror birds, flightless and equipped with long, powerful legs, were built for running and primarily preyed on other animals, making them some of the dominant predators of their time.
The bird’s leg bone was originally discovered by Cesar Augusto Perdomo, the curator of Colombia’s Museo La Tormenta. Despite being found almost 20 years ago, the bone was only recently identified as belonging to a terror bird in 2023. In January 2024, researchers from Johns Hopkins Medicine used a portable scanner to create a detailed 3D model of the bone, which helped them to better examine its structure and unique features.
The fossil dates back to the Miocene epoch, around 12 million years ago. Distinctive characteristics, such as deep pits found on the leg bone, are consistent with the anatomy of Phorusrhacids. The bone also bears marks that may have been inflicted by an extinct caiman known as Purussaurus, a colossal crocodilian believed to have reached up to 30 feet in length. The presence of these marks suggests the bird could have been fatally injured by an encounter with this ancient predator, Cooke explains.
Until now, terror bird fossils had primarily been unearthed in southern South America, particularly in regions like Argentina and Uruguay. This northern discovery suggests that these birds were more widespread across South America than previously thought. The presence of a Phorusrhacid fossil this far north indicates that these apex predators played a crucial role in the ecosystems of prehistoric northern South America.
Today, the Tatacoa Desert is an arid landscape, but scientists believe that during the Miocene, it was lush with meandering rivers and hosted a variety of unique wildlife. Terror birds would have roamed alongside an array of now-extinct creatures, including large ground sloths, giant glyptodonts, primates, and hoofed mammals. Modern descendants of terror birds may include the seriema, a South American bird that stands up to three feet tall.
Siobhán Cooke describes the ancient ecosystem as fundamentally different from today’s environment, with a mixture of species that evolved in isolation, as the land bridge connecting South and North America had not yet formed. This unique ecosystem included predators and prey unlike those in other parts of the world at the time.
The terror bird bone from the Tatacoa Desert is considered a rare find, suggesting that these birds may have been relatively uncommon in the region. Cooke notes that other specimens may exist in museum collections, misidentified due to the challenges of classifying such remains without distinctive features like the unique lower leg bone. This discovery opens up possibilities for identifying more terror bird fossils in existing collections.
For Cooke, this finding ignites her curiosity about the long-lost environments of the Miocene epoch. Imagining the ecosystem populated by terror birds, enormous crocodilians, and other extinct species, she reflects on how these discoveries allow scientists to piece together ancient worlds no longer visible in nature.
Alongside Cooke and Perdomo, other study authors include Federico Javier Degrange of the Centro de Investigaciones en Ciencias de la Tierra, Luis G. Ortiz-Pabon of Universidad de Los Andes and Universidad Nacional de Colombia, Jonathan Pelegrin of Universidad del Valle and Universidad Santiago de Cali, Rodolfo Salas-Gismondi of Universidad Nacional Mayor de San Marcos in Peru, and Andrés Link of Universidad de Los Andes. Together, their work contributes to a growing understanding of the prehistoric life that once thrived in the diverse and dynamic landscapes of ancient South America.