Evolutionary biologists have examined a fossil of a long-extinct giant carnivorous bird, which may be the largest ever discovered of its species, shedding light on animal life in northern South America millions of years ago.
Researchers, including an evolutionary biologist from Johns Hopkins University, have looked into a fossil of an extinct gigantic meat-eating bird, which might be the largest known of its type. Their study offers new insights into the fauna of northern South America from millions of years ago.
The study, published on November 4 in Palaeontology, centers on the leg bone of the terror bird. It was spearheaded by Federico J. Degrange, a specialist in terror birds, and included Siobhán Cooke, Ph.D., an associate professor at the Johns Hopkins University School of Medicine. This bone, discovered in the fossil-rich Tatacoa Desert in Colombia, is currently considered the northernmost evidence of the bird’s presence in South America.
The dimensions of the bone suggest that this terror bird could be the largest known member of the species, measuring about 5% to 20% larger than previously identified Phorusrhacids, as stated by Cooke. Previous fossil findings indicate that terror birds varied in height from 3 to 9 feet.
“Terror birds were terrestrial creatures, built for running, and primarily consumed other animals,” Cooke describes.
The leg bone was unearthed by Cesar Augusto Perdomo, curator of the Museo La Tormenta, nearly two decades ago, but its identification as a terror bird only occurred in 2023. In January 2024, researchers created a 3D virtual representation of the specimen with a portable scanner from Johns Hopkins Medicine, facilitating further study.
This fossil, specifically the end of a left tibiotarsus (a lower leg bone in birds likened to the human tibia), is estimated to date back to the Miocene epoch, around 12 million years ago. The bone features distinct pits unique to the legs of all Phorusrhacids and shows possible tooth marks from an extinct caiman, known as Purussaurus, which could have reached lengths of up to 30 feet, as indicated by Cooke.
“We believe the terror bird may have succumbed to injuries inflicted by the size of crocodilians existing 12 million years ago,” she notes.
Most terror bird fossils have been found in the southern regions of South America, particularly in Argentina and Uruguay.
The discovery of a Phorusrhacid fossil as far north as Colombia implies it played a significant role in the predatory wildlife of the area. This fossil contributes essential understanding of the ecosystem present in the region 12 million years ago. Today a desert, scientists theorize the area was once characterized by winding rivers. This imposing bird coexisted with primates, hoofed mammals, giant ground sloths, and car-sized glyptodonts, relatives of armadillos. The modern-day seriema, a long-legged bird indigenous to South America reaching heights of up to 3 feet, is considered a contemporary relative of Phorusrhacid.
“This ecosystem was distinct from what we observe today or in other global regions before South and North America were joined,” explains Cooke.
The fossil, thought to be the first of its kind from this site, suggests that this species was relatively rare among the fauna 12 million years ago, according to Cooke.
“There may be fossils in existing collections that haven’t been identified as terror birds since their bones can be less distinctive than the leg bone we found,” she remarks.
For Cooke, this discovery allows her to envision an environment that no longer exists.
“It would have been an incredible experience to wander through and see all of these now-extinct creatures,” she reflects.
Alongside Cooke and Perdomo, the study includes contributions from Federico Javier Degrange of Centro de Investigaciones en Ciencias de la Tierra; Luis G. Ortiz-Pabon from Universidad de Los Andes, Carrera, Bogotá, Colombia, and Universidad Nacional de Colombia, Carrera, Bogotá; Jonathan Pelegrin from Universidad del Valle, Colombia, and Universidad Santiago de Cali, Colombia; Rodolfo Salas-Gismondi from Universidad Nacional Mayor de San Marcos, Avenida Arenales, Perú; and Andrés Link from Universidad de Los Andes, Carrera Bogotá, Colombia.
