Huge fossil of terror birds offers new insight into nature in South America 12 million years ago

Researchers, including an evolutionary biologist from Johns Hopkins University, report that they have analyzed a fossil of an extinct giant carnivorous bird – which they say could be the largest known relative of its kind – providing new information about animal life in the northern South America, millions of years ago.

The proof lies in the terror bird’s leg bone, described in a new paper published on November 4 Paleontology. The research was led by Federico J. Degrange, a specialist in terror birds, and included Siobhan Cookeassociate professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine. The bone, found in Colombia’s fossil-rich Tatacoa Desert at the northern tip of South America, is believed to be the northernmost evidence of the bird in South America to date.

The size of the bone also indicates that this terror bird may be the largest known member of the species identified to date, about 5% to 20% larger than known. Phorusrhacidssays Cooke. Previously discovered fossils indicate that terror bird species ranged in size from 10 to 12 feet tall.

“Terror birds lived on the ground, had limbs adapted for running and usually ate other animals,” says Cooke.

The bird’s leg bone was found almost twenty years ago by Cesar Augusto Perdomo, curator of the Museo La Tormenta, but was only recognized as a terror bird in 2023. In January 2024, researchers created a three-dimensional virtual model of the specimen using a portable scanner from Johns Hopkins Medicine, allowing them to analyze it further.

The fossil, the end of a left tibiotarsus, a lower leg bone in birds equivalent to that of a human tibia or tibia, dates to the Miocene, about 12 million years ago. The bone, with deep pits unique to everyone’s legs Phorusrhacidsis also marked with likely tooth marks of an extinct caiman –Purussaurus– a species thought to have been as long as 30 feet, Cooke says.

“We suspect that the terror bird would have died as a result of its injuries, given the size of crocodilians 12 million years ago,” she says.

Most terror bird fossils have been identified in the southern part of South America, including Argentina and Uruguay.

Scientists believe that the Tatacoa Desert was once an environment full of winding rivers. This gigantic bird lived among primates, hoofed mammals, giant ground sloths and armadillo relatives, glyptodonts, which were the size of cars.

The discovery of Phorusrhacid fossils as far north as Colombia suggests it was an important part of the region’s predatory wildlife. Importantly, this fossil will help researchers better understand the animals that lived in the region 12 million years ago. Scientists believe this region is now a desert and was once an environment full of winding rivers. This gigantic bird lived among primates, hoofed mammals, giant ground sloths and armadillo relatives, glyptodonts, which were the size of cars. Today it is believed that the Seriema, a long-legged bird native to South America that can grow up to a meter in height, is a modern relative of Forusrhacid.

“It’s a different kind of ecosystem than we see today or in other parts of the world in a period before South and North America were connected,” Cooke says.

The fossil is believed to be the first of its kind at the site and indicates that the species would have been relatively uncommon among animals there 12 million years ago, Cooke says.

“It is possible that there are fossils in existing collections that have not yet been recognized as terror birds because the bones are less diagnostic than the lower leg bone we found,” she says.

For Cooke, the find helps her imagine an environment that can no longer be found in nature.

“It would have been a fascinating place to walk around and see all these now extinct animals,” she says.

In addition to Cooke and Perdomo, the study’s authors also include first author Federico Javier Degrange of Centro de Investigaciones and Ciencias de la Tierra; Luis G. Ortiz-Pabon of 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 of Universidad Nacional Mayor de San Marcos, Avenida Arenales, Perú; and Andrés Link from Universidad de Los Andes, Carrera Bogotá, Colombia.