Paleontologists have unearthed and examined a fossilized leg bone of a phorusrhacid bird that lived 12 million years ago in South America.
A model of Paraphysornis at the Natural History Museum Vienna. Image credit: Armin Reindl / CC BY-SA 4.0.
Terror birds are members of Phorusrhacidae, a family of large, carnivorous, flightless birds within the order Cariamiformes.
These extinct birds had a very large body mass, up to 70 kg, and were between 0.9-2 m (3-6.6 feet) in height.
They had slender bodies and unique locomotor adaptations for cursoriality.
Their immense beak and the mechanical adaptations of their skull suggest they were efficient predators.
They inhabited South America during the Cenozoic, but they are also known from the Plio-Pleistocene of North America and the Eocene of Africa.
Phorusrhacidae contains almost 20 species in 14 genera and 5 subfamilies (Brontornithinae, Mesembriornithinae, Patagornithinae, Phorusrhacinae, and Psilopterinae).
Their closest living relatives are believed to be seriemas, the sole living members of the family Cariamidae.
“Terror birds lived on the ground, had limbs adapted for running, and mostly ate other animals,” said Dr. Siobhán Cooke, a researcher at the Johns Hopkins University School of Medicine.
The end of a terror bird’s left tibiotarsus found in Tatacoa Desert, Colombia. Image credit: Degrange et al., doi: 10.1002/spp2.1601.
The fossilized leg bone of a terror bird was found in the 2000s in the fossil-rich Tatacoa Desert in Colombia.
The fossil dates back to the Miocene epoch around 12 million years ago, and is believed to be the northernmost evidence of a terror bird in South America thus far.
“The size of the bone also indicates that this terror bird may be the largest known member of the species identified to date, approximately 5-20% larger than known phorusrhacids,” Dr. Cooke said.
“Previously discovered fossils indicate that terror bird species ranged in size from 0.9 to 2.7 m (3-9 feet) tall.”
The fossil is also marked with probable teeth marks of Purussaurus, an extinct species of caiman that is thought to have been up to 9 m (30 feet) long.
“We suspect that the terror bird would have died as a result of its injuries given the size of crocodilians 12 million years ago,” Dr. Cooke said.
The terror bird also co-existed with primates, hoofed mammals, giant ground sloths and armadillo relatives, glyptodonts, that were the size of cars.
“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,” Dr. Cooke said.
The team’s paper will be published in the journal Papers in Palaeontology.
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Federico Javier Degrange et al. 2024. A gigantic new terror bird (Cariamiformes, Phorusrhacidae) from Middle Miocene tropical environments of La Venta in northern South America. Papers in Palaeontology 10 (6): e1601; doi: 10.1002/spp2.1601