Descendants of The Terror Birds

Illustration of a Terror Bird, Titanis walleri (image from Wikimedia Commons)

12 January 2025

Today we live among the descendants of the Terror Birds. Who were they? And who are they now?

Terror Birds (Phorusrhacids) were a genus of large, flightless, carnivorous birds that thrived in South America from 43 million to 100,000 years ago. Wikipedia describes them as “among the largest apex predators in South America during the Cenozoic era.”

As you can see from this diagram the largest of them could easily have eaten a human and, because Homo sapiens evolved around 300,000 years ago, we were on Earth before they went extinct. We would have been in danger but we were in Africa, separated by an ocean from these terrifying ancestors of modern birds.

Height comparison of four Terror Birds (illustration from Wikimedia Commons, includes accuracy note)

DNA studies in 2024 refined the phylogenetic supertree of birds placing Terror Birds as ancestors in the clade Australaves, the group that evolved in South America and Australia. Click on the image below to see a larger version of the diagram.

Phylogenetic supertree by Stiller, J., Feng, S., Chowdhury, AA. *et al.* Complexity of avian evolution revealed by family-level genomes. *Nature* 629, 851–860 (2024). https://doi.org/10.1038/s41586-024-07323-1

Because the diagram has hundreds of tiny details I’ve hand-drawn the Terror Bird section starting with their nearest living relative, the seriema. Notice who else is descended from the Terror Birds!

Australaves descended from the Terror Birds, drawn by Kate St. John, derived fromphylogenetic supertree by Stiller, J., Feng, S., Chowdhury, AA. *et al.* Complexity of avian evolution revealed by family-level genomes. *Nature* 629, 851–860 (2024). https://doi.org/10.1038/s41586-024-07323-1

Let’s take a photographic journey through the tree.

First come the seriemas, who stand alone without other relatives. These South American birds have a lifestyle is similar to the secretarybird of Africa though they are not related. Here a red-legged seriema (Cariama cristata) kills a snake.