This “Terror Bird” Dinosaur Ran Faster Than Any Human

Written by Krishna Maxwell
Updated: January 23, 2023
© Michael Rosskothen/
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Key Points

  • While these flightless birds are called “terror birds” because of their size and speed, they ate mostly insects and rodents.
  • Phorusrhacos averaged 8.2 feet from the bottom to the top of its head. Some grew by as much as 10 feet. The back was about 4 feet and 7 inches, while its skull alone could be as long as 60 cm. It weighed around 290 pounds.
  • The Phorusrhacos lived in the grasslands and woodlands of South America.

Phorusrhacos (FOE-roos-RAY-cuss), or rag bearer in Greek, is an extinct genus of giant flightless terror birds that lived in Argentina during the Miocene epoch. These birds were the top killers before humans and saber-toothed cats came to the Americas. While they could not fly, the Phorusrhacos could grow as large as 10 feet and had a huge beak and large, sharp claws.

At the time of its existence, Phorusrhacos was a top land predator in South America. It has gone through a lot of names, including Darwinornis, Titanornis, Stereornis, and Liornis. The name Phorusrhacos stuck, but it was more popularly known as “Terror Bird.”

Scientific NamePhorusrhacos Ameghino
Name meaningRag Bearer
Named byFlorentino Ameghino
HabitatPlains of South America/Argentina, Santa Cruz province
Historical EpochMiddle Miocene (12 million years ago) / Ice Age / Pleistocene (up to 1.8 million years ago)
ClassificationChordata, Aves, Cariamae, Phorusrhacidae, Phorusrhacinae
Size and weightAbout eight feet tall and 300 pounds (approx. 8.2 feet tall and 290 pounds) / skull up to 65 centimeters long
SpeedAround 50 km/h or 31 mph, slower than an ostrich
Distinguishing CharacteristicsLarge head, large beak, claws on wings
Fossil representationMany known specimens

Description and Size

The fossils of the Phorusrhacos were first discovered in 1887. Since then, it has gone by several names. However, the name Phorusrhacos, which came from a fossil hunter, stuck. This fossil hunter used that name because it assumed that he was dealing with a megafauna mammal because of the size of its bones. This is why “ornis,” the Greek term for bird, was missing from the species’ name. The reason why it was named “rag bearer” is still a mystery today.

Though Phorusrhacos is its official name, it is referred to as Terror Bird since it is easier to pronounce. It was rightfully described because, judging from the fossils, Phorusrhacos was enormous with big and powerful jaws. It also had clawed wings. Males had bigger beaks that made them more attractive to females during mating season.

According to experts, Phorusrhacos averaged 8.2 feet from the bottom to the top of its head. Some grew by as much as 10 feet. The back was about 4 feet and 7 inches, while its skull alone could be as long as 60 cm. It weighed around 290 pounds.

The general build of the Phorusrhacos was similar to flightless birds, such as penguins, ducks, weka, ostrich, kiwi, kakapo, and takahe. It had sharp, hook-tipped claws on its reduced wings. Thanks to its natural ability to catch animals, the Phorusrhacos also had huge claws on its toes.

Terror Bird Phorusrhacos Computer generated 3D illustration
Terror birds were 8 feet tall and weighed 300 pounds.

©Michael Rosskothen/


Like many predatory birds, the Phorusrhacos had a hook-tipped beak. It was the primary weapon for killing their prey. There are two existing theories on how the Terror Bird used its beak. The first theory is it used the beak to catch the prey and portion the meat, while the second is that it utilized the hooked curve as a pickax since it attacked the prey from above.

What Did Phorusrhacos Eat?

Although it is called a Terror Bird, Phorusrhacos only hunted small insects and medium mammals. Its relatives in the Brontornis species were left to hunt for bigger animals. Since this animal had weak and small wings, these features did not help at all in catching prey. The Phorusrhacos’ hook-tipped beak and clawed wings helped it catch prey. Also, it had long and strong legs to run after relatively fast mammals.

The Phorusrhacos used its claws and beak to bang its prey to the ground. Then, it used its claws to tear off the flesh and access the meat. This made the Phorusrhacos purely carnivorous, though experts also believed that this species also ate carcass.

Most experts believe that the Phorusrhacos hunted by hiding behind bushes and thin trees. The tree trunk hid them, allowing them to pounce on their prey. They hunted more efficiently by surprise.

While these birds mostly ate insects and small animals, they certainly could have killed a human. Their closest modern counterpart has been known to kill people by striking forward with their powerful claws. With their weight and speed, they are able to disembowel a human or other animal.


The Phorusrhacos lived in the grasslands and woodlands of South America. The Phorusrhacos country is the present Patagonia region that covers the vast southernmost tip of South America. The area straddles Argentina and Chile, with the Andes Mountains in the middle.

Steppes, deserts, and grasslands characterize present Argentina. On the other hand, Chile has glacial fjords and rainforests. Researchers believed that Phorusrhacos stayed near thin outcroppings of shrubs and trees because they blended well with the tree trunks.

Threats and Predators

It is hard to imagine anything preying on Phorusrhacos. It was not called Terror Bird for nothing since it could easily defend itself using its beak and claws. It is not clear if the Phorusrhacos was a hunter in the truest sense of the word. Many believe that it was smart enough to hide behind tree trunks and wait to pounce on its prey.

It used a couple of killing methods. The Phorusrhacos used its sharp beak to pick its prey and throw it against the ground. This attack killed the small prey and broke its bones so they could easily be swallowed. Breaking the prey’s bones also made it easier for the Phorusrhacos to use their claws to tear off animals too large to swallow.

The Phorusrhacos might have also used its beak to make precision strikes on the parts of the prey’s body. The hooked beak would have helped to knock out the prey by striking it on the skull. So strong was the Phorusrhacos strike that it pierced the skull and caused damage to the brain.

Discoveries and Fossils

Florentino Ameghino first described the Phorusrhacos in 1887. The basis was a fragment of a jaw. Most of the skulls were not preserved, though Florentino Ameghino had enough time to illustrate and write about them. Only a brief description was written about the skull remains of the Phorusrhacos.

Since then, the skull remains of the Phorusrhacos have been scarce. Not much is known about the cranial anatomy of the Terror Bird until new cranial material referable to Phorusrhacinae Phorusrhacos longissimus was found. These materials, comprising a skull roof, partial mandible, and rostrum, were discovered at two sites in the Santa Cruz province of southern Argentina.

The vertebra was found at a different locality than the associated cranium and mandible. The site where the cranium and mandible were found was less than 50 kilometers east of the Chilean border. This only proved that the natural habitat of the Phorusrhacos used to be near the Andes Mountains.


Data suggests that Phorusrhacos became extinct because of the presence of new predators. While the Phorusrhacos was considered a terror for mammals, it preyed only on insects and medium mammals. The arrival of new competition in its natural habitat led many experts to believe that this species became extinct because they were no longer dominant.

Similar Animals to Phorusrhacos

The Phorusrhacos is compared to many other animals that resemble it in size and characteristics. Here are some of the most popular comparisons made over the years:

  • Titanis: Another “terror bird” that is comparable in size to the Phorusrhacos. It went extinct during the Pleistocene epoch, with many experts classifying it as a species of Phorusrhacos.
  • Kelenken: The biggest predatory bird. It also had the enormous skull of all birds. Its height was over three meters.
  • Penguin: These flightless birds are often compared to Phorusrhacos. All 18 species of penguins cannot fly, and they are built better for swimming and diving. They are popular because of the way they walk — they waddle — and mostly live in Antarctica.
  • Steamer Duck: These aggressive flightless birds can be found in South America. They cross waterways by thrashing their wings, which earned them their names. These birds battle each other over territories.
  • Weka: A native of New Zealand, these birds are also skilled swimmers. They are now decreasing in number, so most environmentalists are concerned about a possible extinction.
  • Ostrich: Called the king of birds, the ostrich is the largest living bird as it can grow up to nine feet tall and weigh more than 300 pounds. It has powerful legs to run at speeds up to 45 miles per hour.
  • Kiwi: To some, kiwis look like brown chickens. However, a strange characteristic of kiwi is the nostrils on the tip of their bills.

Up Next…

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About the Author

Krishna is a lifelong animal owner and advocate. She owns and operates a small farm in upstate New York which she shares with three dogs, four donkeys, one mule, and a cat. She holds a Bachelors in Agricultural Technology and has extensive experience in animal health and welfare. When not working with her own animals and tending her farm, Krishna is helping other animal owners with behavior or management issues and teaching neighboring farmers about Regenerative Agriculture practices.

FAQs (Frequently Asked Questions) 

When did Phorusrhacos live?

The Phorusrhacos lived in South America up to the Pleistocene epoch, which was 1.8 million years ago.

How big was the Phorusrhacos?

The Terror Bird measures an average of eight feet tall. It weighs between 280 to 300 pounds.

What did the Phorusrhacos feed on?

The Phorusrhacos was a carnivore. It fed on small insects and middle-size mammals that it hunted. However, Phorusrhacos was not known as an apex predator nor a scavenger. Instead, it hunted out of need, but it could also feed on animal carcasses.

What were the distinguishing features of Phorusrhacos?

The most distinguishing features of the Phorusrhacos were its hook-tipped beaks and clawed wings. Without these, the Phorusrhacos would look like any other ordinary flightless bird.

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