Phorusrhacos longissimus

Last updated: September 27, 2022
Verified by: AZ Animals Staff
© Michael Rosskothen/

It's a genus of terror birds


Phorusrhacos Scientific Classification



Scientific Name
Phorusrhacos longissimus

Read our Complete Guide to Classification of Animals.

Phorusrhacos Conservation Status

Phorusrhacos Locations

Phorusrhacos Locations

Phorusrhacos Facts

Main Prey
Small and medium-sized animals
Saber-toothed cats
  • Solitary
Phorusrhacid, aves
It's a genus of terror birds

Phorusrhacos Physical Characteristics

Skin Type
Top Speed
31 mph
300 lbs
7ft 10in-10ft 2in

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Phorusrhacos is an ancient, extinct genus of flightless, giant carnivorous birds.

Phorusrhacos was also known as a terror bird. They were an apex predator in South America during the Miocene period, second only to saber-toothed cats like Smilodon. The terror birds lived in what is now modern-day Argentina, which was part of Patagonia, the southern area of South America encompassing Argentina and Chile.

5 Phorusrhacos Fun Facts

  • Their beaks were large and strongly curved, forming a hook shape seen in other carnivorous birds.
  • They were one of the biggest carnivorous birds to ever exist.
  • They lived during the Middle Miocene period, which was 12 million years ago.
  • Their closest relatives are the modern Seriema birds of South America.
  • They went extinct when larger apex predators migrated from North to South America.

Description & Size

Phorusrhacos is a genus of giant terror birds that lived in South America during the Miocene epoch. The type species of this genus is the Phorusrhacos longissimus. Phorusrhacos comes from the Greek word phoros meaning “bearer” and rhakos meaning “rag” or “wrinkle,” referring to the bird’s jaw surface being wrinkled. Its name in Latin means “very long,” referring to the lower jaw.

Like the other terror birds from the same period, this bird had a large head with a massive beak that was shaped like a hook at the top, similar to modern-day birds of prey such as the eagle. The lower jaw of this large beak was smaller than the upper jaw. Like present-day ostriches, they could not fly due to its small wing that could not support its weight in the air. The small wings did had sharp claws at the end. This bird probably used it as a weapon in hunting prey and fending off other predators. 

Phorusrhacos’s massive body was supported on long skinny legs that allowed them to run at a very high speed. They stood at about 7.8 feet to 8.9 feet tall and weighed nearly 300 pounds, nearly the same weight as an average male ostrich today. Of course, their large head and sharp beaks gave them a more intimidating appearance. The skull was nearly 25 inches in length on a very long neck. Their long, skinny legs ended in sharp talons. There were three toes on each foot, and each one had sharp talons that could dig into prey. 

Beak size was sexually differentiated. Hence, males with larger beaks were more attractive to females during the mating season. It could hear a wide range of sound frequencies and had excellent vision, but a poor sense of smell. A well-developed cerebral cortex meant it was not limited to pre-defined thought patterns and could adapt to different situations.

Phorusrhacos Reproduction & Life Cycle

Not much information is known about Phorusrhacos‘s reproduction and life cycle. However, fossil findings show that in all stages of development, the terror birds kept their same proportions of head, beak, body, and leg size. Their eggs would have been as large as ostrich eggs, if not larger.

Diet – What Did Phorusrhacos Eat?

Phorusrhacos and other terror birds were carnivorous. Their strong downward curving beaks were capable of ripping into the flesh of their pretty. Standing at over 8 ft in height, the Phorusrhacos was undoubtedly one of the largest predators in the niche it occupied. 

Scientists are not exactly sure of the animals that it fed on. But their diet might have included any of the smaller prey animals that lived at the time, which must have included small rodents and mammals.

Initially, scientists thought Phorusrhacos killed prey by catching it in its beak and shaking it from side to side. However, new studies of the bones of the beak show that the beak was strong enough to impact a significant downward pecking force that could have killed prey. 

Habitat – When and Where It Lived

Phorusrhacos was one of the most dominant land predators in South America during the Miocene Epoch. Their fossils have been discovered in an area known as Patagonia in the Southern region of South America, which is now in present-day Argentina and Chile. Scientists believe that this region comprised woodland and grassland habitats during this period.  

Phorusrhacos Threats And Predators

Until the Great American Biotic Interchange occurred about 3 million years ago due to the appearance of a land bridge that linked South and North America, Phorusrhacos was the most dominant predator in the niche it occupied. However, with the appearance of the land bridge, large predators like the Saber-Toothed tiger were able to migrate into South America. This upset Phorusrhacos’s dominance in its habitat. 

Considering the bird’s size, it is unlikely that these newcomer predators hunted Phorusrhacos. However, competition for similar prey would have put pressure on the Phorusrhacos population. 

Discoveries and Fossils – Where It was Found

Paleontologists have found several fossils of Phorusrhacos from several localities in the Santa Cruz Province of Argentina. The first fossil of this terror bird was discovered in early 1887 by Florentino Ameghino. This bone was a piece of mandible bone. 

Based on the initial description, scientists thought it belonged to an edentate mammal and named it Phorusrhacos longissimus. Subsequent discoveries a few years later confirmed that the jawbone belonged to a giant bird and not a mammal as it was initially believed. 

Extinction – When Did It Die Out?

Phorusrhacos terror birds most likely disappeared about 2.5 million years ago. Scientists often link the disappearance of this genus of terror birds to the appearance of a land bridge known as the Isthmus of Panama about 2.7 million years ago. This led to the Great American Biotic Interchange. During this time, several animal species from the North American continent crossed over into South America. The Phorusrhacos population declined after this exchange. They could not keep up with the increased competition for food that followed the arrival of new predators into the South American region. 

Similar Animals to The Phorusrhacos

Similar animals to Phorusrhacos include: 

  • Titanis: This is an extinct genus of giant terror birds that lived in North America around the same time as Phorusrhacos. The Titanis was slightly smaller than its South American counterpart. 
  • Argentavis magnificens: Argentavis magnificens lived on the South American continent about 6 million years ago. Although not a terror bird, Argentavis was quite large as well. It is considered the largest flying bird to have ever existed. 
  • Sparassodonts: Sparassodonts most likely shared the same niche with the terror birds in South America. They are carnivorous mammals that are close relatives to marsupials. 
  • Kelenken: The Kelenken was the largest of the terror birds. It lived in South America about 15 million years ago. 

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Phorusrhacos FAQs (Frequently Asked Questions) 

When was the Phorusrhacos alive?

It was alive during the early to middle Miocene period.

How big was Phorusrhacos?

It was about as large as an ostrich, if not larger.

Where did it live?

It lived in the woodland and grassland plains of Argentina.

What did it eat?

It ate small to medium-sized prey that was smaller than it.

How fast could it run?

Its long legs allowed it to run up to 31 miles per hour.

What's the difference between Phorusrhacos and Seriema?

Both are in the same order of Cariamiformes, and that’s where their similarities end. Seriema birds are also related to falcons, parrots, and passerine birds, and have omnivorous diets consisting of both animal and plant matter.

What type of covering does Phorusrhacos have?

It had skin covered with feathers, with a small tuft of feathers on top of its head.

What were its predators?

Saber-toothed cats were its predators.

How many babies did it have?

It is unknown how many eggs the females had.

What is a fun fact about it?

It had a well-developed prefrontal cortex.

What was its lifespan?

It is unknown what its lifespan was.

Why did it go extinct?

It went extinct because of other apex predators that migrated from North to South America during the Miocene period.

How big was Phorusrhacos?

Phorusrhacos had a skull measuring about 65 inches long, a height of 7 feet 10 inches to 10 feet 2 inches tall, and about 300 pounds in weight.

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