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

Phorusrhacos were also known as terror birds. 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.

Phorusrhacos Scientific Name

The common name of Phorusrhacos is terror bird. 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. Florentino Ameghino first described it in 1887, amended its name to Phororhacos in 1889, and in 1891, he recognized it as a bird.

Phorusrhacos is in the class Aves (birds) and in the order Cariamiformes, an order of mostly flightless birds that have existed for over 60 million years. It is in the family Phorusrhacidae, also known as phorusrhacids or terror birds.

The closest living relatives of terror birds are the modern Seriema birds of South America. They are members of the same order, Cariamiformes.

Phorusrhacos Appearance

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. Some birds were only 2 to 3 feet high. It weighed about as much as a male ostrich, but without the small head and beak. It has stubby, flightless wings, a long neck, a very large head with a huge, hooked beak which resembled that of a modern eagle. It also had very strong legs with three toes on each feet and sharp claws, plus a tuft of feathers on top of its head.

Phorusrhacos Behavior

Beak size was sexually differentiated. Hence, males with larger beaks were more attractive to females during the mating season.

It is thought that Phorusrhacos first grabbed its prey in its claws. It then used its beak to smash it against the ground or puncture the head to cause major brain damage and kill it. Smashing it against the ground broke its bones to make them easier to swallow as well as make them easier to tear off pieces with claws and beak.

As an apex predator for its time and location, it was rivalled only by saber-toothed cats like Smilodon. 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 Population

Phorusrhacos were an important part of the megafauna, or giant beasts in Pleistocene South America. As an apex predator, they kept prey animal populations down. They were in fact the largest predators during the “Age of Mammals” in South America. Like modern ostriches, emus, and cassowaries, and the extinct moas, they were flightless.

Phorusrhacos Reproduction & Life Cycle

Not much information is known about Phorusrhacos’ 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 ate any animals that were smaller than them. This meant small and medium-sized prey, especially those that were too small to grasp with their wings.

Habitat – When and Where It Lived

The Miocene Epoch was between 7,000,000 and 26,000,000 years ago. Phorusrhacos lived during the early to middle Miocene Period, or between 20,000,000 to 1,000,000 years ago. They lived in what is now modern-day Argentina, which was part of Patagonia, the southern area of South America encompassing Argentina and Chile. Their habitat was the woodland and grassland plains of Argentina.

Phorusrhacos Threats And Predators

Phorusrhacos was an apex predator that was rivaled only by other apex predators in its ecosystem. Males were also rivaled by other males, and when they fought each other, they would use their claws and beaks.

Discoveries and Fossils – Where It was Found

There were several locations where remains were found in the Santa Cruz Formation as well as the Monte Leon Formation, both in the Santa Cruz Province of Argentina. It was a piece of mandible Florentino Ameghino found in early 1887, which was also when he described it as an edentate mammal and named it Phorusrhacos longissimus.

Extinction – When Did It Die Out?

Terror bird populations started decreasing and eventually went extinct after larger apex predators migrated from North America to South America. These new predators had their own unique hunting behaviors and strategies.

Similar Animals to The Phorusrhacos

Another terror bird in the same family of Phorusrhacidae was Kelenken guillermoi, which lived in Florida and Texas in the early Pliocene to early Pleistocene epochs and the early to middle Miocene in Florida. Kelenken had a skull that was over 28 inches long. Another terror bird, Titanis walleri, was in the genus Titanus. It lived in North America during the early Pliocene to early Pleistocene epochs.

The closest relatives of terror birds are the modern Seriema birds of South America.

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