Scientists discovered a new species of extinct "terror bird" that once lived in South America. 

The bird, dubbed Llallawavis scagliai ("Scaglia's Magnificent Bird") provides insight in the diversity of these types of birds and how they interacted with their environment.

The new fossil is the most complete terror bird skeleton ever discovered, with over 90 percent of it still intact, the Society of Vertebrate Paleontology reported. The findings also revealed details of the bird's anatomy including the voice box, trachea, and bones for focusing the eye. Evidence of the auditory region of the skull allowed the scientists to learn about how the ancient animal heard the world around it.

"The mean hearing estimated for this terror bird was below the average for living birds," said Federico "Dino" Degrange, lead author of the study from the Centro de Investigaciones en Ciencias de la Tierra (CICTERRA), CONICET and the Universidad Nacional de Córdoba, Argentina. "This seems to indicate that Llallawavis may have had a narrow, low vocalization frequency range, presumably used for intraspecific acoustic communication or prey detection."

This is the first time structures that reveal hearing sensitivity have been reconstructed for a terror bird, and the breakthrough could explain the evolution of the entire bird group. Terror birds were carnivorous flightless birds that could be as tall as 10 feet. They were believed to be the top predators in South America during the Cenozoic Age. This new species was only four feet tall and lived in Argentina about 3.5 million years ago.

"The discovery of this species reveals that terror birds were more diverse in the Pliocene than previously thought. It will allow us to review the hypothesis about the decline and extinction of this fascinating group of birds," Degrange said.

The findings were published in a recent edition of the Journal of Vertebrate Paleontology.