The terror bird is the most complete skeleton ever discovered which represents a new species. Scientists have been able to reconstruct the shape of its inner ear.
Its ear structure offers hints about the hearing structure of the animal, which was probably lower than that of modern birds and suggests that they used low-pitched calls for interacting.
The find is reported in the Journal of Vertebrate Paleontology.
Palaeontologists from Argentina made the discovery in the cliffs of La Estafeta beach which is not very far from the popular tourist city of Mar del Plata.
Federico Degrange, one of the study’s authors, said dealing with the tide had presented a challenge.
“The sea can actually take the fossil and destroy it in the sea. It’s a nice place to work, but you have to be fast,” he told BBC News.
Phorusrhacids or terror birds were the dominant predators on the land of South America during their time which was followed by the extinction of dinosaurs some 65 million years ago.
These beasts stood up to 3 meters in height, with long legs and can waylay their prey in a single blow, before consuming its carcass.
“They evolved very unique forms, with huge skulls, huge beaks with hooks, and long hindlimbs,” said Dr Degrange, a terror bird specialist who works at the National University of Cordoba.
“They lost their ability to fly and they developed very unusual predatory capabilities that were not present in any comparable animals.”
The newly discovered species is called the Llallawavis scagliali, named after the senior author of the study Fernando Scaglia.
It was around 1.2 meters tall and weighed aroun 18 kilos, making it a medium-sized addition to the family of terror birds. But it still survived in the long period of ruling of that family 3.5 million years back.