According to researchers, they have discovered 90%-complete ‘terror bird’ skeleton on an Argentinean beach. The skeleton suggests that these big-beaked predators had good low-frequency hearing and deep voices.

The researchers said that it is most full skeleton that ever found for one of these menacing beasts and also represents a new species. The shape of its inner ear has been reconstructed by researchers. After this, the researchers were able to know about the animal's hearing.

This also provides hints about the animal's hearing that was likely lower than that of modern birds. It has been suggested that they used low-pitched calls to communicate. The discovery was made by Argentinian paleontologists in the cliffs of La Estafeta beach.

As per the researchers, terror birds, or ‘phorusrhacids’, were the top predators on the South American land mass in the period following the dinosaurs' disappearance about 65 million years ago. According to an earlier study, the birds might have killed their prey with a single blow before setting to work on its flesh.

"They evolved very unique forms, with huge skulls, huge beaks with hooks, and long hindlimbs. They lost their ability to fly and they developed very unusual predatory capabilities that were not present in any comparable animals”, said Dr Degrange, a terror bird specialist who works at the National University of Cordoba.

After the study's senior author Fernando Scaglia, the recently found species is named as Llallawavis scagliali. According to the researchers, it stood about 1.2m tall and maybe weighed 18kg. There is a possibility that it might consume mammals or other birds.

As per the researchers, may be most interesting among the well-preserved details of the fossil is its skull and this enabled the researchers to make some good assumptions about the animal's sensory abilities. So, terror birds had low frequency sensitivity and it has been suggested that they also produced low-frequency sounds.