Terror Birds' Fossil Show They Stalked Preys By Listening To Footsteps, Had Low Frequency Voice

Scientists, who found a nearly complete skeleton of a new species of the “terror bird,” or "phorusrhacids," in 2010, have learnt further details about the species’ hearing and anatomy.

Federico Degrange, an assistant researcher of vertebrate paleontology at the Centro de Investigaciones en Ciencias de la Tierra and the Universidad Nacional de Córdoba in Argentina, is leading the study into the nearly complete fossil, which was found on a beach in Mar del Plata, a city on the eastern coast of Argentina. The findings from the study were reported Thursday in the Journal of Vertebrate Paleontology.

The scientists reconstructed the inner ear of the terror bird. The analysis of the fossilized flightless bird showed that it could hear low-frequency sounds, which it used for hunting by listening to the prey’s footsteps. New findings also reportedly indicated that the species communicated using these low frequency sounds, researchers said, according to Live Science.

"They evolved very unique forms, with huge skulls, huge beaks with hooks, and long hindlimbs," Degrange said, according to the BBC, adding: "They lost their ability to fly and they developed very unusual predatory capabilities that were not present in any comparable animals."

"We are able to say that terror birds had low frequency sensitivity - so it seems reasonable to suggest that they also produced low-frequency sounds."

The carnivorous species is expected to have been 10-foot-tall, and used to roam in the regions of South America nearly 3.5 million years ago.

The scientists named the newly found species with hooked beaks, "Llallawavis scagliai," because the word "Llallawa" means "magnificent" in Quechua, the native language of the people in central Andes. "Avis" means "bird" in Latin, Live Science reported. The researchers also plan to study the bird’s eye bones, brain case and skull in the following years.

"Terror birds didn't have a strong bite force, but they were capable of killing prey just by striking up and down with the beak," Degrange said, according to Live Science.

The researchers said that one of the main challenges was dealing with the tides near the finding site. "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," Degrange said, according to the BBC News.

The specimen is the first known fossilized terror bird, which has reportedly been found with a complete trachea and complete roof of the mouth. The species’ ears, eye sockets, brain box and skull were also found, providing scientists a clearer picture about the bird’s sensory capabilities.