The flightless phorusrhacids, which are known as terror birds, were one of the top predators in South America before they went extinct 2.5 million years ago. Scientists have now found one of the most complete fossils of this ancient bird to date.
Scientists have found a nearly complete skeleton of the new species of phorusrhacids known as Llallawavis scagliai and this allowed them to study the creature's anatomy in unprecedented detail, as well as gain more insights about the bird known for its hooked beak and taste for meat.
The discovery, which was reported in the latest issue of the Journal of Vertebrate Paleontology, has more than 90 percent of its skeleton preserved, revealing the hearing capabilities of this predatory bird and marking the first time that structures involving hearing sensitivity were reconstructed for a terror bird. The detailed find may help provide explanation of the behavior, evolution and ecology of this particular group of extinct birds.
Paleontologists said the new species. which lived in Argentina about 3.5 million years ago during the Pliocene Epoch, measured 4 feet tall and had a terrifying appearance. Compared with the birds that currently live today, the fossil bird likely had hearing that was probably below average.
Scientists claim that the flightless bird, whose name means Scaglia's Magnificent Bird after one of the most famous naturalists from Argentina, Galileo Juan Scaglia, had a limited vocal range with low frequency, which raises the idea that the flightless bird may have used low-frequency sounds to detect its prey.
"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 in 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."
Researchers reconstructed the structure of the inner ear of the bird with the aid of 3D computed X-ray tomography and found that the Llallawavis would have a hearing range of about 3,800 Hz and a sensitivity of about 2,300 Hz. The human ear can detect sounds with frequencies that range between 20 Hz and 20,000 Hz, suggesting that the predatory birds were better at detecting lower-frequency sounds compared with humans.
Degrange said that the discovery of this species showed that terror birds were more diverse during the Pliocene period than previously believed. It also allowed scientists to review the hypothesis regarding the decline and extinction of this group of fossil birds.
Photo by: F. Degrange
