August 30, 2013
Terror Bird Not So Terrifying After All
Brett Smith for redOrbit.com - Your Universe Online
In an extreme case of mistaken identity, paleontologists have announced that the 6-foot tall ‘terror bird,' which inhabited Europe between 55 to 40 million years ago, may have been herbivorous and not a meat eater as previously thought.
"The terror bird was thought to have used its huge beak to grab and break the neck of its prey, which is supported by biomechanical modelling of its bite force," said Thomas Tütken, from the University of Bonn. "It lived after the dinosaurs became extinct and at a time when mammals were at an early stage of evolution and relatively small; thus, the terror bird was thought to have been a top predator at that time on land."
In a new report presented at European Association of Geochemistry’s Goldschmidt conference in Florence, Italy on Thursday, Tütken and his colleagues revealed findings about the ancient bird’s fossilized remains indicate that it was probably not a meat eater at all.
American researchers recently found footprints thought to belong to a relative of Gastornis. The prints did not show evidence of sharp claws that would be expected of a carnivorous raptor – casting further doubt on Gastornis’ meat-eating diet ahead of the latest study.
To reach their conclusion, Tütken and his fellow researchers used a calcium isotope analysis to determine the composition of the bird’s fossilized bones. Because the calcium isotope signal gets weaker as it passes down the food chain, the team said they were able to determine much of the creature's diet and their position in the local food chain. Their method was first tested on the remains of herbivorous and carnivorous dinosaurs, including the infamous Tyrannosaurus Rex.
If Gastornis was an apex predator as previously believed, it's fossils should contain a strong calcium isotope signal. However, the team found weak isotope levels in the terror bird remains, unlike the strong levels found in T. Rex and other predators. The paleontologists say the calcium isotope compositions of terror birds are comparable to those of herbivorous mammals and dinosaurs.
"Tooth enamel preserves original geochemical signatures much better than bone, but since Gastornis didn't have any teeth, we've had to work with their bones to do our calcium isotope assay," Tütken said. "Because calcium is a major proportion of bone – around 40 percent by weight – its composition is unlikely to have been affected much by fossilization.”
The team says it plans to verify its initial findings using other fossilized remains.
“We want to be absolutely confident in our findings by analyzing known herbivores and carnivores using fossilized bone from the same site and the same time period,” Tütken added. “This will give us an appropriate reference frame for the terror bird values."
Remains of similar birds have been found in South America and Australia that are believed to be carnivorous. In contrast, all of the large flightless birds today are plant eaters.