PARIS – A giant “terror bird” deemed to have been one of Earth’s top predators after the demise of the dinosaurs was in fact probably a plant-loving herbivore, German scientists have reported.
Paleontologists have wrangled for years about Gastornis, a huge flightless bird that lived between 40 million and 55 million years ago.
Up to 2 meters tall, Gastornis had a massive beak with a hooked top — a feature that looks so ferocious that many experts conclude the creature must have been a meat-eater, hence the terror bird moniker.
“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 modeling of its bite force,” said University of Bonn geochemist Thomas Tuetken, who took part in a new assessment.
“It lived after the dinosaurs became extinct and at a time when mammals were at an early stage of evolution and relatively small. “The terror bird was thought to have been a top predator at that time on land.”
Tuetken and his colleagues, though, reassessed the bird’s diet. They began to forge a pro-veggie opinion after they measured calcium isotopes in fossilized Gastornis bones found in a former open-cast brown-coal mine in Saxony-Anhalt, eastern Germany.
The residual signal of these isotopes tells what proportion of the animal’s diet came from meat as opposed to plants. The indicator gets lighter as the isotope passes up the food chain because heavier isotopes are absorbed by the body less readily.
In theory, the bones of a supposed apex predator like Gastornis should have sent a strong signal.
But the team found the isotope levels were weak, similar to those of herbivorous mammals and dinosaurs held in museum collections. Carnivores, including Tyrannosaurus rex, had a far stronger signature.