The investigations that have done previous suggested that the giant bird was a carnivorous predator or scavenger. But due to absence of raptor like claws in the footprints supports the theory that Diatryma was not a meat eater.
A team of researchers from Washington, US, examined tracks uncovered in a landslide in 2009.
The giant flightless bird Diatryma is commonly illustrated as a fierce predator in both scientific works and popular media. It was 7 ft (2.13m) tall with a huge head and beak. According to geologist and team member George Mustoe, Western Washington University in Bellingham, US, “it is thought as the bird that replaced dinosaurs as the top predator”.
The study, published in the journal Paleontology, analysed a set of footprints made 55.8 to 48.6 million years ago in the Lower Eocene. Preserved in sandstone, the prints formed part of the Chuckanut Formation in northwest Washington, US.
The team concluded that the multiple, well-preserved tracks were most likely to have been made by Diatryma.
That would make them the only known footprints left behind by this giant bird, and they provide new evidence about what it ate.
“This argues against an animal that catches prey and uses claws to hold it down. Carnivorous birds all have sharp, long talons.”
Early palaeontologists studying Diatryma fossils concluded that the giant bird was a predator because of its size, huge head and large beak.
The first Diatryma skeleton found in the US was preserved alongside bones of tiny horses and other small mammals. Some scientists posited that these must have been the bird’s prey, explained Mr Mustoe.
However, Diatryma also had relatively short legs, leading others to suggest it could not have run fast enough to capture prey, and was therefore a herbivore.
The research team’s conclusion that the animal did not have talons “[adds] ammunition to the herbivory diet hypothesis”, Mr Tucker told BBC Nature.
“A more likely scenario [than being a carnivore] would be a gentle Diatryma that used its beak to harvest foliage, fruits, and seeds from the subtropical forests that it inhabited,” Mr Mustoe added.
The team believe that the similarities of Diatryma to those of the carnivorous South American Phorusracids or “terror birds” led early palaeontologists to assume that the two were ecologically similar.
According to the study: “The common belief that Diatryma… was likewise a carnivore is more a result of guilt by association than actual anatomical evidence”.
– Michelle Warwicker BBC Nature