How the fearsome 'terror bird' dealt with its victims six million years ago

Scientists have worked out how the wonderfully named ‘terror bird’, which died out some two million years ago, caught and chopped up its prey

IT FLOATED like a butterfly and stung like a bee but it was no boxer. Scientists have worked out how the wonderfully named “terror bird” caught and chopped up its prey.

This flightless bird, of the Phorusrachidfamily, ranged across what is now North and South America millions of years ago. And while it might not have had the grace of its flighted raptor cousins, it was a fearsome carnivore, holding a slot as one of the top predators of its day.

It didn’t need to hide up a tree and seemed well able to protect itself against other meat-eaters, given the largest of this family of 18 known species measured 2.1m in height.

It is likely that humans would have been part of its menu plan had we existed at the time. These birds had an unusually large rigid skull that was finished off with a sharp, hatchet-like pointed beak.

While palaeontologists had plenty of fossils of the beast, there are, happily, no modern descendants and for this reason, scientists could only speculate about its habits, how it fed and where it might have fitted in the ecological framework of the time.

Many of these blanks have now been filled in by an international study of one species of terror bird, Andalgalornis, published this morning in the open-access online journal PLoS ONE.

Andalgalornisstalked the pampas of what is now South America six million years ago. It was a mid-range model, standing about 1.4m and weighing in at 40kg. Its skull was huge though, measuring 37cm – more than a quarter of its height.

Straight observation of the fossilised remains revealed little other than the obvious danger of its fearsome beak, so the team used advanced equipment, including CT scanning and engineering methods, in a full biomechanical analysis that helped bring the terror bird to life.

“We need to figure out the ecological role that these amazing birds played if we really want to understand how the unusual ecosystems of South America evolved over the past 60 million years,” says lead author Dr Federico Degrange, of the Museo de La Plata/Conicet, in Argentina.

The scanner gave the team a look at the inner architecture of the skull. "Birds generally have skulls with lots of mobility between the bones, which allows them to have light, but strong, skulls. But we found that Andalgalornishad turned these mobile joints into rigid beams," says co-author Dr Lawrence Witner, of the Ohio University College of Osteopathic Medicine, a professor of palaeontology and anatomy.

The evolution of this large, dangerous weapon was linked to the loss of flight in the terror birds, the authors suggest.

The scans allowed an Australian team of engineers to study stresses and strains on the skull using a technique known as finite element analysis. They simulated a range of attacking and feeding behaviours to see which most closely matched the physiology of the bird based on its fossil remains.

They found that it didn’t have a particularly strong bite, and could not readily shake its head from side to side to slice into prey. Instead, it used its powerful neck muscles to lash out with its sharply pointed beak like a hatchet and then rake backwards to rend open prey.

The authors argue their results suggest Andalgalorniswhen attacking performed something like Muhammad Ali, planting devastating jabs in a repeated attack-and-retreat technique until the prey had been killed. Then the hooked beak would have come into its own, ripping the prey's flesh apart before gulping it down.

The birds would have had to survive against tough competitors, as seen in the fossil record of the time, including a saber-tooth marsupial.

The birds persisted for millions of years, eventually spreading out into North America over the Panamanian land bridge, which formed some 2.5 million years ago.

By this time some of the biggest of the birds appeared, with the most recent fossil of a terror bird, called Titanis, recovered in North America.

Then, abruptly, the birds dropped out of the fossil record, perhaps a suggestion that the creature had finally met its match.

Twitter: @dickahlstrom