Ancient bird skull from Antarctica might be from early duck relative

Birds evolved from dinosaurs millions of years ago – but the route from these avian ancestors to now is largely mysterious.

Scientists now have a new waypoint on this journey, thanks to the discovery of a fossil skull from an ancient bird known as Vegavis iaai. While the species itself was named more than 20 years ago, its skull was a mystery until a newly identified fossil was found.

The new skull shares many similarities with living birds, such as a toothless beak and a bird-like braincase. In fact, the study claims that Vegavis might be the oldest known modern bird discovered so far.

“Few birds are as likely to start as many arguments among palaeontologists as Vegavis,” says the study’s lead author, Dr Christopher Torres. “This new fossil is going to help resolve a lot of those arguments. Chief among them: where is Vegavis perched in the bird tree of life?”

Based on similarities in their bones, the researchers believe Vegavis is a relative of living ducks and geese. Its lifestyle, however, seems to have been more like modern diving birds.

Dr Patrick O’Connor, a co-author of the research, says that this “underscores that Antarctica has much to tell us about the earliest stages of modern bird evolution.”

“Those few places with a respectable Late Cretaceous fossil record of birds, like Madagascar, reveal an aviary of bizarre early birds with teeth and long bony tails that are only distantly related to modern birds. Something very different was happening in the far south of Antarctica.”

The findings of the study were published in the journal Nature.

What was Cretaceous Antarctica like?

Antarctica during the Late Cretaceous, around 69 million years ago, was not the frozen continent it is now.

With an average temperature of around 7°C, the southern continent would have been home to heaths, grasslands and lush forests filled with trees and ferns. While these plants wouldn’t have been at risk of freezing temperatures year-round, they would have had to cope with months of darkness during Antarctica’s long polar nights.

These rich ecosystems were roamed by a variety of animals, including dinosaurs such as Imperobator and Morrosaurus. While it would still be millions of years until modern penguins appeared, species like Vegavis show that birds were already living in and around the ocean.

By examining the new skull fossil, the researchers believe that Vegavis would have had powerful jaw muscles. This would have allowed it to close its beak underwater while pursuing prey, a challenge that penguins have also had to overcome.

Unlike penguins, however, Vegavis didn’t swim with its wings. Instead, it seems that the ancient bird took an approach similar to modern grebes and loons and swam using its feet instead.

Together with its other more duck-like features, Vegavis appears to have had a mosaic of different characteristics now found in a range of modern birds.

Living through a mass extinction

The characteristics of the new Vegavis skull also hint at the animal’s closest relatives. Analysis places the bird within the Anseriformes, a group that contains the ducks, geese, swans, screamers and their relatives.

Rather than being a direct ancestor of these birds, Vegavis is believed to belong to an extinct side group known as the presbyornithids. Its own closest relative is a fossil wading bird known as Conflicto, which was also found in Antarctica.

What makes this relationship unusual is that Vegavis and Conflicto lie on either side of the Cretaceous mass extinction. This saw an enormous asteroid strike what’s now Mexico, wiping out the dinosaurs along with three quarters of all species alive at the time.

While birds survived the extinction, it’s actually very rare to have the evidence of two closely related groups – known as sister taxa – on either side of the boundary. In fact, the researchers believe it is currently the only example.

It’s possible that birds had a better chance of surviving in Antarctica because it was relatively far away from the asteroid’s impact, but the scientists don’t yet have enough evidence to prove this.

In the meantime, researchers continue to hunt for fossils in Antarctica, searching for new species buried beneath the icy wilderness.