Fossils recovered from Antarctica four decades ago belonged to an ancient, massive toothed bird.

The bird belonged to a now-extinct group of birds called pelagornithids and boasted a wingspan of up to 21 feet. That easily makes it dwarf today’s largest bird, the wandering albatross, which can grow up to a 11½-foot wingspan.

It also kind of had teeth.

Biggest bird

The pelagornithids filled an ecological niche similar to that of albatrosses today — they would soar high above the Earth’s oceans feeding on fish and other marine wildlife. They seem to have been especially well-tailored to the task as the pelagornithids kept doing it for at least 60 million years.

We know of this family of birds from a (much smaller) pelagornithid fossil dating from around 62 million years ago. The new fossil however (a partial fossil of the bird’s food), is some 50 million years old and shows that much larger pelagornithids evolved following the mass extinction 65 million years ago when the dinosaurs went extinct. A second pelagornithid fossil, part of a jaw bone, dates from about 40 million years ago.

“Our fossil discovery, with its estimate of a 5-to-6-meter wingspan — nearly 20 feet — shows that birds evolved to a truly gigantic size relatively quickly after the extinction of the dinosaurs and ruled over the oceans for millions of years,” said first author Peter Kloess, a graduate student at the University of California (UC), Berkeley.

Pelagornithids are known as ‘bony-toothed’ birds. They don’t actually have teeth, but they do have bony protrusions (‘struts’) on their jaws that resemble teeth. They don’t have the internal structures that our teeth do, but they are covered in a layer of keratin (the same material in our fingernails and in animal horns). We call them pseudoteeth (lit. ‘false teeth’), and their purpose is to help the bird catch and hold onto slippery prey such as fish or squid on their week-long flights.

Of course, what was most striking about this extinct bird is its sheer size. Large flying animals have made several appearances in the Earth’s past, with the largest known being the pterosaurs, dinosaurs with wingspans of up to 33 feet.

The newly-discovered pelagornithid grew even larger than teratorns — an extinct family of very large birds of prey native to North and South America, which included some of the largest flying birds ever found.

“[Teratorns] evolved wingspans close to what we see in these bony-toothed birds (pelagornithids),” said Poust. “However, in terms of time, teratorns come in second place with their giant size, having evolved 40 million years after these pelagornithids lived. The extreme, giant size of these extinct birds is unsurpassed in ocean habitats.”

The fossils were first discovered in the mid-1980s on Seymour Island, close to the Antarctic Peninsula by UC Riverside paleontologists. They were transferred to UC Museum of Paleontology, where Kloess stumbled upon them as a graduate student in 2015.

To the best of our knowledge, the last pelagornithid died off around 2.5 million years ago as the last Ice Age began.

The paper “Earliest fossils of giant-sized bony-toothed birds (Aves: Pelagornithidae) from the Eocene of Seymour Island, Antarctica” has been published in the journal Scientific Reports.