Researchers Discover Bird Footprints Made 120 Million Years Ago

Researchers have discovered a set of a prehistoric bird footprints that date back to at least 120 million years ago.

The tracks were found on the rocky coast of the state of Victoria in southeastern Australia, according to a study published in the journal PLOS ONE on Wednesday that describes the fossilized footprints.

The tracks represent the oldest known evidence of birds living in Australia, or indeed anywhere in the southern hemisphere.

Evidence suggests that birds began to evolve from dinosaurs around 160-150 million years ago in the Northern Hemisphere near the end of the Jurassic period (around 201 million to 145 million years ago). (Birds are considered to be the only living dinosaurs.)

Early birds then diversified throughout the remainder of the Jurassic and into the Cretaceous period (around 145-66 million years ago), becoming capable flyers in the process.

But while bird fossils from the Cretaceous period are abundant and diverse in the Northern Hemisphere, they are extremely rare in the Southern. This lack of fossils present a challenge for paleontologists trying to understand the distribution of early birds.

Most of the landmasses in today's Southern Hemisphere—including Antarctica, South America, Africa, Australia and New Zealand—once formed part of an ancient supercontinent known as Gondwana. As such, the latest findings also represent the oldest known evidence of birds living in ancient Gondwana.

"Our study shows that a variety of birds were living in Australia much earlier than we expected from their fossil record there and other parts of the southern hemisphere," Anthony Martin, an author of the latest study at Emory University in Atlanta, told Newsweek.

"Because Australia was connected to Antarctica then, and this part of Australia was near the south pole, these are also the oldest bird tracks from a formerly polar environment," Martin said.

Nearly all of the ancient footprints documented in the study were discovered by one of the co-authors Melissa Lowery—a researcher at Monash University in Australia—between 2020 and 2022 near the town of Inverloch. The remainder were noticed by Martin during a subsequent visit in May 2022.

"During the COVID-19 pandemic, [Lowery] and her husband Adrian regularly walked along the coast to look for fossils, including fossil footprints. So I'm pleased to say that she not only found fossil tracks, she found a lot of them!" Martin said.

In total, the authors of the latest study documented 27 tracks, 26 of which were identified at a site dubbed the "Footprint Flats." The researchers documented another track at a separate location nicknamed "Honey Bay" that lies just under a mile to the southwest of Footprint Flats.

When Martin first saw pictures of the ancient footprints sent to him by Lowery, he thought they might have been made by dinosaurs. But investigations revealed that birds were the likely culprits.

"The bird footprints range from small to large, from about 2.75 to 5.5 inches wide," Martin said. "Most tracks have three thin toe imprints that end with sharp claws, and with wide angles between those toes, which is typical for modern birds. But a few tracks also have a short rear toe, which is exactly the type of foot we see in modern birds that perch on tree branches."

The footprints are attributable to several different types of birds, including some of the largest known from the Cretaceous period.

"The larger tracks resemble those made by modern wading birds, such as herons or egrets, and the smaller tracks are like those made by modern shorebirds, like oystercatchers," Martin said. "Because these bird tracks are more than 120 million years old, all of their species are extinct, but some of their distantly evolved descendants might be still with us today."

The footprints were found in rocks that form part of the coastal Wonthaggi geological formation, which marks the site where Australia separated from Gondwana millions of years ago as the ancient supercontinent broke up.

"The footprints are in rocks dated to the Early Cretaceous Period, from at least 120 million years ago, but they might be as old as 128 million years," Martin said. "These ages are based mostly on fossil pollen in the rocks, which is directly linked to trees living then. Australian paleontologists have also found dinosaur bones and other fossils nearby that help confirm ages of the rocks there."

The latest findings indicate that by around 120 million years ago, not long after their origin, birds had diversified and spread throughout much of the world, including into polar regions, according to Martin.

"This diversity and spread also implies that birds may have been migrating seasonally then, flying long distances between one home and another each year," Martin said. "So we hope our results help paleontologists to find more Early Cretaceous bird tracks in other parts of the world, giving us a more complete picture of birds' early evolutionary history."

Silvina de Valais, a researcher with the Research Institute of Paleobiology and Geology in General Roca, Argentina, who was not involved in the latest study, told Newsweek the findings are significant, in part, because ancient bird footprints are not as abundant as experts would like, even though they are found in many parts of the world.

"Any discovery of this type is always important because it contributes in a precise way to reconstructing the ecosystems of the past, considering both the organisms and the environment that made them up," de Valais said.