Melissa Lowery was out looking for dinosaur fossils at a spot on Australia’s south coast where she’d found scores before, when she looked down at her feet.
“The shadows fell into these gorgeous little shapes, they were so familiar. I stood staring at these shapes for around 10 minutes,” says Lowery, a volunteer fossil hunter.
She reached down and placed her hand into one of the shapes. “It was a moment of pure joy and total wonder as I realised that I had found some footprints.”
What Lowery had found on the rocky flats at low tide was what scientists say is the oldest known evidence for ancient birds in the southern hemisphere – impressions of footprints that have survived for between 120m and 128m years.
The discovery of the 27 bird tracks – initially thought to have been made by dinosaurs – are at a spot that would have been close to the south pole and part of the Gondwana super-continent that included Antarctica when they were made.
Prof Anthony Martin, a palaeontologist at Emory University in Atlanta, was sent pictures of the tracks by Lowery after she found them in the summer of 2000.
Martin, who is a lead author on a scientific paper describing the discovery, says he initially thought they were small dinosaur tracks similar to others found in the same region.
But after a Covid travel ban lifted, he went to the site near the Victorian town of Inverloch, about 150km east of Melbourne. Within a couple of days, he was convinced Lowery’s dinosaur tracks were actually bird footprints.
“As an avid bird watcher for many years, to hear that I had found the footprints of birds was absolutely amazing,” says Lowery, who volunteers for Dinosaur Dreaming, a joint project between Museums Victoria, Monash University and Swinburne University of Technology looking for dinosaur evidence.
Martin used a checklist to distinguish the tracks as birds, including how the prints had three forward-facing widely spread toes at an angle greater than 90 degrees, with sharp claws and some with a distinctive claw for perching.
The birds had possibly migrated there for the spring or summer and were likely about the same size as a modern-day heron or oystercatcher.
“We would have recognised them as birds – a small and feathery animal with a slight build,” Martin tells Guardian Australia. “But as you stared at it, it would look weirder and weirder.
“It would open its mouth and you would see teeth. And it has a tail, with no tail feathers. You would see it’s a transitional animal from its dinosaur ancestors.”
Martin says the tracks are the earliest evidence of birds in Australia, the southern hemisphere and the ancient Gondwana continent.
“This shows us when birds arrived there. We think birds originated about 160 to 150 million years ago in the northern hemisphere,” he says.
The previous earliest known evidence for birds in Australia was from a 105m-year-old fossilised bone also found close to the site of the tracks. The first Australian dinosaur fossil was discovered at the same site in 1903.
The footprints are only visible at low tide but are being eroded by the daily tides. Over the course of 18 months, the study says seven of the tracks had been erased, but not before photographs and casts were made.
Dr Tom Rich, senior curator of vertebrate paleontology at Museum Victoria’s research institute, says: “With a footprint, you know the animal was right there. A bone can move, but a footprint can’t. When you find dinosaurs and bird footprints together, you know they were contemporaneous.”
Rich has been studying the site with his wife, Patricia Vickers-Rich, of Monash University, for about 40 years. Both are co-authors of the study in the journal PLOS One.
“This is one of the few places where you have fossil records of birds and dinosaurs [together] living in a polar region,” Vickers-Rich says.
Rich says once a bird has made its mark on the mud or sand, the impression must have been quickly covered by sediment.
Eventually the mud turned to rock and sank as much as 2km, before being pushed up to the surface as mountains formed, leaving the prints exposed at the current site.
