Researchers spotted what may be the oldest-known bird tracks in the world.

The fossilized footprints were found at Dinosaur Cove in Victoria, Australia, and are believed to have been made during the Early Cretaceous an Emory Health Sciences news release reported.

"These tracks are evidence that we had sizeable, flying birds living alongside other kinds of dinosaurs on these polar, river floodplains, about 105 million years ago," Anthony Martin, a paleontologist at Emory University, said.

The tracks were believed to have been made by two birds; both were about the size of small herons. One of the prints had a drag mark on it that excited the researchers.

"I immediately knew what it was -- a flight landing track -- because I've seen many similar tracks made by egrets and herons on the sandy beaches of Georgia," Martin said.

"[The ancient print] has a beautiful skid mark from the back toe dragging in the sand, likely caused as the bird was flapping its wings and coming in for a soft landing," he said.

Martin said it's rare to see these landing tracks in fossil form, and they could help researchers understand the evolution of flight.

Birds are considered to be "modern day dinosaurs," and share some characteristics with extinct non-avian dinosaurs such as nesting and burrowing.

The notorious Tyrannosaurus rex had a vestigial rear toe, which suggests the behemoth had a common ancestor with birds.

"In some dinosaur lineages, that rear toe got longer instead of shorter and made a great adaptation for perching up in trees," Martin said. "Tracks and other trace fossils offer clues to how non-avian dinosaurs and birds evolved and started occupying different ecological niches."

A number of non-avian dinosaur bones have been found in Dinosaur Cove, but only one bird wishbone has turned up.

The tracks are believed to have been made on a wet river bank.

"The biggest question for me," Martin said. "Is whether the birds that made these tracks lived at the site during the polar winter, or migrated there during the spring and summer."

Some of the best records of ancient birds and their connection with dinosaurs have been found in the Liaoning province of Northeastern China. Samples of amber containing preserved feathers and other fossils have been found in the region.  

"In contrast, the picture of early bird evolution in the Southern Hemisphere is mostly incomplete," Martin says, "but with these tracks, it just got a little better."