Melbourne: Two thin-toed footprints pressed into a sandy riverbank more than 100 million years ago are Australia`s oldest known bird tracks, scientists say.
The fossilised footprints found at Dinosaur Cove in southern Victoria were likely made by birds during the Early Cretaceous period.
Much of the rocky coastal strata of the Dinosaur Cove were formed in river valleys in a polar climate during the Early Cretaceous. A great rift valley formed as the ancient super-continent Gondwana broke up and Australia separated from Antarctica.
Paleontologist Anthony Martin of Emory University said the thin-toed tracks in fluvial sandstone were likely made by two individual birds that were about the size of a great egret or a small heron. Rear-pointing toes helped distinguish the tracks as avian, as opposed to non-avian dinosaurs.
"These tracks are evidence that we had sizable, flying birds living alongside other kinds of dinosaurs on these polar, river floodplains, about 105 million years ago," Martin said.
A long drag mark on one of the two bird tracks particularly interested 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 landing track from Australia 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," said Martin, who carried the analysis along Monash University`s Patricia Vickers-Rich and colleagues.
"Fossils of landing tracks are rare, and could add to our understanding of the evolution of flight," said Martin.
Today`s birds are actually modern-day dinosaurs, and share many characteristics with non-avian dinosaurs that went extinct, such as nesting and burrowing.
The study was published in the journal Palaeontology.