Two thin-toed footprints pressed into a sandy riverbank more than 100 million years ago are Australia's oldest known bird tracks, researchers say.
The prints were found among the fossil-rich cliffs of Dinosaur Cove on the coast of southern Victoria. Researchers think the tracks were left by a prehistoric bird species likely the size of a great egret or a small heron during the Early Cretaceous Period.
At that time, the world was warmer and the continents were arranged in different positions than they are today. The site of Dinosaur Cove was located in a floodplain in a great rift valley that formed as the supercontinent Gondwana started breaking apart, tearing Australia away from Antarctica. [Avian Ancestors: Dinosaurs That Learned to Fly]
A long drag mark leading up to one of the fossilized footprints was a telltale sign that these tracks were left by flying creatures, explained study researcher Anthony Martin, a paleontologist at Emory University in Atlanta.
The bird tracks were found very close to another footprint that looks like it was left by a non-avian theropod, possibly one of the coelurosaurs, the group of dinosaurs most closely related to birds that includes beasts like the Tyrannosaurus rex.