Today's birds are actually modern-day dinosaurs, and share many characteristics with non-avian dinosaurs that went extinct, such as nesting and burrowing. (Martin previously discovered the trace fossils of non-avian dinosaur burrows, including at a site along the coast of Victoria.)
The theropod carnivore Tyrannosaurus rex had a vestigial rear toe, evidence that T. rex shared 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 says. "Tracks and other trace fossils offer clues to how non-avian dinosaurs and birds evolved and started occupying different ecological niches."
Dinosaur Cove has yielded a rich trove of non-avian dinosaur bones from dozens of species, but only one skeletal piece of a bird a fossilized wishbone has been found in the Cretaceous rocks of Victoria.
Martin spotted the first known dinosaur trackway of Victoria in 2010 and a few other tracks have been discovered since then. Volunteers working in Dinosaur Cove found these latest tracks on a slab of rock, and Martin later analyzed them.
The tracks were made on the moist sand of a river bank, perhaps following a polar winter, after spring and summer flood waters had subsided, Martin says. "The biggest question for me," he adds, "is whether the birds that made these tracks lived at the site during the polar winter, or migrated there during the spring and summer."
One of the best records of the dinosaur-bird connection has come from discoveries in Liaoning province of Northeastern China, including fossils of non-avian dinosaurs with feathers. Samples of amber have also been found in Liaoning, containing preserved feathers from both birds and non-avian dinosaurs going back t
|Contact: Beverly Clark|
Emory Health Sciences