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Paleontologist Unearths Australia's Earliest Known Bird Tracks

Oct 28, 2013 03:52 PM EDT

Paleontologists have determined that a pair of fossilized footprints found in Dinosaur Cove in Victoria, Australia, were likely made by birds during the Early Cretaceous period, making them the oldest known bird tracks found on the continent.

The find, which is documented in the journal Palaeontology by Anthony Martin, a paleontologist at Emory University in Atlanta, gives a clearer picture of the fauna that existed in the regions eons ago.

"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.

Dinosaur Cove, which represents an ancient river valley that formed during a polar climate as the supercontinent Gondwana broke up and Australia separated from Antarctica, has consistently proven to be a source of important research on the natural history of dinosaurs in Australia and the Southern Hemisphere as a whole. The site has been a wealth of information about dinosaurs, but prior to this fossilized pair of tracks, only one other fossil from a bird had been uncovered at the site.

Martin, who specialized in trace fossils, said the two sets of footprints were likely made by two individual birds about the size of an egret or a small heron.

The footprints were identified as avian from their rear-pointing toes, which distinguished them from other nearby fossilized tracks that were likely made by a non-avian theropod.

Another telltale sign in the fossilized bird prints was a long drag mark on one of them.

"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, adding that a fossilized landing track is a rare find that could add to the current understanding of the evolution of flight.

Martin went on to highlight the connections between dinosaurs and birds, singling out the Tyranosaurus rex, which had a vestigial rear toe, evidence that it shared ancestry 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."

Martin wonders less about the sort of bird that made the track and more about when they were made.

"The biggest question for me," he 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."

He added that these tracks will help paint the picture of early bird evolution in the Southern Hemisphere.

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