Friday, July 29, 2016

Dinosaur tracks lead paleontologist through museum to mentor's discovery

One of the ornithopod tracks from Skenes Creek (left), placed next to the Knowledge Creek one, showing how closely they match. Photo by Anthony Martin.

By Carol Clark

Paleontologists don’t always have to go into the field in search of fossils to identify. Sometimes they dig through the collections of museums.

That was the case for the latest paper by Emory paleontologist Anthony Martin, published in the journal Memoirs of Museum Victoria. Martin describes the first dinosaur tracks found in Victoria, Australia – way back in the 1980s – and explains their paleontological importance.

The three footprints, made by small ornithopods, were recovered in Lower Cretaceous strata of the Eumeralla Formation of Victoria, dating to about 105 million years ago. One of the tracks was found at Knowledge Creek in 1980 by paleontologists Thomas Rich and Patricia Vickers-Rich, a husband and wife team. The other two prints were spotted in 1989 at Skenes Creek by geologist Helmut Tracksdorf.

Martin’s study appears in a special volume honoring the career of Thomas Rich, a long-term mentor of Martin.

“The article documents a presence of small ornithopod dinosaurs in Victoria, matching a skeletal record,” Martin says. “It’s scientifically significant because these were polar dinosaur tracks and, unlike bones, they show exactly where those animals were living. Small dinosaurs were much less likely to migrate far, and these tracks suggest that they had adapted to year-round living in a polar environment.”

Victoria is famous for its polar dinosaur bones, which washed downstream during torrential spring flooding and were deposited on the banks of rivers, far from the sites where the animals actually lived and died, Martin explains.

Tracks, however, pinpoint where the dinosaurs actually set foot.

Martin is an expert in trace fossils, which include tracks, trails, burrows, cocoons and nests. In 2006, while looking for dinosaur tracks, he discovered the first trace fossil of a dinosaur burrow in Australia, at Knowledge Creek on the Victoria coast. In 2011, Martin, Rich and Vickers-Rich published their find of more than 20 polar dinosaur tracks at Victoria’s Milanesia Beach, the largest and best collection of polar dinosaur tracks ever found in the Southern Hemisphere.

The Victoria coast marks the seam where Australia was once joined to Antarctica. During that era, about 115 to 105 million years ago, the dinosaurs roamed in prolonged polar darkness. The Earth’s average air temperature was 68 degrees Fahrenheit – 10 degrees warmer than today – and the spring thaws would have caused torrential flooding in the river valleys.

The ornithopods (Greek for “bird feet”) had three toes. The ones that made the three tracks in Martin’s current study were bipedal grazers that stood about three feet tall.

While most dinosaur tracks are depressions, these three tracks are all raised. “Somehow, the tracks changed the character of the sediment, compacting the sand underneath them in a way that led to differential weathering,” Martin says.

The specimens are part of the collection of the Museum Victoria in Melbourne. “Museum collections serve an extremely important role by keeping specimens safe and giving scientists over generations a chance to study, and to re-study them,” Martin says. “As technology changes, who knows what new information we can get by re-examining old specimens?”

Polar dinosaur tracks open new trail to past
Dinosaur burrows yield clues to climate change 

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