November 26, 2007
Emory paleontologist tracks clues to ancient life
By Carol Clark
Anthony Martin, a paleontologist and senior lecturer in environmental studies, recently made international science news for detecting the first carnivorous dinosaur tracks at a site in Victoria, Australia. He attributes the discovery to his passion for tracking modern-day animals.
"I look for all kinds of animal tracks, across all kinds of substrates — beach sand, gravel, mud, pine needles and leaves," Martin says. "I track our cat across the carpet at home. It drives him nuts. I'll follow his little, round prints into the closet and he'll look up at me like, 'Wait a minute! You're not supposed to know I'm here!'"
While many paleontologists are looking for fossilized bones, Martin is fixated on indirect evidence of plants and animals that inhabited the earth millions of years ago. Known as trace fossils, such evidence of ancient life includes tracks, trails, burrows, nests — even feces.
On his desk in the Math and Science Building are dinosaur bones recently uncovered by researchers in Alaska. "I personally don't work with fossilized bones, these are just on loan, for educational purposes," Martin says, picking up a 70-million-year-old hadrosaur tibia.
He exchanges the tibia for a finger-sized, globular clump of what looks like hardened mud. It's actually a fossilized insect burrow, most likely made by halictid bees that were buzzing about 75 million years ago. "This to me is much more exciting than bones because it gives me direct evidence about behavior," Martin says. "Why were the insects burrowing into the soil and why did they pick that particular soil to burrow in? What's cool is that you can use trace fossils to get into the ecology of millions of years ago."
Martin was also part of a team that discovered the first trace and body fossil evidence of a burrowing dinosaur, at a site in Montana.
Can students become as intrigued by ancient burrows and animal tracks as they can by actual dinosaur bones?
"They can if I get a hold of them," Martin says. He teaches a freshman seminar called "How to Interpret Behavior You Did Not See" which takes students on tracking expeditions to Lullwater preserve.
"Tracking expands your world," he says.
For instance, not many people realize that deer roam the Emory campus. Martin and his students have identified deer tracks, along with those of beaver, gray foxes and river otters in Lullwater
One of Martin's favorite Lullwater finds was the track of a red fox, along the south fork of Peachtree Creek. "I saw this beautiful, perfect print and I thought, ‘Wow! There are red foxes in Lullwater,’" he recalls. A small bar on the heel and furry pads are two ways to distinguish fox prints from those of domestic dogs.
"Wild canines behave very differently from domestic dogs, and that also shows up in their tracks," Martin says. He lets his tongue loll out, pants, and punches the air with his hands in all directions, mimicking a frisky pet out for a walk. "Wild canines are much more purposeful, their tracks are all business," he says. He whips his right arm out in front of him, precisely followed by his left, to show how a fox trots.
In the spring of 2006, Martin used a Winship Award from Emory College to spend time at Monash University in Melbourne, Australia, home to the School of Geosciences and the Monash Science Centre. The center is directed by Patricia Vickers-Rich, a paleontologist whose public outreach and research Martin had long admired.
One of the Winship projects Martin proposed was to research animal tracking in indigenous Australian cultures. "I'm constantly moving between examples of modern tracks and ancient ones," Martin says. "I think it makes me a better paleontologist."
Martin accompanied Murrindindi, a tribal elder of the Wurrundjeri aboriginal clan, on a tracking expedition. "He'd say, 'Here's where a platypus came up on shore.' He'd notice a part of the riverbank that was a little more damp and say, 'That's where the platypus was lying.' And sure enough, if you looked closely you'd see the tracks," Martin says, admiringly.
One day, on a lark, Martin accompanied Thomas Rich, a paleontologist from the Museum of Victoria and the husband of Vickers-Rich, to the Dinosaur Dreaming dig site near the coastal town of Inverloch. The Victoria coast marks the seam where Australia was once joined to Antarctica. Lower Cretaceous strata of Victoria have yielded a sizeable amount of dinosaur bones since the late 1970s, resulting in the best-documented polar dinosaur assemblage in the world. However, only one dinosaur track, from a small herbivorous dinosaur, had ever been found.
Making his mark
Martin immediately began walking along the shore, looking closely at the rocks. "You won't find anything," Rich warned him, letting him know that many other paleontologists had tried and failed to find tracks.
But within hours of his arrival, Martin detected what seemed to be the fossilized trace of a dinosaur toe print. That same day, he found a second track that was equally subtle. "I have so much experience with dinosaur tracks, as well as tracking modern animals, that I can spot incomplete tracks," Martin says. "I see toe prints. I see claw impressions. I just see all these things."
Encouraged by Martin's find, workers at the site kept an eye out for more tracks. A year later, in February 2007, Monash undergraduate student Tyler Lamb discovered a third track — a complete one showing all three toes.
Martin (who is now an honorary research associate at Monash), Rich, Vickers-Rich and Lesley Kool, another paleontologist from Monash, published a paper on the tracks, after determining that they were made by large carnivorous dinosaurs (theropods) during the Cretaceous Period. Based on the 14-inch length of the tracks, the scientists estimate that the theropods measured 4.6 to 4.9 feet at hip height.
Martin explains how a dinosaur stepped into the wet sand of a river floodplain, creating a depression. Water ran over the depression and filled it with coarser-grained sand that had just the right mineral mix to harden like concrete. Floating plant debris was deposited around the edges, leaving black traces that help define its outline. Modern tides and waves are wearing away the softer material surrounding the track.
"One hundred and fifteen million years later, it's just now revealing itself to us," Martin says.