Winter 2008: Of Note
Tracking Ancient Life
Paleontologist Anthony Martin uses old skills to make new discoveries
By Carol Clark
You’ve seen it in old movies: a Native American or a rugged frontiersman kneels to examine tracks on the ground, following the trail of a bear, deer, or two-legged enemy. Nowadays, hunting is a pastime, not a necessity, and tracking skills are hardly required for modern existence. But Anthony Martin, a paleontologist and senior lecturer in environmental studies, has a keen eye and an abiding appreciation for tracking animals. Martin recently made international science news for detecting the first carnivorous dinosaur tracks in Victoria, Australia.
“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.”
While many paleontologists are looking for fossilized bones, Martin is more interested in 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 Center are dinosaur bones recently uncovered by researchers in Alaska. “I personally don’t work with fossilized bones. These are just on loan,” Martin says, picking up a seventy-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 seventy-five 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 part of a team that discovered the first trace- and body-fossil evidence of a burrowing dinosaur at a site in Montana.
In spring 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 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.
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 fourteen-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.
Can students become as intrigued by ancient burrows and animal tracks as they can by actual dinosaur bones?
“They can if I get hold of them,” Martin says. He teaches a first-year 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. A small bar on the heel and furry pads distinguish fox prints from those of domestic dogs.
“I saw this beautiful, perfect print, and I thought, ‘Wow! There are red foxes in Lullwater,’ ” Martin recalls.
Martin encourages his students to follow such tracks. You never know when they might lead to a new discovery.