Field Notes: The Polar Field Services Newsletter

Journey Through A Deep Time Laboratory


Jaelyn Eberle (far right in blue) and her colleagues take a break from hunting fossils on Ellesmere Island in the Canadian Arctic to enjoy lunch. Photo: Sabine Mehay, MIT

Picture a densely forested, swamp-like terrain with primates swinging in the forest canopy, alligators smoothly gliding through the water, turtles and land tortoises munching on lush vegetation and large hippo-like creatures calling to one another. Now try to place this scene. A wildlife reserve maybe? Africa? No. This was what the High Arctic likely looked like some 52-53 million years ago during the early Eocene Epoch.

Climate and paleontology records tell us the Arctic was home to a drastically different ecosystem supported by much warmer temperatures. With funding from the National Science Foundation, Jaelyn Eberle, curator of fossil vertebrates at the University of Colorado Museum of Natural History and associate professor of geological sciences at the University of Colorado Boulder, has put the spotlight back on some of the long-forgotten fauna that inhabited the Arctic during a very wet and warm phase in the region’s history.

The view from atop a hill on Ellesmere Island. Fifty million years ago, Ellesmere Island looked very different than it does today. It was once warm, wet, densely forested and teeming with ancient animals. Photo: Jaelyn Eberle

Ellesmere Island’s Buried Past

Located in the far northern reaches of the Canadian Arctic just west of Greenland, Ellesmere Island is a dream location to study the Arctic’s faunal changes over the last 50 million years. Today it is one of the coldest, driest places on earth.

The frozen ground holds a rich fossil history from which Eberle and her team were able to glean information about the lifestyles, eating habits and migratory patterns of ancient Arctic fauna, as well as what their surrounding environment was like. In addition to providing a snapshot of the Arctic’s past, the fossils also hold clues to the Arctic’s future as global temperatures rise.

Today, all that’s left of Ellesmere Island’s vast swamp forests are fossilized tree stumps like those pictured here. Scientists are concerned that some of the best areas for studying fossils on Ellesmere Island face potential destruction by coal mining companies. Photo: Jaelyn Eberle

“We’re very interested in looking at fauna from that time interval [the Eocene Epoch] particularly in the Arctic region because what climatologists are finding today is that the Arctic region may be the canary in the coal mine for global warming. By looking at past intervals of global warming—what I call a ‘deep time laboratory’—we can get an idea of the biotic impacts of that particular global warming event,” Eberle explained.

Over the past several years Eberle and a team of researchers from the U.S. and Canada   have spent part of the summer sifting through sediments and delicately extracting the fossil remains of animals and plants. Of all the paleontological findings, the teeth hold many important clues.

You Are What You Eat

You can tell a lot about an animal from its fossil remains, even down to what the creature ate. One animal that fascinated Eberle was Coryphodon, a large, hippo-like herbivore that not only lived in the Arctic, but was also present in mid-latitude locations like Wyoming and Colorado during the Eocene. Curious about Coryphodon’s migratory patterns and how it survived and thrived in the Arctic during the 24 hours of darkness in the winter months, Eberle and colleagues Henry Fricke (Colorado College) and John Humphrey (Colorado School of Mines) analyzed the carbon isotopes left behind in the fossil teeth.

Fossilized teeth of the hippo-like mammal Coryphodon. Eberle and her colleagues conducted carbon and oxygen isotope analyses of the teeth to determine what the animal ate at various times of the year. Photo: Jaelyn Eberle

“Although carbon isotopes can’t tell you an animal’s absolute diet, they can narrow the playing field of which plants (or plant parts) an animal ate. Eberle explained. “Plants each have a distinctive carbon isotope signature that is incorporated into the teeth of herbivorous mammals.”

By comparing the carbon isotope value ranges of the Arctic Coryphodon with that of the mid-latitude population, the team concluded that the Arctic population did not migrate during the winter dark period, but stayed in the Arctic year-round. That result sparked several questions about what Coryphodon ate during the dark winters when most vegetation disappeared.

“In the summer, Arctic Coryphodon had a diet similar to that of the mid-latitude Coryphodon—flowering plants and leaves of some sort. But in the winter, its carbon isotope signature was quite different and suggested the animal was probably incorporating evergreen conifers and leaf litter. We also posed the idea that perhaps they were eating fungi, algae and other aquatic plants,” Eberle said.

Animal Migratory Patterns

A reconstruction of the Eocene High Arctic. A hungry Coryphodon munches on vegetation in a dense forest. Illustration courtesy of the American Museum of Natural History

Arctic Coryphodon data sets do more than tell researchers about the diets of large mammals living in the Arctic 50 million years ago; they also add another piece to the puzzle about how groups of mammals migrated from Asia to North America.

“During the early Eocene we have several groups of mammals that appear in North America. The leading hypothesis is that these animals migrated from Asia across a northern high latitude land bridge. The ‘smoking gun’ is the ability for the animals to stay in the Arctic all year. If they are trudging great distances across an Arctic land bridge from Asia to North America, we would not expect them to do this in one season,” Eberle explained.

Although Coryphodon was among the most abundant animals in the Eocene Arctic, it certainly wasn’t the only creature in the swamp forests.

The Arctic was home to a variety of rodents, the ancestors of tapirs and brontotheres, which are ancient cousins of rhinos. There would have been lots of aquatic turtles, alligators, giant land tortoises and bowfin fishes. “There was a pretty diverse fauna living in (or near) a dense swamp forest,” Eberle said. “We can tell it was pretty swampy based on the thick coal deposits and the plant fossils that we’re finding.”

Ancient Mammals Brought Back to Life (Sort of)

Fortunately for those outside the paleontological sphere, the fossils that Eberle and her colleagues unearth don’t sit untouched in an Indiana Jones-style warehouse. Many of the fossils are exhibited in museums in the United States and Canada.

 

A reconstruction of an ancient Arctic tapir. Today, tapirs are found in South and Central America and Southeast Asia. Illustration courtesy of the American Museum of Natural History

“All of the material that we collect in Canada belongs to Canada. Once we are finished studying the material, we send it all back to Canada to the Canadian Museum of Nature in Ottawa, which is the equivalent of the Smithsonian. And some of it is on exhibit already,” she said. Her research has also been incorporated in to the “Extreme Mammals” travelling exhibit at the American Museum of Natural History in New York.

“I described a tapir from the High Arctic a few years ago and scientists at the American Museum of Natural History were able to reconstruct him. It was so cool! I can’t think of anything much cooler for a paleontologist to see their animal on exhibit.”

To learn more about Jaelyn Eberle’s work on Eocene mammal fossils in the High Arctic, visit: http://www.colorado.edu/GeolSci/faculty/eberle.html. To read the peer-reviewed paper on this work published in GEOLOGY (June 2009) download the PDF.  —Alicia Clarke

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