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Dinosaur expert's 2-track mind

The footprints and behavior of captive emus give a U.S. paleontologist ideas on traces set in stone.

March 04, 2007|Mead Gruver | Associated Press Writer

LIVERMORE, COLO. — Squatting in a small corral in a picturesque Rocky Mountain valley, paleontologist Brent Breithaupt points excitedly at a patch of mud containing a large, fresh, three-toed footprint.

"Everything that we see in this track here can be found in the fossil record," he says.

Nearby, a sound like bongo drumming comes from the throat of a 5-foot, flightless bird with coarse brown feathers. It's an emu, one of about a dozen loping around the corral.

Breithaupt, who is curator of the University of Wyoming Geological Museum, says watching emus and studying their tracks have given him clues about a mysterious dinosaur species from the middle Jurassic period, 165 million years ago.

The similarities between emu tracks and fossilized dinosaur tracks at a site in Wyoming are remarkable:

* Both are two-legged;

* Both have three long, narrow toes;

* Both have indentations from claws at the tips of those toes;

* The tracks have similar padding;

* The tracks are roughly the same size -- 4 to 5 inches, although some of the dinosaur tracks are as large as 8 inches.

Plenty is known about emus, natives of Australia that are raised for their oil, feathers, meat and extra-jumbo green eggs. But precious little is known about whatever dinosaur species made thousands of tracks at Red Gulch in northern Wyoming. In fact, few mid-Jurassic dinosaur fossils have ever been found in North America.

"We don't find the dinosaur dead in its tracks, and so we don't really know," Breithaupt said. "If we ever do find the bones, it will be new to science."

Breithaupt is pretty sure the Red Gulch dinosaurs were a type of theropod, a wide-ranging group of two-legged, short-armed meat-eaters that included the mighty Tyrannosaurus rex. He uses a formula that applies to all sorts of bipeds to estimate the dinosaurs' size: Foot length times four roughly equals hip height.

"Take your basic emu there, put a long dinosaur tail on it, put a slightly different neck and head on it, that's about the size we have," he said.

By observing emus and studying their tracks at Rabbit Creek Enterprises, an emu farm in northern Colorado, he's gone a step further. He has a few ideas about the dinosaurs' behavior.

Breithaupt may have put a riddle about the dinosaur tracks to rest: Why did their feet sometimes cross in front of each other when they walked?

Emus, Breithaupt has noticed, often look around as they walk.

If they see something to their left, they'll cross their right foot over to the left side, stop, and look in that direction. They might then see something to their right. Same thing: They cross their left foot over to the right, stop, and look right.

Also, the dinosaur tracks occur in sync with one another, suggesting they walked in groups and were gregarious. Emus, it turns out, are gregarious as well. At Rabbit Creek, they pace around the edges of their corral in threes and fours.

Breithaupt is interested as well in watching how tracks are made. By observing how emu tracks vary in depth and shape in different types of soil, he can draw conclusions about the ground consistency where the dinosaurs were stepping.

"This is all the kinds of information that we need for figuring out what was going on with the dinosaurs," he said.

Those acquainted with Breithaupt's work say he's on the right track.

"It's a good line of research," said Martin Lockley, a University of Colorado geology professor. "Because with dinosaurs, you can't watch them and know the conditions they're making tracks in."

Matt Carrano, curator of dinosaurs at the Smithsonian Institution, said little is known about how to interpret dinosaur tracks, even though lots of them have been found worldwide.

"There are not a great number of studies to work with, where we've developed a good understanding of how they're made and what sorts of behaviors they reflect," he said.

Breithaupt presented his findings Oct. 25 at the annual meeting of the Geological Society of America in Philadelphia. He hopes to publish a paper on his emu research later this year in Ichnos, a journal covering dinosaur tracks and other types of trace fossils.

Neffra Matthews, a geographer for the U.S. Bureau of Land Management in Denver, has photographed emu and dinosaur tracks for Breithaupt's research. She said emus opened up her own imagination about dinosaurs.

"Working with the emus, they're very inquisitive. And it's very interesting watching them interact with each other, and then watching them interact with me," she said.

She now imagines dinosaurs behaving much like emus.

"I can picture them coming up to each other, like maybe a group of schoolchildren," she said. "And they're poking at each other and they're talking back and forth or they're communicating in some way."

The similarities between emu and dinosaur tracks don't surprise paleontologists, most of whom believe that birds either descended from dinosaurs or are otherwise related.

Not unlike shorebirds, the Red Gulch dinosaurs walked on the shore of the Sundance Sea, a shallow, warm body of water that covered much of Canada and the west-central United States. Breithaupt theorizes that the dinosaurs were feeding on crustaceans or lugworms.

"We can see nice ripples on that surface," he said. "We can see places where the animals burrowed into the ground, those invertebrates burrowed into the ground."

Low tide exposed a tidal flat hundreds of feet wide. Breithaupt believes the dinosaurs' feet sank fairly deep and bottomed out at a firmer layer. It's that layer -- made up of oolites, fine sand grains coated by limestone and cemented together -- that's preserved.

The tracks are similar to others found in Utah, making Breithaupt suspect that the same species lived in both areas.

"It's easy here because we have our usual suspects," Breithaupt said. "... we have to use all of the clues, all of the evidence available to us, to tell us something about ancient Wyoming."

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