Big birds serve as stand-ins for dinosaurs

By Mead Gruver

updated 1:59 p.m. ET Jan. 29, 2007

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 (1.5-meter), 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 a few clues about a mysterious dinosaur species from the middle Jurassic, 165 million years ago.

The similarities between emu tracks and fossilized dinosaur tracks at a site in Wyoming are indeed 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 — most 4 to 5 inches (10 to 13 centimeters), although some of the dinosaur tracks are as large as 8 inches (20 centimeters).

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, very 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."

Cousins of T. rex
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.

INTERACTIVE

"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 one another 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.

A gregarious bunch
Also, the dinosaur tracks occur in synch 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.

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