June 24, 2008 -- Sometime between 145 and 100 million years ago, a Korean dinosaur ran nearly 11 miles per hour in a straight line next to a lake, according to recent study of footprints left behind by the speedy raptor.
Paleontologists believe the tracks were made by a small dromaeosaurid, which was a carnivorous Velociraptor-like dinosaur. In Greek, the word dromaeosaurid fittingly means "running lizard."
The tracks are quite rare, as they represent the first didactyl, or two-toed, raptor footprints from Korea. Such footprints are only known from two other sites in the world, both in China.
The running dromaeosaurid might have been trying to escape an even larger carnivorous dino, but the researchers can't be certain.
"It was a fast animal, but we do not know if it was influenced by other animals in its behavior," co-author Martin Lockley told Discovery News.
Lockley, a professor of geology and curator of the University of Colorado at Denver Fossil Footprint Collection, and his colleagues found the dinosaur's footprints while working at the Haman Formation on Chu Island in Korea. This is an extremely small island, only about 0.2 miles in length.
The footprints they found consist of two toes per print. Each digit has four attached, concentric pads terminated by a very prominent and sharp raptorial claw.
"This strongly curved and sharp claw was held off the ground surface in normal locomotory situations in order to prevent the ungual from becoming dull with repeated contact against an abrasive substrate, strongly suggesting that it had an offensive function, such as attacking prey," Lockley and his colleagues wrote in a paper summarizing their finds that was recently published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.
Aside from revealing that the dinosaur was in too big of a hurry to kick with its destructive claws, the footprints indicate the animal's hip height, which the researchers calculated as being about 27.5 inches.
Lockley explained that prior research determined "hip height is about five times the footprint length." Speed can then "be calculated from hip height and stride length."
The other two didactyl footprints from China preserved much slower walks. In those cases, the raptor was only moving around 1.1 miles per hour and 3.6 miles per hour, further suggesting that the Korean dinosaur really cranked up its speed for the lakeside run.
Peter Makovicky, assistant curator of Fossil Amphibians and Reptiles at The Field Museum in Chicago, told Discovery News that "a lot of footprints are hard to identify, but I agree with Lockley and his team that these belonged to a clawed raptor."
Makovicky explained that the tracks are "important, because they fill in gaps within the fossil record."
The size, speed and location data will now be added to other didactyl findings, which suggest the meat-eating dinosaurs moved in flocks or herds, although the Korean individual probably ran without a group in that one preserved moment.
He added that this particular dinosaur was about the size of an emu, and might have behaved in a similar manner.
"I once clocked an emu running 55 kilometers per mile (just over 34 mph) while I was in a truck alongside it," Makovicky said. "Like emus, the feathered raptor dinosaur would have been too big to fly, but it certainly could run fast."
Related Links:
How Stuff Works: How Dinosaurs Work
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