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Fossilized footprints show running dinosaur

CAMBRIDGE, England (CNN) -- You can run, but you can't hide, as the saying goes. And a dinosaur that broke into a run 163 million years ago unwittingly left behind a set of footprints that scientists say will help them better understand how dinosaurs known as theropods moved around on their hind legs.

The footprints are in a limestone quarry in Oxfordshire, England, that's home to some of the best-preserved dinosaur "trackways" in the world. Some sets of prints in the area extend for 150 yards (180 meters).

One trackway preserves the three-toed prints of a megalosaurus, which looked like a mid-size version of Tyrannosaurus rex. Both were theropods -- carnivorous dinosaurs that walked mainly on two legs instead of four.

Researchers Julia Day of the University of Cambridge and colleagues who studied the prints found that a portion of the trackway shows the pattern changing remarkably. Most the prints appeared to have been made at a walking pace -- the stride is short, the toes are angled in, and the stance is what's called wide gauge, meaning the feet are spaced out wide from each other.

But in a short section of the trackway the pattern changes to a longer stride with the dinosaur placing one foot directly in front of the other, toes pointing more forward, indicating it was running.

Based on what researchers know about megalosaurus, the size of the prints, and the length of the stride, the scientists calculate the dinosaur walked at a speed of just over 4 mph (7 km/h) and ran at a top speed of just under 20 mph (30 km/h). They say it is unclear how long it could sustain a running pace.

The researchers say trackway evidence of a running dinosaur is very rare. Analysis of the tracks might yield a bonanza of information that they could use to test out all kinds of biomechanical theories about how the big animals moved, and how theropods evolved.

The research is published in this week's edition of the British journal Nature.


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