Tracks of Australia's Stampeding Dinosaurs are Swimming Marks: Study

Researchers have discovered that the fossilized tracks of a dinosaur stampede in Australia were actually tracks made by swimming animals rather than by running ones.

Thousands of small dinosaur tracks were found at Lark Quarry Conservation Park, central-western Queensland, and recorded as the world's only dinosaur stampede. The tracks, dating back to 95-98 million years ago, are preserved in a shallow river that was once part of a vast, forested floodplain.

Earlier studies construed the tracks as evidence showing small dinosaurs escaping the clutches of a large theropod. But a new study by researcher Anthony Romilio from the University of Queensland found that the large tracks, which were thought to be of the theropod, actually belong to a plant-eating dinosaur called Muttaburrasaurus. This could mean the previous theory suggesting that the dinosaurs were fleeing from a large predator might need a rethink, according to a report in LiveScience.

For the study, Romilio and his colleagues analyzed the tracks using three-dimensional computer modeling. They found that the tracks were made by short-toed dinosaurs and not by long-toed ones as previously thought. They suggested that these tracks could not have been made by running or walking animals, as they could not find a flatter impression of the dinosaurs' foot preserved in the sediment.

"Many of the tracks are nothing more than elongated grooves, and probably formed when the claws of swimming dinosaurs scratched the river bottom," Romilio said in a statement.

"Some of the more unusual tracks include 'tippy-toe' traces - this is where fully buoyed dinosaurs made deep, near vertical scratch marks with their toes as they propelled themselves through the water."

The swimming dinosaur tracks belong to small, two-legged herbivorous dinosaurs known as ornithopods. Using the tracks, researchers interpreted that the dinosaurs were moving downstream, with the current of the river to help in their movements. The tracks also revealed that the water levels fluctuated, suggesting that the marks were formed over several days of dinosaur migration.

The findings of the study are published in the January issue of the Journal of Vertebrate Paleontology.