某些恐龙可能是游泳健将

A University of Alberta researcher has identified some of the strongest evidence ever found that dinosaurs could paddle long distances. Working together with an international research team, U of A graduate student Scott Persons examined unusual claw marks left on a river bottom in China that is known to have been a major travel-way for dinosaurs.

Alongside easily identified fossilized footprints of many Cretaceous era animals including giant long neck dinosaur's researchers found a series of claw marks that Persons says indicates a coordinated, left-right, left-right progression.

"What we have are scratches left by the tips of a two-legged dinosaur's feet," said Persons. "The dinosaur's claw marks show it was swimming along in this river and just its tippy（不安定的） toes were touching bottom."

The claw marks cover a distance of 15 meters which the researchers say is evidence of a dinosaur's ability to swim with coordinated leg movements. The tracks were made by carnivorous theropod（兽脚类的肉食恐龙） dinosaur that is estimated to have stood roughly 1 meter at the hip.

Fossilized rippling and evidence of mud cracks indicate that over 100 million years ago the river, in what is now China's Szechuan Province, went through dry and wet cycles. The river bed, which Persons describes as a "dinosaur super-highway" has yielded plenty of full foot prints of other theropods and gigantic four-legged sauropods（蜥脚类动物）.

With just claw scratches on the river bottom to go with, Persons says the exact identity of the paddling dinosaur can't be determined, but he suspects it could have been an early tyrannosaur or a Sinocalliopteryx. Both species of predators were known to have been in that area of China.