University of Alberta graduate student Scott Persons, working with an international research team, says the evidence is to be found in unusual claw marks left on a river bottom in China known to have been a major travel-way for dinosaurs.
A series of fossilized claw marks preserved on the river bottom indicates a coordinated left-right, left-right progression, Persons said in a U of A release Monday.
"What we have are scratches left by the tips of a two-legged dinosaur's feet," he said. "The dinosaur's claw marks show it was swimming along in this river and just its tippy toes were touching bottom."
Covering almost 50 feet, the claw marks are evidence of a dinosaur's ability to swim with coordinated leg movements, researchers said.
The tracks were made by carnivorous theropod dinosaur estimated to have stood roughly 3 feet high at the hip, they said.
With just claw scratches on the river bottom as evidence, Persons said the exact identity of the swimming dinosaur can't be determined although he suspects it could have been an early tyrannosaur, a species known to have been in that area of China, now the country's Szechuan province.