Dinosaur dog-paddle

Over 100 million years ago, in what is now China's Szechuan Province, dinosaurs of both the 2-legged variety (therapods) and the 4-legged variety (sauropods) travelled a riverbed like a superhighway. During the dry cycle they lumbered, but during the wet cycle they swam. Working with an international research team, University of Alberta graduate student Scott Persons examined unusual claw marks left on the river bottom that indicate a coordinated, left-right, left-right progression over a distance of 15m. Says Persons, "What we have are scratches left by the tips of a two-legged dinosaur's feet. The dinosaur's claw marks show it was swimming along in this river and just its tippy toes were touching bottom." It is the strongest evidence yet that a dinosaur – in this case a bipedal carnivore that stood roughly 1m tall at the hip – could forge moderately deep bodies of water with coordinated leg movements. "Swimming could be the born ability of dinosaurs, just like dogs," adds study participant Martin Lockley of Denver's Dinosaur Tracks Museum.

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