Swimmer sauropod dinosaurs walked on earth: Study

An international team of scientists says the unusual dinosaur tracks found in northern China might have been by the four-legged sauropod dinosaurs.

Previous studies of such track ways have suggested that the dinosaurs, which were far too big to walk on their hind legs, might have been swimming.

The scientists from China University of Geosciences in Beijing, including palaeontologists from the University of Bristol suggested that trackways fossil trackways from Gansu Province in northern China, in which only the front or hind feet are imprinted into the sediment, were produced by walking, not swimming animals.

Published in journal Scientific Reports, the new study said the tracks, dating from the Lower Cretaceous, over 120 million years ago, are roughly circular and with a clear set of four or five claw marks at the front.

These prints perfectly match the feet of medium-sized sauropod dinosaurs, massive long-necked, plant-eating dinosaurs such as Brontosaurus and Titanosaurus.

"Nobody would say these huge dinosaurs could stagger along on their hind legs alone - they would fall over. However, we can prove they were walking because the prints are the same as in more usual tracks consisting of all four feet, its just that here, we do not see the hand prints," lead author Lida Xing said.

"If they had been swimming, with the hind legs dangling down, some of the foot prints would be scratch marks, as the foot scrabbled backwards," Xinga added.

The study said that most of the animal's weight was towards the rear, and so the hind-feet pressed deeper. The front feet, on the other hand, did not apply enough pressure to make a lasting mark.