Underwater tracks reveal that dinosaurs could swim

Underwater tracks reveal that dinosaurs could swim
By Steve Connor, Science Editor
Published: 25 May 2007
Independent UK

Dinosaurs were good swimmers, according to scientists who have found the first hard evidence to show that these land giants took to moving through water.

Palaeontologists have discovered a set of underwater tracks made by the hind limbs of a bipedal dinosaur as it swam against a strong current. "This is the first time that a full, underwater trackway - a full sequence of swimming - has been preserved for a dinosaur," said Loic Costeur, of the University of Nantes. "The dinosaur swam with alternating movements of the two hind limbs, a pelvic paddle swimming motion.

"It is a swimming style of amplified walking with movements similar to those used by modern bipeds, including aquatic birds."

The trackway was discovered at a well-known site for dinosaur fossils at La Virgen del Campo in the Cameros Basin of northern Spain. The find is reported in the journal Geology.

The scratches in the sandstone were barely concealed by topsoil and they have been dated to about 120 million years ago - the Cretaceous period when dinosaurs dominated the land.

The trackway consists of six asymmetric pairs of between two and three scratch marks, preserved in a layer of sandstone formed from sediments. Each set of marks is about 50cm in length, 15cm wide and spaced in such a way that they suggest a stride of 2.4m-2.7m.

Dr Costeur said the scratches indicated that the large animal walked on its hind legs and had a clawed foot with three toes. "The trackway is quite amazing," he said. "It cannot have been made by a walking dinosaur because the scratch marks are quite delicate with long grooves made in the sediment indicating a large, swimming animal. They are so delicate that they could only be made by animal whose body was supported by water. There were also ripple marks in the sandstone indicating that the water was up to 3m deep."

Scientists have previously found underwater tracks made by large dinosaurs as they walked through water but the latest discovery is the first to show that some dinosaurs were capable ofswimming against a strong current.

"The trackway at La Virgen del Campo opens the door to several new areas of research," said Dr Costeur. "New biomechanical modelling will increase our understanding of dinosaur physiology and physical capabilities, as well as our view of the ecological niches in which they lived,"