Land Dinos Swam, Footprints Show

May 24, 2007 — The first definitive evidence of a dinosaur swimming has been discovered by paleontologists working at the site of a long-lost lake in Spain's Cameros Basin.

The evidence is in the form of ancient curved claw marks preserved in sandstone. The 125-million-year-old scratches were almost certainly made by a large animal floating in the water and accidentally grazing the sandy bottom with its toes, or claws, as it swam.

"It's a bit like elephants or bears can do today," said paleontologist Loic Costeur of the Universite de Nantes, France. In other words, the dinosaur that made the marks was a land animal crossing through the water, he explained.

Costeur is a coauthor of a report in the June issue of the journal Geology. The team that made the discovery was led by Ruben Ezquerra of Spain's Fundacion Patrimonio Paleontologico de La Rioja.

The tracks themselves cover a distance of about 50 feet (15 meters) and consist of six symmetrical pairs, each with two or three scratches. The right-hand tracks are clearly pushing more directly outward, as if the dinosaur was fighting a current coming from the front and to the left.

Bolstering the argument that the marks were created by a dinosaur is the stride distance between the individual tracks — about eight feet (2.5 meters) — which suggest a large animal.

Also compelling is the fact that the surrounding area is packed with thousands of walking dinosaur prints that are part of the La Virgen del Campo track site, Costeur explained to Discovery News.

Although it's impossible to say for certain what kind of dinosaur made the tracks, said Costeur, the allosaur is a candidate, since it was common in the Cameros Basin in the early part of the Cretaceous — when the basin was a very large lake.

"The place is full of walking theropod dinosaur footprints," he said.

"It doesn't surprise me at all that theropod dinosaurs had the ability to swim," said dinosaur track specialist Brent Breithaupt, curator and director of the Geological Museum at the University of Wyoming in Laramie. "What does surprise me is that you'd find evidence of this."

And unlike some possible swimming dino tracks that Breithaupt has heard of here and there in the Rocky Mountains, the new discovery is more than a single track.

"It's wonderful that it is a track-way and not an individual track," Breithaupt told Discovery News. Without many tracks, it's impossible to sort out what the creature was doing.

The Lake Cameros swimming track is so good, said Breithaupt, that it could very well serve as an archetype for paleontologists looking for such tracks elsewhere.