Dinosaurs Could Swim

Q: Your article about swimming ostriches got me wondering. Could Tyrannosaurus Rex swim? You mentioned they had light bones, sort of like birds.
Greg, La Mirada, California

A: It's a warm, muggy day about 125 million years ago (early Cretaceous period) when dinosaurs roamed the land and flew the skies of what is now northern Spain.

The air is full of squawks and songs of dinosaurs. Birds add their calls to the cacophony, as they flit among tall cyads, which crowd the shore of a vast lake.

A pack of large, swift Utahraptor dinosaurs mill on the shore, sniffing to catch scent of likely prey. A female catches a faint whiff of a herd of lumbering Iguanodons, and darts after them. Four follow, but the fifth gets distracted. Ute, a young 20-foot (6-m) male nearest the lake, sees a huge pterosaur, diving low right at him. Ute leaps to snag her with curved talons, but misses. The pterosaur squawks her outrage, tilts her wings, and soars out to an island breeding ground.

Ute roars, bounds after her and splashes into the lake, upright on his two powerful hind legs. He soon realizes she's outdistancing him, but young and predator-curious, he follows anyway. At first, he wades, but, as the ground drops away, water covers more of his body, buoying him, so his feet barely touch. Gigantic claws on his hind feet gouge deep tracks in the mud. Then he can touch no more. He's swimming. The offshore current catches him, and tends to sweep him left. Ute crabs right, and trails the flyer on a direct path to the island. He swims steadily, paddling with his hind legs like a duck. In about a half hour, Ute makes land.

It's a dino's dream! Thousands of pterosaurs roosting, waiting to be harvested.

This fictional scenario is based on scientific findings. A team of paleontologists, lead by Rubén Ezquerra, found a set of twelve fossil claw prints forming a 50-foot (15-m) long trackway in the solidified offshore sediment of a former large lake in what is now northern Spain. The team dated the tracks to the early Cretaceous period, about 125 million years ago.

"The tracks strongly suggest a floating theropod [a bipedal, lizard-hipped, carnivorous dinosaur], clawing the sediment as it swam in at most three meters (ten feet) of water," emails paleontologist Loïc Costeur of Laboratoire de Planétologie et Géodynamique de Nantes, Université de Nantes, France, one of the team. "The dinosaur swam with alternating movements of the two hind limbs, a pelvic paddle motion, similar to those used by modern bipeds, including aquatic birds."

As in my scenario, the dinosaur crabbed right to counteract a "leftward water current", and maintained his chosen direction. In an article published in the June 2007 issue of Geology, the team concluded, the evidence "persuasively demonstrates that some non-avian theropod dinosaur were swimmers." Furthermore, "they may well have occupied hitherto unsuspected ecological niches."

Further Reading:

Ostriches swim! WonderQuest

Could a dinosaur scratch when he itched, and did he itch? WonderQuest

Did dinosaurs live in Antarctica? WonderQuest

Were non-avian theropod dinosaurs able to swim? Supportive evidence from an Early Cretaceous trackway, Cameros Basin (La Rioja, Spain), by Rubén Ezquerra, Stéfan Doublet, Loïc Costeur, Felix Pérez-Lorente, Geology, June 2007, v. 35, no. 6, p. 507-510.

U of Colorado researcher identifies tracks of swimming dinosaur in Wyoming, University of Colorado

The 'inflatable' dinosaurs of the Mesozoic by Donald Henderson, University of Calgary, NSERC

(Answered Sep. 10, 2007)