Doggy Paddling Dino Discovered

by ScienceDave | May 24, 2007 at 08:35 pm

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Next time you and your sweetheart crawl into your time machine and zip back to the Cretaceous for a late-night skinny dip in the ol' swimming hole, be sure to watch your back.

Scientists from Spain have unearthed the most compelling evidence to date for swimming theropods (a group that includes the infamous T. rex and velociraptor). The tracks were discovered in the La Virgen del Campo track site in northern Spain. This particular site has gained attention for preserving tracks of land dwelling species of "terrible lizards".

With three telltale toemarks on each print, the tracks clearly belonged to a major group of bipedal, carnivorous dinosaurs called theropods. But the tracks themselves were different. When theropods walk on land, they typically leave claw marks and an imprint of the foot itself. The lack of the footprint suggested that this animal was not supporting its weight. A sedimentologist on the team confirmed that ripple marks in the stone had been created by currents in water 3.2 meters deep.

The ripple marks in the sediment suggest the formidable beast was up against a strong current, but was still able to stay on course. What would a swimming theropod look like if, for example, you neglected to heed my aforementioned warning?

With its toes just touching bottom, the animal probably had its head and neck exposed as well as its rigid tail. Because theropod tails were stiffened with ligaments, the animals could not have used them for propulsion, as crocodiles do. "This thing was doing a sort of dog paddle only using its hind limbs," Henderson [curator of dinosaurs at the Royal Tyrell Museum of Paleontology in Drumheller] concludes.