for National Geographic News
Predatory dinosaurs such as the mighty Tyrannosaurus rex could swim, say scientists who claim they have found definitive proof of the behavior.
The evidence, they say, is odd scuff marks found in Cretaceous-era rock in northern Spain's Cameros Basin.
The Cretaceous period lasted from 145.5 million to 65.5 million years ago.
The tracks, which are 50 feet long (15 meters long) and contain 12 prints, suggest that a large animal was scrabbling at the bottom of a 10-foot-deep (3-meter-deep) lake with a swimming, not wading, motion.
The marks were likely left more than one hundred million years ago at the well-preserved La Virgen del Campo site, where scientists have also unearthed more than 10,000 other fossil footprints.
Ripples in the stone show that the dinosaur—possibly a T. rex—was fighting a current, trying not to drift sideways.
The tracks are distinct from known swimmers of the period, such as turtles or crocodiles, and indicate that the animal was a theropod—a carnivore that walked upright.
Theropods include T. rex and numerous smaller dinosaurs, including the velociraptors of Jurassic Park fame.
Tracking a Swim
Scientists have long known that such dinosaurs could wade.
(See related: "Dino-Era Lizard Is Missing Link to Swimming Reptiles, Experts Say" [November 21, 2005].)
But proving they could also swim has been difficult, because an animal that is totally afloat leaves no tracks. So the only way to prove that they could swim is to find footprints left by a dinosaur in contact with the bottom.
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