Definitive Evidence Found Of A Swimming Dinosaur

["Richard W. Travsky" <rtravsky@uwyo.edu>]

http://www.sciencedaily.com/releases/2007/05/070524091023.htm

An extraordinary underwater trackway with 12 consecutive prints provides 
the most compelling evidence to-date that some dinosaurs were swimmers. 
The 15-meter-long trackway, located in La Virgen del Campo track site in 
Spain's Cameros Basin, contains the first long and continuous record of 
swimming by a non-avian therapod dinosaur.

A team led by Rubn Ezquerra, Fundacin Patrimonio Paleontolgico de La 
Rioja, La Rioja, Spain, discovered the prints in an area long known for 
its abundance of terrestrial dinosaur trackways dating from the early 
Cretaceous 125 million years ago. The team's findings are reported in the 
June issue of GEOLOGY, published by the Geological Society of America.

The trackway consists of 6 asymmetrical pairs of 2-3 scratch marks each. 
Each set of scratch marks, preserved in a layer of sandstone, averages 
approximately 50 centimeters in length and 15 centimeters wide. The 
spacing between them suggests an underwater stride of 243-271 centimeters.

According to co-author Loic Costeur, Laboratoire de Plantologie et 
Godynamique de Nantes, Universit de Nantes, France, the S-shaped prints 
paint a picture of a large floating animal clawing the sediment as it swam 
in approximately 3.2 meters of water. Ripple marks on the surface of the 
site indicate the dinosaur was swimming against a current, struggling to 
maintain a straight path.

"The dinosaur swam with alternating movements of the two hind limbs, a 
pelvic paddle swimming motion," said Costeur. "It is a swimming style of 
amplified walking with movements similar to those used by modern bipeds, 
including aquatic birds."

The question of whether dinosaurs could swim has been researched for 
years. Until now, however, very little hard evidence existed documenting 
the behavior. Several earlier discoveries were later found to have been 
produced on dry ground or categorized as ghost traces, possible 
undertracks preserved in lower layers of sediment.
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