October 18, 2005

Evidence of Swimming Dinosaur Found

CHEYENNE, Wyo. -- Researchers have found tracks of a previously unknown, two-legged swimming dinosaur with birdlike characteristics in northern Wyoming and are looking for bones and other remains in order further identify and name it.

"It was about the size of an ostrich, and it was a meat-eater," said Debra Mickelson, a University of Colorado graduate student in geological sciences. "The tracks suggest it waded along the shoreline and swam offshore, perhaps to feed on fish or carrion."

The tracks indicate a dinosaur that was about 6 feet tall and lived about 165 million years ago along an ancient inland sea, Mickelson said in a university news release.

"The swimming dinosaur had four limbs and it walked on its hind legs, which each had three toes," she said. "The tracks show how it became more buoyant as it waded into deeper water - the full footprints gradually become half-footprints and then only claw marks."

Mickelson said research so far by herself and others supports the "conclusion that the dinosaurs were intentionally swimming out to sea, perhaps to feed."

Mickelson was presenting her findings at the Geological Society of America's annual meeting this week in Salt Lake City and was unavailable for comment.

The finding would be significant because so far no one has been able to prove that aquatic dinosaurs existed, Joanna Wright, assistant professor of geology at the University of Colorado-Denver, said Monday. There were swimming reptiles that are now extinct, Wright said.

Wright said she has not reviewed what Mickelson and other researchers involved have found, but she would be interested in seeing photos of the tracks.

The news has perked up the ears of some prominent paleontologists.

"I'm not a trackway specialist, but it sounds pretty cool to me," Jack Horner, curator of paleontology at the Museum of the Rockies and one of the nation's leading fossil hunters, said by telephone from Bozeman, Mont.

Horner said he was unaware of any previously discovered dinosaur tracks "where it actually goes from land into the water."

The unique tracks were found at a number of sites in northern Wyoming, including the Bighorn Canyon National Recreation Area along the Wyoming-Montana state line.

The tracks are embedded in a layer of rock known as the Middle Jurassic Bajocian Gypsum Spring Formation. Geologists believe an inland sea covered Wyoming and a large area of the western United States during the Jurassic period from about 157 million to 165 million years ago.

Mickelson said the unidentified dinosaur tracks are found among tracks left by many animals, including ancient crocodiles and marine worms, and are of different sizes.

The tracks suggest that the dinosaur traveled in packs and exhibited some variation in overall size, she said.

Mickelson collaborated her findings with researchers from CU-Boulder, Indiana University, Dartmouth College, Tennessee Technological University and the University of Massachusetts.


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