Major Dinosaur Fossil Find in Alaska Shows Great Diversity

A major site of dinosaur fossils has been found along the Yukon River in Alaska.

Researchers from University of Alaska Museum of the North found a wealth of fossilized dinosaur footprints along several riverbanks sites in Alaska.

The paleontologists behind the expedition heralded the find as a once-in-a-lifetime occurrence.

"There aren't many places left in the world where paleontologists can just go out and find thousands of dinosaur footprints. This is the kind of discovery you would have expected in the Lower 48 a hundred years ago," the museum's Earth Sciences Curator Pat Druckenmiller said in a statement.

It is still unclear what type of dinosaurs made the footprints.

The researchers embarked on a 500-mile river journey in July 2013 with the goal to explore as many beaches as possible for evidence of dinosaurs. The results were unexpected, the researchers said.

"We found a great diversity of dinosaur types," Druckenmiller said, "evidence of an extinct ecosystem we never knew existed."

Paul McCarthy, from the Department of Geology and Geophysics at the University of Alaska Fairbanks, said they found dinosaur footprints "by the scores" at every outcrop they stopped at.

"I've seen dinosaur footprints in Alaska now in rocks from southwest Alaska, the North Slope, and Denali National Park in the Interior, but there aren't many places where footprints occur in such abundance," McCarthy said.

McCarthy said the footprints found in the rocks are between 25 million and 30 million years older than dinosaur remains found in Denali Park.

"It took several years of dedicated looking before the first footprint was discovered in Denali in 2005, but since that time dozens of tracks of dinosaurs and birds have been found," McCarthy said. "In contrast, the tracks were so abundant along the Yukon River that we could find and collect as many as 50 specimens in as little as ten minutes."

Druckenmiller said one reason it took so long before the footprints were discovered is because they are not the negative impressions, but "natural casts" formed when sand filled the actual footprint after the dinosaur stepped in mud.

"These are not negative impressions," Druckenmiller said. "Rather they stick out from the rock and sometimes look like blobs with toes."

The researchers say there is still much work to be done before they fully understand the fossil find. They are coordinating with native groups and villagers for future expeditions to the region.