Real-life Jurassic Park! Thousands of fossilised dinosaur footprints have been discovered along the rocky banks of Alaska's Yukon River.
The large and small footprints may have just scratched the surface of a major new dinosaur site nearly inside the Arctic Circle.
"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," said Pat Druckenmiller from the University of Alaska Museum of the North.
In July 2013, researchers set off in boats for a 805km journey down the Tanana and Yukon rivers. Co-discoverer Kevin May, operations manager at the UA Museum of the North, says the goal was to explore as many beaches as possible for evidence of dinosaurs.
"Based on what we know about the geology along the Yukon River, the rocks exposed downriver from Ruby suggested they might be a good place to find dinosaurs," said May.
They found much more than they expected - dinosaur footprints big and small, from both meat- and plant-eaters.
"We found a great diversity of dinosaur types, evidence of an extinct ecosystem we never knew existed," Druckenmiller said.
"We found dinosaur footprints by the scores on literally every outcrop we stopped at," Paul McCarthy from the University of Alaska Fairbanks.
"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 says the dinosaur footprint-bearing rocks from along the Yukon River are probably about 25-30 million years older than what's been found in Denali Park.
"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," McCarthy said.
Druckenmiller said that one of the reasons the Yukon River dinosaur tracks may have gone undiscovered for so long is due to their method of preservation - they are "natural casts" formed when sand filled in the actual footprint after the dinosaur stepped in mud.
The discovery is significant in that the Yukon River fossils are geologically older than other major sites in the state and that they preserve a record of dinosaurs previously unknown in the state.
