Sep 27, 2013 09:14 AM EDT By Staff Reporter, UniversityHerald Reporter

Scientists from the University of Alaska Museum of the North discovered thousands of fossilized dinosaur footprints along the Yukon River.

"This is the kind of discovery you would have expected in the Lower 48 [states] a hundred years ago," said Pat Druckenmiller, University of Alaska Museum of the North earth sciences curator, in an official statement.

The footprints belonged to a variety of dinosaurs-big and small, meat and plant eaters.

The discovery happened when the team embarked on a 500-mile (800 kilometers) journey down the Tanana and Yukon rivers this summer. They brought back 2,000 pounds (900 kilograms) of dinosaur footprint fossils.

"We found dinosaur footprints by the scores on literally every outcrop we stopped at," expedition researcher Paul McCarthy, of the University of Alaska Fairbanks, said. "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."

Druckenmiller said that the trip resulted in an 'evidence of an extinct ecosystem we never knew existed.'

According to Discovery, the footprints are believed to be at least 25 million years older than the ones unearthed in Alaska's Denali National Park, which are estimated to be up to 70 million years old.

Surprisingly, the fossilized dinosaur footprints found in Alaska protruded from the rocks instead of sunken inwards.

Druckenmiller said that the reason why they have been ignored until now is because they're in 'natural casts,' meaning, the sand must have filled in the actual foot trail after the dinosaurs stepped in mud.

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

"If there's a big storm and the footprint is covered in clay blown from the hillside, it will cover the footprint," Mark Norell, the head of paleontology at the American Museum of Natural History told ABC News. After it hardens over millions of years, the clay molding ends up capturing what the foot itself looked like. "It's like you're seeing the animal's foot while it was alive."

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