Yukon River dino fossils broaden understanding of Alaska prehistory

University of Alaska researchers collected 2,000 pounds of fossils on the trip

A dinosaur site newly discovered along the banks of the Yukon River has provided scientists with tons of fossils, along with a more complete profile of the creatures that roamed what is now Alaska millions of years ago.


Pat Druckenmiller, University of Alaska Fairbanks Museum of the North earth sciences curator, recently returned from a two-week, 500-mile expedition down the Yukon River that yielded no less than 2,000 pounds of fossilized dinosaur footprints, he said. The tracks are 90 to 100 million years old, significantly older than other dinosaur fossils found in Alaska. The oldest fossils previously found in the state are about 70 million years old, he said.

“Most of what we know about in Alaska is a tiny window of time 70 million years ago,” Druckenmiller said. “This find pushes back the time by millions of years.”

In the more recent past, Alaska has become a hot spot for finding dinosaur fossils, he said. But the abundance of fossils found along the river made this expedition remarkable.

“It was really exciting to realize we weren’t just finding a few isolated fossils, but a whole new area for dinosaur research we didn’t know about a year ago,” Druckenmiller said. “That’s something you don’t get to do every day. That’s pretty uncommon, even for Alaska.”

The prints were large and small, made by carnivores and herbivores, he said. The most common at the site were left behind by Ankylosaurus: squat, armored plant-eaters with “really distinctive kinds of feet.” This is a type of dinosaur not commonly represented in Alaska’s fossils, Druckenmiller said.

The discoveries made on the trip are only “the tip of the iceberg,” he said. The team of 12 student and faculty researchers found the footprints — more accurately, natural casts of footprints — on every outcrop along the river between Ruby and Kaltag. The group floated the river in four small boats and moved camp every night for two weeks.

“We were only able to collect a tiny fraction of what was really out there,” Druckenmiller said. “More trips out will probably reveal new types of dinosaurs we don’t know existed in this state yet.”

The most common places to find dinosaur fossils in Alaska are the North Slope and Denali National Park, Druckenmiller said. You won’t find any in Southeast Alaska, he said. During the time of the dinosaurs, what is now Southeast was still inching its way up the west coast of the Americas, propelled by sea floor spreading.

Tongass National Forest geologist Jim Baichtal said the closest Southeast comes to dino fossils of its own are those belonging to ancient marine reptiles. These are as old as 225 million years, predating the state’s dinosaur fossils by more than 100 million years.

“A lot happened between these wee beasties and Pat’s wee beasties,” Baichtal said.

These reptiles range in size from “not much over a meter to one that would be as big as, if not bigger than, a killer whale,” Baichtal said. Remnants of three or four different species have been found near Kake, in Ketchikan and on Admiralty Island, among other locations. Research on these prehistoric swimmers began in 2003, he said.

Baichtal and other researchers have also found fossils of marine invertebrates that coexisted with the reptiles.

“We have a pretty clear picture of what the environment looked like that these things were swimming through,” he said.

Digs are ongoing in Southeast, Baichtal said. In fact, he, Druckenmiller and another scientist discovered two new fossil beds in the region this summer. Baichtal is holding on to the fossils until he can ship them up to Druckenmiller to display in the Museum of the North.

“I have a pile of them in my garage right now,” Baichtal said.

In the coming years of the Yukon River project, Druckenmiller wants to involve communities along the way by developing outreach programs.

“We’ve been trying to let people in local communities know about cool things in their backyard,” he said. “My goal is that over time this will be an exciting thing not just for science or research but for communities along the river.”

Another research expedition down the river will happen next summer, Druckenmiller said.

“A site like this, it could keep you busy for a really long time,” he said.

• Contact reporter Katie Moritz at 523-2294 or at katherine.moritz@juneauempire.com.


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