University of Alaska Fairbanks

A couple of summers ago, David Tomeo was exploring a creekbed in Denali National Park, preparing for a field seminar on the park’s dinosaurs he would help lead a few weeks later. With a trained eye for the impressions dinosaurs pressed into mud millions of years ago, Tomeo walked to a large boulder in the middle of a landslide.

“Right in the middle of it, a four-toed track stood out,” said Tomeo, program director for Alaska Geographic at the Murie Science and Learning Center in Denali Park.

Tomeo snapped a picture of the track and sent it to Tony Fiorillo, a dinosaur hunter from the Museum of Nature and Science in Dallas who often travels to Alaska.

Fiorillo was intrigued. The track looked like that of a therizinosaur, a tall, feathered meat-eater with sickle-like claws that extended a few feet from the three fingers of each hand.

“Therizinosaurs are totally weird,” Fiorillo said. “These guys are unlike any predatory dinosaur you’ve ever seen. From head to feet, they are different.” 

Fiorillo later visited the site with Tomeo and conferred with other dinosaur experts. Therizinosaurs had been recorded in Mongolia and paleontologists found the bones of a closely related creature in Utah, but Fiorillo had never seen the evidence of one himself.

After removing his doubts about the track, a process that took several years, Fiorillo recently co-authored a paper in which he reported on the first record of a therizinosaur from Alaska.

The eclectic therizinosaur, which walked Denali about 70 million years ago, probably made it to Alaska via the Bering Land Bridge. The dinosaur joins the ranks of discovered prehistoric creatures that seemed to have lived in great numbers in a warmer (but just as dark in winter) Alaska of long ago.

Artist Nobu Tamura sketched this therizinosaur.