‘We were freaking out’ – Scientists Explore Dinosaur Colosseum

Scientists from the University of Alaska Fairbanks have discovered and documented the largest known dinosaur tracking site in Alaska. Located in Denali National Park and Preserve, this gorgeous site has been dubbed “The Colosseum” by experts.

Spanning the equivalent of one and a half football fields, the Colosseum is an impressive collection of rock strata, each preserving a wealth of dinosaur footprints. This site provides a comprehensive historical account of the various dinosaurs classify which thrived in what is now known as the Alaskan interior, approximately 70 million years ago. The researchers’ findings and detailed descriptions of the Coliseum are presented in a research paper recently published in the journal Historical Biology.

“It’s not just one level of rock with traces,” said Dustin Stewart, lead author of the paper and a former UAF graduate student who published the paper as part of his master’s thesis. “It’s a sequence through time. So far, Denali has had other known tracking sites, but nothing of this magnitude.”

At first glance, the site seems unremarkable in the context of the park’s vast landscape: just a layered rock outcropping that rises 20 stories from its base.

“When our colleagues first visited the site, they saw a dinosaur track at the base of this massive cliff,” said Pat Druckenmiller, senior author of the paper and director of the University of Alaska Museum of the North. “When we first got out there, we didn’t see much either.”

Stewart recalls being frustrated at first when he approached the site at the end of a seven-hour trek. Then dusk approached and the team took another look.

Track of a large, meat-eating dinosaur, likely from Tyrannosaurus. The image was made by taking multiple photos from different angles to produce a 3D rendering of the track, highlighted by colours. Credit: Photo by Dustin Stewart

“When the sun is totally skewed with those beds,” he said, “it blows.” “Immediately we were all freaked out, and then Pat said, ‘Get your camera.’ We were freaking out.”

Late chalky Period, the cliffs that make up the Colosseum were deposits on flat ground near what was likely a watering hole in a large flood plain. When the Earth’s tectonic plates collided to form the Alaskan Range, the previously flat land flexed and tilted vertically, revealing slopes dotted with tracks.

The tracks are a mixture of hardened impressions in ancient clay and track molds created when sediment filled the tracks and then hardened.

“They’re beautiful,” Druckenmiller said. “You can see the shape of the toes and the texture of the skin.”

In addition to dinosaur tracks, the research team found fossilized plants, pollen, and evidence of freshwater oysters and invertebrates.

“All of these little clues have pulled together what the environment looks like as a whole,” Stewart said.

Close-up on one of the walls showing several depressions of the hadrosaur’s footprints. The ice ax in the lower left of the frame is about 3 feet long, for scale sake. Credit: Photo by Patrick Druckenmiller

He said the area was part of a large river system, with ponds and lakes nearby. The climate in the region was much warmer than it is today, much like the Pacific Northwest. There were coniferous and deciduous trees, a few ferns and horsetails.

Based on the tracks, a variety of juvenile to adult dinosaurs have frequented the area over the millennia. The most common were the large, horn-beaked, plant-eating dinosaurs. The team also documented rare predators, including raptors and tyrannosaurs, as well as small wading birds.

Every year, thousands of people visit Denali National Park and Preserve, Druckenmiller said, to experience the scenic landscape and environment. “It is amazing to know that about 70 million years ago, Denali was equally impressive for its flora and fauna.

“It was jungle,” he said, “and it was teeming with dinosaurs.” “There was a dinosaur running around Denali that was many times the size of the largest brown bear out there today. There were birds of prey. There were flying reptiles. There were birds. It was an amazing ecosystem.”

Denny Capps, a geologist with the park, said preserving fossil sites like the amphitheater is an important part of the National Park Service’s mission.

“On the one hand, we must protect world-class excavation sites such as the Colosseum from disturbance and theft,” he said. “On the other hand, we encourage visitors to explore fossils in their own geological context to better understand the evolution of landscapes and ecosystems through time, while leaving them undisturbed for others to appreciate.”

Druckenmiller plans to continue collaborating with the National Park Service to study the Coliseum and other trail sites.

“Our research on the track in the park complements our work on dinosaur bones that we collect in northern Alaska, along the Colville River,” Druckenmiller said. Denali National Preserve is a world-class area for dinosaur tracks. There’s still a lifetime of exploration to do, and I can’t help but wonder what other surprises await.”

Reference: “Vertebrate Biology and Paleoecological Associations of the Largest Known Alaskan Dinosaur Tracking Site in the Cantwell (Maastrichttan) Cretaceous Formation of Denali National Park and Preserve” by Dustin G. Stewart, Patrick S. Druckenmiller, Gregory M. Erickson, Jeff A. Benovitz, Denny M. Capps , Cassandra L. Knight, Kevin C. May and Paul J. McCarthy, July 27, 2023, Historical Biology.
DOI: 10.1080 / 08912963.2023.2221267

The study was funded by the National Science Foundation and the National Park Service.