Denali Dinos: Ancient Bones Are First of Their Kind in National Park
Undergraduate paleontology students Thomas Sniezak, of the University of Alaska, and Nick Freymueller, of the University of New Mexico, create a mold, or peel, of the original track for further study.

Credit: Pat Druckenmiller

Alaska's majestic Denali National Park is home to North America's tallest mountain and a wide array of wild animals, including moose, wolves and grizzly bears. But now, scientists have concrete evidence that the park was once home to an entirely different set of creatures: dinosaurs. 

Researchers found the fossilized bones of what they think are dinosaurs during a July 2016 expedition that included paleontologists from the University of Alaska Fairbanks (UAF) and the National Park Service, according to an online announcement that was made Tuesday (Oct. 18). The group also discovered several new dinosaur trackways — fossilized impressions of footprints left by dinosaurs that once walked though mud that later turned into rock.

"This marks the beginning of a multiyear project to locate, document and study dinosaur fossils in Denali National Park," Pat Druckenmiller, the leader of the collaborative dinosaur project and a curator of earth sciences at the University of Alaska Museum of the North, said in a statement. [See Photos of the Dinosaur Discovery in Denali]

They found a total of four bone fragments — the largest of which is just a few inches long — that seem to be parts of larger bones that belonged to a big beast, and not to a smaller mammal, bird or even a flying reptile, the researchers said. The specimens also resembled other plant-eating dinosaur bones found in other parts of Alaska, the researchers said.

The microstructure of one of the specimens — a large fragment of spongy bone — indicates that it isn't from a crocodile or slow-growing, cold-blooded (also known as ectothermic) animal, the researchers said. And a preliminary analysis of the shape and structure of another of the specimens, an ossified tendon, indicates that the fibrous connective tissue may have belonged to a large ornithopod dinosaur, likely a duck-billed dinosaur, Druckenmiller said.

An extremely well-preserved meat-eating dinosaur footprint in Denali, clearly showing the fleshy pads of skin, claw impressions and skin texture.
An extremely well-preserved meat-eating dinosaur footprint in Denali, clearly showing the fleshy pads of skin, claw impressions and skin texture.
Credit: Pat Druckenmiller

In fact, among large dinosaurs, duck-billed dinosaurs (also called hadrosaurs) were probably the most common to live in Alaska during the Cretaceous period, the researchers said. The climate was warmer back then, but still chilly, suggesting that dinosaurs could survive in cooler conditions, team member Gregory Erickson, of Florida State University, told Live Science in 2015.

In 2005, UAF students found Denali's first known dinosaur trackway in the Cantwell Formation near Igloo Creek. Paleontologists have discovered thousands of dinosaur tracks since then, including those of hadrosaurs, also known as duck-billed dinosaurs, but they had yet to find any dinosaur bones, the researchers said.

Other dinosaur trackways that have been found in Denali National Park over the years belong to ceratopsians (a group of herbivorous, beaked dinosaurs that includes triceratops), therizinosaurs (bipedal herbivores) and flying reptiles known as pterosaurs, Erickson said.

However, no dinosaur bones had ever been found in the park, until now. "Now that we have found bones, we have another way to understand the dinosaurs that lived here 70 million years ago," Druckenmiller said.

To learn more about the fossils, Erickson, who studies dinosaur bone and tooth structure, is now cutting some of the fossils into microscopically thin slices so that he can analyze their internal architecture.

Once he examines these thin sections under a high-powered microscope, Erickson will be able to identify what kind of animal left the bones behind. Moreover, the bones' growth lines, which are similar to tree rings, will reveal how fast the animals grew and how old they were when they died.

Original article on Live Science.