Footprints of duck-billed dinosaurs, armored dinosaurs and a tyrannosaur discovered in Aniakchak National Monument, southwestern Alaska, shed new light on the Cretaceous period, according to new research.

Dinosaur fossils are well-known from Alaska, mostly from Denali National Park and the North Slope, but there are very few records of dinosaurs from the Alaskan Peninsula in the southwest part of the state.

In this new study, a team of paleontologists led by Dr. Anthony Fiorillo from the Perot Museum of Nature and Science found and analyzed dinosaur trackways in Aniakchak National Monument, located approximately 416 miles (670 km) southwest of the city of Anchorage, Alaska.

The trackways were preserved in Chignik Formation, a series of coastal sediment deposits dating back to the Late Cretaceous epoch, around 66 million years ago.

Dr. Fiorillo and colleagues identified over 75 new track sites including dozens of dinosaur footprints.

“Most of the combined record of tracks can be attributed to hadrosaurs, the plant-eating duck-billed dinosaurs. Tracks range in size from those made by full-grown adults to juveniles,” they said.

“Other tracks can be attributed to armored dinosaurs, meat-eating dinosaurs, and two kinds of fossil birds.”

“The track size of the predatory dinosaur suggests a body approximately 20-23 feet (6-7 m) long, about the estimated size of the North Slope tyrannosaurid Nanuqsaurus.”

Previous research on dinosaur remains from northern Alaska found that hadrosaurs were most abundant in coastal habitats. The trackways documented in this study reveal that the same trend was true in southern Alaska.

“Understanding habitat preferences in these animals will contribute to understanding of how ecosystems changed through time as environmental conditions shifted and dinosaurs migrated across northern corridors between continents,” the researchers said.

“Our study shows us something about habitat preferences for some dinosaurs and also that duck-billed dinosaurs were incredibly abundant,” Dr. Fiorillo said.

“Hadrosaurs were as commonplace as cows, though given we are working in Alaska, perhaps it is better to consider them the caribou of the Cretaceous.”

The study was published online in the journal PLoS ONE.

_____

A.R. Fiorillo et al. 2019. Dinosaur ichnology and sedimentology of the Chignik Formation (Upper Cretaceous), Aniakchak National Monument, southwestern Alaska; Further insights on habitat preferences of high-latitude hadrosaurs. PLoS ONE 14 (10): e0223471; doi: 10.1371/journal.pone.0223471