Opening details

Evidence of ancient life was hidden at the foot of the mountain range. The fossils found in the Nanushuk Formation beneath the De Long Mountains provide a window into the thriving Cretaceous ecosystem where dinosaurs of all sizes lived, the researchers said in a statement.

Paleontologists have been exploring this place since 2015. Although they were unable to identify specific species, they found 75 tracks left by carnivorous and herbivorous dinosaurs.

Theropod track / Photo: Anthony Fiorillo

This place was incredibly rich in dinosaur tracks. It was like we were walking in a forest millions of years ago.
– says the study’s lead author, Anthony Fiorillo, executive director of the New Mexico Museum of Natural History and Science.

Fiorillo and his colleagues found that the site preserved an ancient landscape of fossilized logs, leaves, tracks and feces 60 centimeters wide.

• Most of the tracks were left by bipedal herbivorous dinosaurs, collectively known as bipedal ornithosaurs. This group includes animals such as skull-headed pachycephalosaurs that were not identified in the study.
• Four-legged herbivores or four-legged ornithosaurs made few tracks.
• Some of these belonged to ceratops, a group that includes the three-horned triceratops.
• Carnivorous dinosaurs also lived in the ecosystem. Theropods that were not birds of prey left the least traces. Some of these tracks are in the size range of Turonian theropods, such as the 1-meter-long tyrannosaur Suskityrannus, nicknamed “mini-rex,” and the horse-sized Timurlengia, the authors noted.
• Shorebirds left 15% of identified tracks. Nearly half of North America’s shorebirds breed in the Arctic during the warmer months, and the authors note that the high frequency of extinct shorebird tracks there suggests the same thing occurred in the Cretaceous.

Petrified tree trunk / Photo: Paul McCarthy

The team also used this formation to learn more about the hot and humid climate of the ancient Arctic. By calculating the average annual rainfall from pieces of wood, they found: polar dinosaurs lived in a climate similar to modern-day South Florida, meaning it was quite warm. “The temperature was much warmer than today, and perhaps most interestingly, there was a lot of rain. The samples we analyzed show that this was roughly equivalent to modern-day Miami. That’s pretty significant.”– says Fiorillo.