Three new species of dinosaur-era mammals found in the ancient Arctic

They were found not from whole skeletons, but from fossil teeth from the Prince Creek Formation above the Arctic Circle. From these teeth, scientists were able to understand what animals ate, how they could share resources, and why the ancient Arctic was not a barren wasteland, but a living ecosystem.

Important: we are not talking about modern rodents or an Arctic covered in ice, as it is now. These animals belonged to an extinct group of mammals, the multituberculates. The climate in the Cretaceous period was milder than today's, but the region was still at high latitudes: there were months of darkness, cold and probably a lack of food in winter.

Details

Researchers from the University of Colorado at Boulder and their colleagues studied tiny fossil teeth found in northern Alaska. The finds are about 73 million years old. Back then, the region was above the Arctic Circle, so animals had to live with long winter darkness and pronounced seasonality.

All three new species belonged to multituberculates. This is an extinct group of mammals that existed for more than 100 million years - from the Jurassic period to the end of the Eocene, about 35 million years ago. They even survived the asteroid impact, after which the non-bird dinosaurs disappeared.

The new species have been named Camurodon borealis, Qayaqgruk peregrinus and Kaniqsiqcosmodon polaris. The first name roughly means "northern curved tooth," the second "little travelling hero," and the third "polar frost decorated tooth."

The shape of the teeth suggested to scientists that these animals fed differently. Camurodon borealis was probably a herbivore. Qayaqgruk peregrinus may have been omnivorous and ate insects along with plant food. Kaniqsiqcosmodon polaris also appears to have been omnivorous, but may have relied more on plants.

This is an important detail. In a harsh environment where there is little light in winter and food may be limited, different species may have survived side by side precisely because they did not eat the same things. One species utilised plants more, while another used insects and mixed foods. This sharing of resources may have helped them coexist in the ancient Arctic.

Another finding concerns migrations. One species, Qayaqgruk peregrinus, was found to be close to a species known from what is now Mongolia. This suggests that the ancestors of these mammals may have travelled to North America from East Asia along an ancient land corridor. The authors estimate that such dispersal could have occurred about 92 million years ago.

In other words, the ancient Arctic was not a dead end at the edge of the world. It could have been the route of animal dispersal between Asia and North America.

Why it matters

The discovery changes the conventional view of the polar regions of the past. They are often perceived as poor and marginal compared to the tropics. But the study shows: even at high latitudes, there were complex ecosystems where mammals evolved, adapted and dispersed between continents.

This is also important for understanding the success of multituberculates. They were one of the longest-lived groups of mammals in Earth's history. Perhaps their resilience was due to their ability to quickly occupy different food niches and adapt to complex environments.

The authors do not claim that these ancient animals provide a direct predictor for modern species. But their story helps us understand how mammals survived climatic stresses and changing environments long before humans.

Background

The Prince Creek Formation in northern Alaska has long attracted palaeontologists. Fossils of dinosaurs and other animals that lived at high latitudes during the Late Cretaceous period are found here. Previously, the same research team described a small mammal called Sikuomys mikros, which lived here about 73 million years ago.

Such findings are particularly interesting because the Arctic ecosystems of the past combined a climate that was mild by modern standards with severe seasonality. Even if there were no current ice deserts there, the months of darkness remained a serious challenge for plants and animals.

The new study adds three species to this picture at once and shows that the ancient Arctic was diverse enough to support several closely related species of small mammals with different diets.

Source

Sarah L. Shelley et al, "Arctic ecosystems shaped mammalian dispersal and diversification before the Cretaceous-Paleogene mass extinction," Proceedings of the National Academy of Sciences, 2026.

In the study, scientists described three new species of multituberculate mammals from fossil teeth from the Prince Creek Formation in northern Alaska. The finds are about 73 million years old. Based on the shape of the teeth, the authors drew conclusions about the different diet of these animals, and the kinship of one of the species pointed to the ancient dispersal of mammals between East Asia and North America.