More than 70 million years ago, the Arctic was not the frozen, empty place we know today. Instead, it was home to forests, dinosaurs, and small furry mammals that managed to survive long winters with months of darkness.
Now, researchers from University of Colorado Boulder and their collaborators have discovered three previously unknown species of ancient mammals that once lived in what is now northern Alaska.
The findings, published in the Proceedings of the National Academy of Sciences, reveal that the ancient Arctic was far more important for evolution than scientists once believed.
The newly identified species were named Camurodon borealis, Qayaqgruk peregrinus, and Kaniqsiqcosmodon polaris. Although their names are complicated, the animals themselves were small, roughly the size of mice or rats.
These creatures belonged to an extinct group of mammals called multituberculates. They lived during the age of dinosaurs and were among the most successful mammals in Earth’s history.
Multituberculates survived for more than 100 million years, far longer than humans have existed. Remarkably, they even survived the asteroid impact that wiped out the non-avian dinosaurs about 66 million years ago.
The fossils were discovered in Alaska’s Prince Creek Formation, a famous Arctic fossil site dating back around 73 million years.
Even during the dinosaur age, the Arctic experienced long periods of winter darkness, freezing temperatures, and seasonal food shortages. Scientists say surviving in such extreme conditions would have been difficult for small mammals.
Yet these species not only survived, they appeared to thrive.
Researcher Sarah Shelley explained that the discoveries add to growing evidence that the ancient Arctic was home to unique animals specially adapted to polar conditions.
The researchers identified the species mainly from fossil teeth. Those teeth revealed important clues about how the animals lived and what they ate.
One species appeared to mainly eat plants, while the others likely ate a mixture of plants and insects. Scientists believe these different diets may have helped multiple species survive together in an environment where food resources were limited.
According to the researchers, this flexibility may also help explain why multituberculates were so successful for such a long time and managed to survive major environmental disasters.
The discovery also revealed something surprising about ancient migration.
One of the species, Qayaqgruk peregrinus, appears to be closely related to mammals previously found in what is now Mongolia. This suggests the ancestors of these Arctic mammals traveled from Asia to North America roughly 90 million years ago.
Scientists believe this migration was possible because a land bridge once connected the two continents.
Researcher Jaelyn Eberle said the findings show that this land route between Asia and North America was already active much earlier than many scientists previously realized.
The study also challenges modern ideas about what counts as a “native” species. Over millions of years, animals have constantly moved between continents, reshaping ecosystems again and again.
The researchers say these tiny Arctic mammals offer a valuable reminder that life on Earth has always been adaptable, resilient, and constantly changing.
