Fossilized teeth discovered in Alaska’s far north have revealed three previously unknown mammal species that lived 73 million years ago during the Late Cretaceous. Researchers say the discoveries support the idea that harsh polar conditions may have encouraged species to adapt and diversify rather than simply survive.
When people picture ecosystems from this period, dense forests and warmer regions usually come to mind first. Polar environments, by comparison, were often treated as marginal ecosystems with limited evolutionary significance.
New research based on fossils from the Prince Creek Formation challenges that view. Scientists identified three extinct mammals and found that differences in their teeth suggest they were filling different roles in the same environment. According to the study published in the Proceedings of the National Academy of Sciences, the ancient Arctic may have played a bigger part in mammal evolution than previously thought.
Tiny Mammals with Surprisingly Different Lifestyles
The three species belonged to a group called multituberculates, extinct mammals named after the rows of small bumps, or tubercles, on their teeth. Researchers named the species Camurodon borealis (“Northern curved-tooth”), Qayaqgruk peregrinus (“the little wandering hero”), and Kaniqsiqcosmodon polaris (“polar frost ornamented tooth”).
Their teeth gave away something unexpected. These animals were not all eating the same thing. The research, published in PNASfound that Camurodon borealis appears to have been a herbivore. And Qayaqgruk peregrinus likely had a more flexible diet that included insects and plants. Meanwhile, Kaniqsiqcosmodon polaris seems to have been an omnivore with a stronger focus on vegetation.
That variety matters because it suggests these mammals were splitting resources and occupying different ecological niches instead of competing directly with one another.
Life in the Frozen Arctic
The Arctic inhabited by these mammals looked very different from the modern region but remained demanding. Researchers describe an environment with heavy snowfall, average annual temperatures around 6°C (42°F), and winter darkness lasting up to four months. Even so, these small mammals were not disappearing, they were diversifying.
Sarah Shelley of the University of Lincoln said polar regions have been active places for life to develop for much longer than people often assume.
“There’s a lot of diversity in the multituberculate group. They lived for an incredibly long time, and I think they can reveal a lot about the resilience of mammals, not just to the mass extinction, but also to climatic stresses that many organisms are facing today,” she explained in a statement available on The University of Lincoln’s website.
One Species Crossed Continents First
One of the newly described mammals stood out for another reason. As explained by the study team, the species appears closely related to multituberculates previously identified in present-day Mongolia.
They think its ancestors may have reached North America across a land bridge around 92 million years ago. That would make it one of the earliest known examples of mammals moving between continents.
Its name contains a quiet reference to that history. Many Mongolian multituberculate species include the word bataar, meaning “hero,” which inspired the species’ nickname, “the little wandering hero.”
Multituberculates themselves had an unusually long history. They survived for more than 100 million years, beginning in the Jurassic and lasting until the end of the Eocene around 35 million years ago. Patrick Druckenmiller, a paleontologist at the University of Alaska Fairbanks, said that:
“These three new mammal species add to a growing body of evidence that this ancient Arctic region was home to unique, polar-adapted species.”
Findings from the site already include predators, large plant-eaters, and an expanding record of small mammals, helping reveal an Arctic ecosystem that was far more active and diverse than once imagined.
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