73-Million-Year-Old Teeth Reveal Three New Mammal Species That Lived in the Arctic, Among Dinosaurs

Fossilized teeth from the Prince Creek Formation in the Arctic Circle have been traced to three newly identified mammal species that likely walked among dinosaurs about 73 million years ago.

The results, published in the Proceedings of the National Academy of Sciences (PNAS), suggest that these small, rodent-sized mammals – ranging from mice to rats – once lived in what is now northern Alaska and may have settled in the region after traveling from what is now Mongolia.

“Although the polar regions did not harbor the same level of biodiversity as the tropics, they were still very active places where life flourished, extending far back in time,” said first author Sarah Shelley of the University of Lincoln in the United Kingdom, who conducted the study at the University of Colorado at Boulder with the study’s lead author Jaelyn Eberle, in a press release.

These newly identified species could help rewrite our understanding of the role of Arctic regions in evolution and offer new insights into prehistoric biodiversity.

Learn more: The dark fur of prehistoric mammals was the key to survival

The longest living mammals

After analyzing the fossilized teeth, Shelley, Eberle and other members of the research team concluded that the three species were part of the extinct group Multituberculates, one of the oldest groups of mammals to ever walk the Earth.

This group lived for more than 100 million years, according to the press release, spanning from the Jurassic period to the end of the Eocene, about 35 million years ago. They were even among the survivors of the asteroid impact that led to the mass extinction of non-avian dinosaurs.

These newly identified species likely lived during the Late Cretaceous and thrived in the harsh Arctic environment, which at the time still experienced freezing temperatures, potential food shortages, and months of darkness, although it may have been warmer than today. However, these tiny creatures adapted and thrived. This discovery highlights the biodiversity of this region in prehistoric times.

“These three new mammal species add to a growing body of evidence that this ancient Arctic region was home to unique pole-adapted species,” co-author Patrick Druckenmiller of the University of Alaska Fairbanks said in a news release.

What Teeth Can Tell Us About Survival

Multituberculates have long intrigued scientists, who often wonder what has helped these mammals survive so long. These teeth could help unravel this evolutionary mystery.

The team named the species Boreal Camurodonor northern curved tooth; Qayaqgruk peregrinusor the little wandering hero; And Kaniqsiqcosmodon polaris, or tooth decorated with polar gel. They noted that all of the teeth had markedly different shapes, suggesting that they likely relied on different food sources.

While C. boreal“The teeth resembled those of a herbivore, Q. peregrinus And K. polarisThe teeth resembled the teeth of omnivores and they probably ate both insects and some plants.

The flexibility of their diet could have allowed these species to coexist at the same time, according to Shelley, and possibly survive the asteroid impact.

“There’s a lot of diversity in the multituberculate group. They lived incredibly long, and I think they can reveal a lot about the resilience of mammals, not only in the face of mass extinction, but also in the climate stresses that many organisms face today,” Shelley added in the press release.

Adapt through migration

Diet may not have been the only adaptation that led to the survival of this species. According to the study, Q. peregrinus – named after Qayaq, a legendary Alaskan Inuit hero – is closely related to a Mongolian species. The results suggest that Q. peregrinus It may have dispersed from Asia around 92 million years ago and may be one of the first examples of mammals crossing a continent.

“This means that there was a land corridor between Asia and North America for the passage of these small mammals,” Eberle said in the press release. “And this land bridge was already quite active 90 million years ago.”

Evidence from these three species is helping to change our understanding of what life may have been like millions of years ago, from adapting to a changing world and surviving mass extinction to how ancient animals migrated and settled in new areas. These little teeth have quite a story to tell.

“This really challenges our view of native species,” Shelley said in the release. “Deep time reminds us that a place is not just a point on a map, but a long, complex history of landscapes and people.”

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