70 million years ago, the Arctic was not a frozen and isolated region. On the contrary, it harbored an astonishing diversity of mammals and served as a crossroads between continents.
Researchers have identified three new species of rodent-like mammals, about 73 million years old, in the Prince Creek Formation. These animals, named after Inuit culture, lived in extreme conditions with polar nights lasting several months. Their teeth, the only preserved remains, revealed much more than their mere existence.
Late Cretaceous mammals of North America.
Image Wikimedia
The study of the teeth shows that these three species had different diets. One was herbivorous, the other two were omnivorous with distinct preferences. This dietary specialization allowed them to coexist without direct competition, an advantage in an environment where food was scarce. Sarah Shelley, first author of the study, notes that this flexibility may have helped their distant descendants survive the extinction of the dinosaurs.
But the biggest surprise comes from their kinship ties. The species named
Qayaqgruk peregrinus is closely related to a fossil mammal from Mongolia. Researchers estimate that its ancestors migrated from Asia to North America about 92 million years ago. This makes it one of the oldest known examples of mammalian migration between these two continents.
This discovery confirms that a land corridor already connected Asia and North America at that time. Jaelyn Eberle, co-author, specifies that this gateway was active much earlier than previously thought. Mammals have thus crossed continents and reshaped ecosystems for hundreds of millions of years, challenging our view of native species.
The multituberculates, the extinct group to which these three species belong, survived for more than 100 million years. Their success is partly due to their adaptability, as evidenced by these polar fossils.