The fossil mammal teeth at the centre of my new study with US colleagues<\/a> come from the Late Cretaceous Prince Creek Formation<\/a>, around 73 million years ago. At that time, northern Alaska\u2019s palaeolatitude was roughly 80-85\u00b0N (10-15\u00b0 closer to the north pole than it is today).<\/p>\n Our discovery shows the Arctic was not simply a cold, lifeless edge of the Cretaceous world, but a place where mammals adapted, diversified, migrated and originated. It raises deeper questions about what it means for a species to be native to a place whose landscapes, climates and inhabitants are forever changing.<\/p>\n The Arctic is not an empty landscape now, and nor was it in the deep past. It was a distinctive and demanding biome, with months of winter darkness, freezing temperatures and strong seasonality. <\/p>\n Rivers crossed this landscape. Plants grew through the long light of summer. Dinosaurs<\/a> lived and thrived there, and evidence suggests they reared their young in the Arctic. There was also a diversity of birds<\/a>, fish<\/a> and mammals<\/a>: tenacious denizens of the polar dark.<\/p>\n Colville River in northern Alaska, where tiny multituberculate fossilised teeth were discovered. The teeth we found<\/p>\n Finding miniscule fossil mammals is not the kind of palaeontology that begins with a spectacular skeleton weathering from a cliff. It begins with bulk sediment. Bags and buckets of it. <\/p>\n The material is dug out, washed, sieved through fine screens, dried, then meticulously sorted grain by grain beneath a microscope.<\/p>\n Mammalian palaeontology often depends on fragments: a tooth cusp, a root, a worn edge of enamel. It asks for patience more than drama. The field site may be remote, the landscape vast, but the discovery happens at the scale of a fingertip. It is an act of attention.<\/p>\n The five teeth described in our new study are multituberculates<\/a>: a group of rodent-like mammals that lived alongside dinosaurs. They are the longest-lived mammal group to date, with a history spanning well over 100 million years. Our own species Homo sapiens, by comparison, is only a few hundred thousand years old.<\/p>\n But their success was not permanent. After surviving for longer than any other mammalian lineage, multituberculates eventually vanished, with their last representatives disappearing around the Eocene-Oligocene boundary, roughly 34 million years ago.<\/p>\n Views of five fossilised teeth discovered in Alaska\u2019s Prince Creek Formation. The teeth we found at Prince Creek represent three new species: Camurodon borealis, Kaniqsiqcosmodon polaris and Qayaqgruk peregrinus. The last of these sits especially close to the heart of the story.<\/p>\n Qayaqgruk peregrinus has close evolutionary affinities with a group of multituberculates discovered in Mongolia,<\/a>, indicating that, many millions of years ago, these minute mammals moved between Asia and North America through a polar land corridor.<\/p>\n This was not the world of Pangaea<\/a>, the single giant continent of earlier Earth history. By 73 million years ago, the continents were taking on more familiar shapes, but they had not yet settled into the map we know today.<\/p>\n North America was split by a shallow inland sea, and its far northwestern edge lay near northeastern Asia, creating a high-latitude corridor through which animals could move between continents.<\/p>\n The Arctic corridor itself was not unknown. Fossils of dinosaurs, birds and some mammals have shown that animals were migrating between Asia and North America during the Cretaceous.<\/p>\n But for multituberculates, the picture was much less clear. Their fossil record left open whether they crossed between the continents early and repeatedly, or only later in the Cretaceous. Qayaqgruk peregrinus helps close that gap.<\/p>\n Its name draws on the language of the I\u00f1upiat, Alaska Native people, from the region where the fossils were found. Qayaq is a legendary I\u00f1upiaq hero and wanderer whose journeys are told in The Epic of Qayaq<\/a>.<\/p>\n Many of its Mongolian relatives carry the suffix -baatar, meaning hero in Mongolian, so the name also links its Alaskan discovery to its Asian evolutionary affinities.<\/p>\n Kaniqsiqcosmodon polaris is the oldest known member of the Microcosmodontidae<\/a> family of multituberculates, suggesting this lineage, later known from North America, may have had a polar origin. Camurodon borealis represents the northernmost known occurrence of the North American family Cimolomyidae.<\/p>\n Five teeth are not a complete ecosystem, but they are enough to show these mammals were not occasional strays at the edge of their range. They belonged to the Arctic.<\/p>\n Surviving mass extinction<\/p>\n![\"View](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2026\/06\/file-20260531-63-16n9ma.jpg\")
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\n Pat Druckenmiller<\/a>, CC BY-NC-SA<\/a><\/p>\n![\"Multiple](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2026\/06\/file-20260531-63-jbhm72.png\")
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\n Shelley et al (2026)<\/a>, CC BY-NC-SA<\/a><\/p>\n