Its a fitting title. While the little ice mouse wasnt really a mouse, rather belonging to a now-extinct household of mammals called Gypsonictopidae, it was certainly small. The furry critter may have looked a bit like a modern-day shrew and weighed an estimated 11 grams or less than an empty aluminum soda can. It likewise lived year-round in northern Alaska, which at the time lay much further north, above the planets Arctic Circle. There, the ice mouse likely weathered as much as four months of endless darkness in the winter season and temperatures that fell listed below freezing.
” These guys most likely didnt hibernate,” stated Eberle, curator of fossil vertebrates at the CU Museum of Natural History and teacher in the Department of Geological Sciences. “They remained active all year long, burrowing under leaf litter or underground and feeding on whatever they might sink their teeth into, probably bugs and worms.”.
A group of paleontologists digs along the banks of the Colville River in northern Alaska. Credit: Kevin May.
She and her colleagues had to be equally tenacious to find the fossil animals: The scientists identified the brand-new types from only a handful of tiny teeth, each about the size of a grain of sand.
” I always like working at the ends of the Earth,” Eberle stated. “You never understand what youre going to find, but you know its going to be brand-new.”.
Those minute fossils are offering researchers a new window into ancient Alaska, stated study co-author Patrick Druckenmiller, director of the University of Alaska Museum of the North.
” Seventy-three million years earlier, northern Alaska was home to an ecosystem unlike any on Earth today,” he said. “It was a polar forest teeming with dinosaurs, little mammals, and birds. These animals were adjusted to exist in an extremely seasonal environment that included freezing winter season conditions, likely snow, and as much as four months of total winter darkness.”.
Venturing north.
Getting to completions of the Earth isnt constantly easy.
The scientists, including paleontologists from the University of Alaska Fairbanks and Florida State University, unearthed the fossils from sediments along the banks of the Colville River– not far from the Beaufort Sea on Alaskas northern coast. The site, part of whats called the Prince Creek Formation, is so remote the group travels the 75 or so miles from Deadhorse, Alaska, by snowmobile or bush airplane.
” Our teams research study is revealing a Lost world of Arctic-adapted animals,” said Gregory Erickson, a co-author of the research study at Florida State University. “Prince Creek works as a natural test of these animals physiology and habits in the face of drastic seasonal climatic changes.”.
The late William Clemens of the University of California, Berkeley was also a co-author of the brand-new research study.
JP Cavigelli of the Tate Geological Museum in Wyoming holds up a tiny mammal tooth. Credit: Jaelyn Eberle.
Unlike dinosaurs from the same period, which left large bones, the only fossils remaining from the regions mammals are a couple of teeth and pieces of jaws. To recuperate these valuable specimens, the group collects pails of dirt from the riverbanks. In the laboratory, the scientists get rid of the mud and sort what stays under a microscope.
” You look under the microscopic lense and see this best little tooth,” Eberle stated. “Its so tiny.”.
Safety underground.
When it comes to the ice mouse, those best little teeth have actually influenced a best little secret.
For numerous groups of mammals in the world, species tend to get bigger at greater latitudes and cooler environments. The ice mouse and its close cousins seem to follow the opposite pattern. Paleontologists have discovered associated types living thousands of miles to the south that were 3 to five times larger than Sikuomys mikros.
Since there was so little to eat during the winter in Alaska, Eberle thinks the ice mouse was so small.
” We see something comparable in shrews today,” she said. “The concept is that if youre really little, you have lower food and energy needs.”.
Sikuomys mikros may have invested the cold months in Alaska underground. In the end, such a below ground lifestyle may have been a blessing for animals like the ice mouse. Burrowing mammals might have stood a much better opportunity of surviving the extreme conditions that followed the meteorite crash that eliminated the dinosaurs 66 million years ago.
Reference: “A brand-new tiny eutherian from the Late Cretaceous of Alaska” by Jaelyn J. Eberle, William A. Clemens, Gregory M. Erickson and Patrick S. Druckenmiller, 5 August 2023, Journal of Systematic Palaeontology.DOI: 10.1080/ 14772019.2023.2232359.
While the little ice mouse wasnt in fact a mouse, rather belonging to a now-extinct family of mammals called Gypsonictopidae, it was certainly tiny. It likewise lived year-round in northern Alaska, which at the time lay much further north, above the worlds Arctic Circle.” Seventy-three million years ago, northern Alaska was home to an ecosystem unlike any on Earth today,” he stated. Unlike dinosaurs from the very same time duration, which left behind big bones, the only fossils staying from the regions mammals are a couple of teeth and fragments of jaws. Sikuomys mikros may have invested the cold months in Alaska underground.
A fossilized Sikuomys mikros tooth about the size of a grain of sand seen under the microscopic lense. Credit: Jaelyn Eberle
Paleontologists operating in northern Alaska have actually discovered a tiny fossil mammal that flourished in what might have been amongst the coldest conditions in the world about 73 million years ago.
The scientists, led by Jaelyn Eberle of the University of Colorado Boulder, described the Late Cretaceous animal in a research study just recently published in the Journal of Systematic Palaeontology.
They offered it the clinical name Sikuomys mikros– from “Siku,” an Iñupiaq word for “ice,” and “mys” and “mikros,” the Greek words for “mouse” and “little.”.