Paleontologists working in northern Alaska small fossil mammal that it developed in some of the coldest conditions on Earth, about 73 million years ago. Its appearance resembled a modern shrew.
Researchers led by Jaelyn Eberle of the University of Colorado Boulder (USA) described this Late Cretaceous animal in a study published this month. Journal of Systematic Paleontology.
Creature baptized with scientific name sikuomys microsfrom ‘Siku’, an Iñupiaq word for ‘ice’, and ‘mys’ and ‘mikros’, the Greek words for ‘mouse’ and ‘small’.
It is a name that does justice to the characteristics of the animal. Although the little ice rat he wasn’t really a mouseIt belonged to a now-extinct family of mammals called mammals. GypsonictopidaeIt was definitely too small. Its appearance should be similar to that of a modern shrew, and weighs about 11 gramsi.e. less than an empty aluminum soda can.
He also lived year-round in northern Alaska, which was then much further north, above the planet’s polar circle. There, the ice rat probably endured up to four months of eternal darkness in winter and temperatures falling below freezing.
“These animals probably didn’t hibernate,” says Eberle, a keeper of fossil vertebrates and a professor in the Department of Geological Sciences at the University of Colorado Boulder Museum of Natural History. “They were active throughout the year.by burrowing under leaf litter or underground and feeding on anything they can get their teeth into, possibly insects and worms.”
He and his colleagues had to be equally ambitious to uncover these fossil remains: The researchers identified the new species from just a handful of fossils. tiny teeth, each the size of a grain of sand.
“I’ve always loved working on the other side of the world,” Eberle said. “You never know what you will find, but you know it will be new.”
These tiny fossils offer researchers a new window into ancient Alaska, said Patrick Druckenmiller, director of the University of Alaska Northern Museum and co-author of the study.
“Seventy-three million years ago, northern Alaska was home to an ecosystem unlike any found on Earth today,” he said. “One arctic forest full of dinosaurs, small mammals and birds. These animals have adapted to exist in a highly seasonal climate that includes icy winter conditions, snow and up to four months of complete winter darkness.”
go north
Reaching the end of the world is not always easy. Researchers have excavated fossils from sediments on the banks of the Colville River, not far from the Beaufort Sea on Alaska’s north coast. Part of what is now called the Prince Creek Formation, the area is so remote that the team has to cover the distance of about 75 miles from Deadhorse, Alaska, on a snowmobile or small plane.
“Our team’s research reveals the ‘lost world’ of animals that have adapted to the Arctic,” said study co-author Gregory Erickson, of Florida State University. “Prince Creek serves as a natural test for the physiology and behavior of these animals in the face of severe seasonal climate fluctuations.”
Unlike dinosaurs of the same era, which left large bones behind, The only remaining fossils of mammals in the region are some teeth and jaw fragments.. The group collected buckets of soil from the banks of the river to recover these precious specimens. In the laboratory, the researchers washed the sludge and classified the filtered material with the help of a microscope.
If he lived this far north, why was he so small?
When it comes to the ice rat, these perfect little teeth have revealed a little mystery.
In many mammalian groups on earth, species tend to grow in higher latitudes and colder climates. But the ice rat and its close cousins seem to follow the opposite pattern. Paleontologists have found related species that live thousands of kilometers south and are three to five times larger than us. sikuomys micros.
Eberle suspects an ice rat it was very small because there was very little to eat winter in Alaska.
“We’re seeing something similar in mice today,” he said. “The idea is that if you’re very small, you need less food and energy.”
HE sikuomys micros could spend the cold months underground in Alaska. In the end, such an underground lifestyle may have been a boon for animals like the ice rat. Burrowing mammals may have had a better chance of surviving in the harsh conditions that followed the meteorite impact that killed the dinosaurs 66 million years ago.
Reference work: https://www.tandfonline.com/doi/abs/10.1080/14772019.2023.2232359?journalCode=tjsp20
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