Rhino- and hippo-like beasts and other large mammals roamed the Arctic 53 million years ago in a climate that reached 70 degrees Fahrenheit, and they basked part of the year in a warm midnight sun and stayed put when the sun dropped below the horizon for months at a time, new research indicates.
Based on analyses of carbon and oxygen isotopes in the fossil teeth of three species, researchers at the University of Colorado at Boulder concluded that during the dark months, the creatures shifted their diet radically.
Their summer fare of flowering plants, leaves and aquatic vegetation gave way to twigs, leaf litter, evergreen needles and fungi during the mild winters, which probably got no colder than just above freezing.
The fossils were found on Ellesmere Island, near Greenland, which since 1975 has yielded a remarkable remains of ancient creatures such as alligators, aquatic turtles, giant tortoises, snakes and flying lemurs, one of the earliest primates. Today, the region is high arctic of tundra, permafrost, ice sheets, sparse vegetation and small mammals.
In the June issue of Geology, the researchers conclude that the ancient mammals migrated south via land bridges over millions of years as the climate cooled, a pattern that could reverse with Earth’s current warming. “We are hypothesizing that lower-latitude mammals will migrate north as the temperatures warm in the coming centuries and millennia,” said Jaelyn Eberle, an assistant professor at UC.
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