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Ice Age Ankle Biters

1 April 2012 1:12 pm
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Adapted from Wikipedia and AMNH/Creative Commons

Fearsome fangs. Artist's reconstruction of Lemmus scimitardontti, the saber-toothed lemming, which-along with mammoths, mastodons, and other megafauna-died out at the end of the last ice age.

A serendipitous hike along a remote Norwegian fjord has yielded innumerable fossils of one of the most unusual creatures to have died out at the end of the last ice age: the saber-toothed lemming.

Paleontologists have dubbed the species Lemmus scimitardontii, naming the tiny, enigmatic mammal for its most prominent feature: the sharp, stout fangs that measure about twice the length of its skull. The creatures' remains—a bone-studded, furry mat that if fully excavated would probably cover an area equal to three soccer fields—are entombed in a 20-centimeter-thick layer of fine-grained sediment about 30 meters high on the south face of the fjord, says D. Avril Poisson, a vertebrate paleontologist at the High-Arctic Institute of the Museum of Montreal (HI-MOM). When the ice sheet that smothered northern Europe melted at the end of the last ice age, removing an immense weight from Earth's crust, the glacial sediments that had accumulated on the floor of the fjord—and the bizarre fossils contained within—rose to their current level.

Radiocarbon dating suggests that all of the lemmings died in a single event, probably stampeding over a cliff along the fjord in a torrent of fur and fang, just as their modern kin are wont to do. The large concentration of Arctic mango pollen trapped in the creatures' fur indicates that the lemmings took their ill-fated plunge on an exceptionally warm spring afternoon—most likely on a Tuesday, Poisson speculates.

"I'm amazed at how much information we've gleaned from these fossils," she notes. "Our reconstruction of the fascinating lifestyle of these mysterious creatures is just beginning."

L. scimitardontii was about the size of a guinea pig, substantially larger than today's lemmings but a far cry from majestic Ice Age megafauna such as mammoths, mastodons, and giant ground sloths. In all respects other than its unusual size and its saberlike teeth, the previously unknown species is just like its modern-day kin—and, indeed, like many other mostly herbivorous rodents.

"Fangs like this aren't unknown in the animal kingdom, but they certainly appear out of place on such a tiny vegetarian," says I.D. Goode, longtime scientific consultant to the Kansas State Board of Education. "How could such teeth have evolved? What purpose could they have served? This doesn't seem like a very smart design," he notes.

One purpose the fangs could serve, Poisson counters, is to help members of the species recognize one another. Also, she notes, male saber-toothed lemmings could have used their teeth in combat when competing for food, territory, or mates.

Or, more intriguingly, the fangs may have been an oddity of evolution that didn't provide any benefits to individual lemmings yet still may have been useful to the species, says Poisson. Any predators that gobbled one of these lemmings would have likely suffered massive internal bleeding as the saber-toothed carcass made its way through the digestive system, she notes. And if death from such hemorrhaging didn't occur within hours, the pain and near-certainty of long-term infection would likely serve as not-so-subtle warnings to other predators, she adds.

"Lest we forget, in past eras as well as today, evolution has produced a myriad of wonderful creatures," says Poisson.

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