A raccoon-sized bear that lived a short and painful life some 32 million years ago has suddenly risen to prominence thanks to a new paper that has declared it a new species, Eoarctos vorax. The so-called “dawn bear the voracious eater” helps to establish North America as an important venue for the evolution of early bears, a process scientists have largely relegated to Europe.
Paleontologists first unearthed the skeleton in 1982 from the Fitterer Ranch site in southwestern North Dakota, but proper classification of it has waited until the release of the new paper. It describes a nearly complete skeleton in “exquisite” condition, save for some interesting damage to the jaw.
The new paper that classifies the skeleton was a collaboration between the Natural History Museum of Los Angeles County and the North Dakota Geological Survey.
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A Small Bear in a Big Family
The paper identifies the little bear as an arctoid, a sprawling group of mostly carnivores that includes a range of animals, from huge elephant seals to slender weasels. In between there are pandas, raccoons, black bears and some 268 extinct and surviving genera, what the paper calls “unparalleled diversity.” The dawn bear played a major role in this zoological flowering, though it’s not considered to be an ancestor to modern bears.
The dawn bear was remarkably small and weighed only about 9.5 pounds at most, similar to a house cat. It survived on its ability to dart from ground to tree, where it climbed with ample claws to escape danger. On the ground, its flat feet allowed it to range widely to forage, covering tens of kilometers in a single day. Along the way, the bear found in 1982 discovered some type of hard food (probably mollusks, the paper says) that it had to crush with its teeth.
What Killed the Dawn Bear?
The bear had an unusual adaptation – molars capable of crushing hard objects – which was strange for a small carnivore. However, they were not strong enough to withstand the force, and the chewing broke the crowns of its lower right molars. When that injury became infected, the disease spread to the roots and bones, the paper surmises.
Infection is probably what killed the bear, it says, given the lack of bite marks on the skeleton or other damage. The researchers estimated from the skull left behind that the bear had a relatively small brain but a massive olfactory bulb sticking out the front of it, which would have processed smells. The relative size of the bulb is perhaps greater than in any other carnivore, the paper says, but this may just be due to the smallness of the bear’s cerebrum (its central brain).
The dawn bear died as a young adult during the Oligocene epoch, as the Antarctic glacier was growing and the globe was cooling. Many other arctoids, like the bear, were venturing down from the trees and exploring terrestrial spaces. Other animal groups such as the canids were undergoing changes, as well, and diversifying at this time.
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