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Researchers identify primitive fossil bear with a sweet tooth

Digital reconstruction of the Canadian Arctic fossil bear Protarctos abstrusus. (Image: Xiaoming Wang, Natural History Museum of Los Angeles County)
Dental Tribune International

Dental Tribune International

Fri. 5. January 2018

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LOS ANGELES, U.S.: Researchers have identified remains of a 3.5-million-year-old bear from a fossil-rich site in Canada’s High Arctic. Their study showed not only that the animal is a close relative of the ancestor of modern bears—tracing its ancestry to equivalent-aged extinct bears from East Asia—but also that it had a sweet tooth, as evident from cavities in the teeth.

The scientists identified the bear as Protarctos abstrusus, which was previously only known from a tooth found in Idaho. Showing its transitional nature, the animal was slightly smaller than a modern black bear, with a flatter head and a combination of primitive and advanced dental features.

“This is evidence of the most northerly record for primitive bears, and provides an idea of what the ancestor of modern bears may have looked like,” said Dr. Xiaoming Wang, lead author of the study and Curator of Vertebrate Paleontology at the Natural History Museum of Los Angeles County. “Just as interesting is the presence of dental caries, showing that oral infections have a long evolutionary history in the animals, which can tell us about their sugary diet, presumably from berries. This is the first and earliest documented occurrence of high-calorie diet in basal bears, likely related to fat storage in preparation for the harsh Arctic winters.”

The research team, which included co-author Dr. Natalia Rybczynski, a research associate and paleontologist with the Canadian Museum of Nature, were able to study recovered bones from the skull, the jaws and teeth, as well as parts of the skeleton, of two individuals.

The bones were discovered over a 20-year period by Canadian Museum of Nature scientists, including Rybczynski, at a fossil locality on Ellesmere Island known as the Beaver Pond site. The peat deposits include fossilized plants indicative of a boreal-type wetland forest and have yielded other fossils, including fish, beaver, small carnivores, deerlets and a three-toed horse.

The findings show that the Ellesmere Protarctos lived in a northern boreal-type forest habitat, where there would have been 24-hour darkness in winter, as well as about six months of ice and snow.

The teeth of both Protarctos individuals show signs of well-developed dental cavities, which were identified using CT scans by Dr. Stuart White, professor emeritus with the University of California, Los Angeles School of Dentistry. The cavities underline that these ancient bears consumed large amounts of sugary foods, such as berries. Indeed, berry plants were found preserved in the same Ellesmere deposits as the bear remains.

“We know that modern bears consume sugary fruits in the fall to promote fat accumulation that allows for winter survival via hibernation. The dental cavities in Protarctos suggest that consumption of sugar-rich foods like berries, in preparation for winter hibernation, developed early in the evolution of bears as a survival strategy,” explained Rybczynski.

The study, titled “A basal ursine bear (Protarctos abstrusus) from the Pliocene High Arctic reveals Eurasian affinities and a diet rich in fermentable sugars,” was published online in the Scientific Reports journal on 18 December 2017.

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