A 12-foot (3.65-meter) Columbian mammoth tusk has been unearthed in Idaho and scientists say more of the fossil skeleton might still be buried at the site.

Researchers say the large herbivore lived 72,000 to 200,000 years ago and was about 16 to 19 when it died. Its left tusk was found earlier this year at American Falls Reservoir.

"That's a really good find out there," said Mary Thompson, collections manager at the Idaho Museum of Natural History at Idaho State University. "We know we have Columbian mammoth (in the region). We're constantly finding bits and pieces."

Researchers with the university unearthed about 60 percent of the skull last year and about 8 feet (2.4 meters) of the right tusk after a volunteer with the U.S. Bureau of Reclamation spotted the fossil.

Rising water at the reservoir forced a stop to the excavation, but researchers returned this year when the water dropped and removed the tusk last week.

Thompson said the tusk will likely go on display next year.

She said the recently found mammoth specimen is likely better preserved than others in the area because it spent thousands of years under the sediment of the ancient American Falls Lake that formed when a lava flow dammed what is now the Snake River.

That lava dam eventually eroded and the lake disappeared, scientists say, about 14,500 years ago. More recently, the fossil skeleton was covered by the man-made American Falls Reservoir.

Low water and erosion uncovered the fossil late last year, Thompson said.

Thompson said the region is one of the best North American sites for finding a rich diversity of prehistoric mammal fossils, though intact mammoths are rare and the unearthed tusk is the first complete tusk found in the area.

"It's been very well preserved in the soil and sediments," said Jenny Huang, an archaeologist with the U.S. Bureau of Reclamation for the Snake River Region. "We have an opportunity to learn quite a bit about this particular animal because of the state of preservation."

The tusk is currently encased in plaster and being stored at a Bureau of Reclamation office. Huang said it will be delivered to the university with a week.

She said researchers couldn't find more than the tusk in the most recent dig, but more fossil bones might be scattered about.

Southeastern Idaho, Thompson said, at one time served as a corridor that brought in now-extinct mammals from Asia as well as South America. Some other fossil discoveries in the region include camels that were larger than modern-day camels, North American lions that stood 5 feet at the shoulder, giant sloths, dire wolves and mastodons.

She said the most recent discovery is a prehistoric giant bison, and is possibly a rare female find. One of its horns is about 4 feet long. If it is a female, Thompson said, that could provide scientists some clues about the differences in average size between males and females of that extinct species.

However, American Falls Reservoir is filling up again so researchers have had to leave the area without being able to unearth the giant bison fossil.

"We're going to have to wait until the water goes down," Thompson said.

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