The bear that left a 3-foot-long claw mark in an Ice Age clay bank was the largest bear species ever to walk the Earth, about 6 feet tall...

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SPRINGFIELD, Mo. — The bear that left a 3-foot-long claw mark in an Ice Age clay bank was the largest bear species ever to walk the Earth, about 6 feet tall at the shoulder and capable of moving its 1,800-pound body at up to 45 mph in a snarling dash for prey.

The claw mark by the extinct giant short-faced bear still looks fresh today in a southwestern Missouri cave that some scientists are calling a national treasure — an Ice Age time capsule sealed for thousands of years.

Discovered accidentally five years ago on the outskirts of Springfield, Riverbluff Cave is slowly yielding its fossil treasures as a small team of scientists and volunteers gingerly explores it while trying to preserve a rich bed of remains.

Remains in the cave date back at least 830,000 years and possibly more than 1 million years. At some point at least 55,000 years ago, it was sealed by rocks and mud until a construction crew blasted a hole in one end while building a road in 2001.

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The first major excavation is set for this fall after years of carefully surveying the 2,000-foot-long cave and collecting remains from the cave floor or protruding from the limestone and clay walls.

The finds so far include mammoth and horse bones and beds clawed out of the clay by the short-faced bear, possibly while denning with cubs. Peccary tracks are the first proof that herds of the piglike animals roamed in caves rather than just being dragged in by predators.

There are tracks of large cats, possibly saber-toothed tigers or American lions. Footlong shells of previously unknown turtle species stick out of a wall.

Lead paleontologist Matt Forir said every discovery raises new questions. Mammoth bones and a juvenile tooth dated around 630,000 years ago came from one of two species and it will require more adult remains to tell which one it is. He hopes the excavation will provide answers.

“We either have the oldest wooly mammoth in North America or the youngest Meridian mammoth. Most of the stuff in this cave is like that, always raising more questions,” he said.

Greg McDonald, senior curator of natural history for the National Park Service, said Riverbluff Cave offers rare insight into Ice Age ecology. By combining animal bones with other traces, including tracks and dung, it can show how Ice Age animals lived, what they ate and what killed them off.

“It’s a unique combination of traces and the quality of preservation that makes it such a phenomenal site,” McDonald said. “It’s probably going to become a major reference site that will help us better understand the remains we have at other sites.”

If research confirms that fossilized dung in the bear beds is from the short-faced bear, it would be a first and could provide real clues about what the bears ate, McDonald said.

The cave remains closed to the public to preserve its remains.

But with the help of the Springfield-Greene County library system and Ozarks Technical Community College, Forir installed a fiber-optic network that lets him broadcast pictures from the cave for school classes and the public.

“This is where the Ice Age meets the Space Age,” he said.

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