The truth of the tooth

GRAIN VALLEY, Mo. -- Everything about the bones that turned up in a Grain Valley back yard last summer suggested to scientists that they came from a 50,000-year-old mastodon.

But evidence yielded by additional digging has led the experts to conclude they were off-base. The remains are actually those of a mammoth that lived 500,000 to 1 million years ago, according to the scientists.

"The tooth was absolutely definitive," said Craig Sundell, a University of Kansas paleontologist who is leading the dig.

The 9-inch, 5-pound fossilized molar emerged in August, several weeks after a contractor came upon the bones while excavating a lake behind the home of Steve and Debbie Gildehaus in eastern Jackson County.

Debbie Gildehaus contacted the University of Kansas about the discovery, and the paleontologists went to work immediately.

They quickly unearthed what appeared to be a rib and another long bone from a baby mastodon, an elephant-like mammal that lived in North America about 10,000 to 50,000 years ago. Mastodon skeletons are not uncommon on the continent.

But the large tooth identified the remains as those of a mammoth -- a larger type of prehistoric elephant that crossed from Asia into North America about 1.7 million years ago. The thickness of the enamel and the number of ridges on the molar provide a rough estimate of the animal's age, perhaps 40 to 50 years old at death.

Discovery of the tooth helped explain a puzzle that emerged as the scientists dug at the site. The bones were buried under 50 to 60 feet of clay, which could have been washed to Grain Valley when a nearby ice dam melted. But glaciers were much farther north 50,000 years ago, when a mastodon would have lived.

Wakefield Dort, a retired University of Kansas geology professor, said glacial ice had advanced as far south as what is now Lee's Summit at the time the mammoth roamed modern-day Missouri.

As the ice receded north, it left a series of lakes and a shallow watering hole in what is now the Gildehauses' back yard. The mammoth probably had gone there for a drink and died on the banks, Dort said.

As the ice continued to recede, it released clay, and the mammoth was buried underneath it, Dort said.

Remains of other animals found at the site include a giant sloth, an armadillo and a deer.