A St. Paul family's hike through the woods near Fort Snelling unveiled an anthropological mystery Sunday afternoon when they spotted the unmistakable shape of a human skull resting in the mud near a creek.

Missing its teeth and lower jaw, the "worn and weathered" skull was plainly visible, said Daniel Greenfield, who was out walking his dog with his wife, Andrea, and children Emma, 12, and Henry, 9.

"You almost looked around like, 'Was this a prank?' or something like that," Greenfield said Monday. "It was just there and it was face up, and it was very obvious."

They contacted police, and the skull was taken to the Hennepin County medical examiner's office. It could take at least a week to determine the person's sex, approximate age and possible ancestry.

"In a perfect world you'd actually figure out this person's name," said Andrew Baker, chief medical examiner for Hennepin County. At this point, he said, "the only thing I know with certainty is that it's a human skull."

A spokesman for the Minneapolis Park Police said the site where the skull was found is not considered a crime scene. It's not uncommon to find bones in the area, said Lt. Mark Swanson of the Minneapolis Park Police. Still, finding a skull is unusual, he added.

The area where the Greenfields said they found the skull has a rich history of human settlement, both by American Indians and Europeans.

Historic Camp Coldwater, founded in 1820, is just west of the dog park that the Greenfields were using at the time. It's long been suggested that there are American Indian burial sites in the area. Activists against the Hwy. 55 reroute argued that that project would disturb Dakota graves, though no graves were found.

Greenfield said his family had wandered to an area near a bluff where small creeks of meltwater were running. The skull was earth-colored, he said, missing its teeth and lower jaw. It had a crack along its side. Greenfield said he didn't see footprints in the mud that could have suggested the skull was placed there recently. He speculated that it could have fallen from the nearby bluff.

Determining its identity will be the job of forensic anthropologist Susan Thurston Myster, a Hamline University faculty member who works with the medical examiner. She examined the skull Monday.

"You can tell quite a bit from the skull," said Thurston Myster. If the skull is modern, its measurements can be entered into a database of known individuals and through comparisons it might be possible to determine its ancestry.

Men's skulls tend to be more robustly constructed, and clues left by neck muscles and the shape of the skull can determine its gender.

Determining the age of the person at the time of death usually depends on the skull's "seams," the lines that mark where skull bones joined together in early life. The seams heal as a person ages, and the state of those seams can point to an age range, although it's likely to be a broad one, said Thurston Myster.

The skull's condition will also point to its age. The skull has not been carbon dated, but Thurston Myster said she hopes to get the money to do so.

"It's not like this happens every day," she said.

Staff writer Steve Brandt contributed to this report. Matt McKinney • 612-217-1747