A tiny discovery on the Mesabi Iron Range this summer has dinosaur-sized implications.

Until recently, precious little evidence existed to suggest the prehistoric beasts ever roamed the area that became Minnesota. But the accidental discovery of a 1¾-inch claw bone is making researchers think twice.

The fully intact claw, thought to be about 90 million years old, is only Minnesota's third piece of dinosaur remains ever documented, experts say. Although paleontologists don't know to what extent dinosaurs made Minnesota home, the finding is significant because it confirms that they were indeed here — renewing hope that there are more fossils yet to be uncovered.

And that could give curators at the Science Museum of Minnesota a new story to tell guests asking about the state's dinosaur past.

"The common line for us to share with visitors was that [evidence of dinosaurs] just doesn't exist here," said John Westgaard, the paleontology research project lead at the St. Paul museum. "[We told kids] 'There's no dinosaur material … the glaciers came through and scraped everything off and it's all gone.' "

The new discovery hasn't yet yielded all its secrets.

Its shape and size indicate that the claw belonged to a theropod, a two-legged carnivorous dinosaur, and a member of the dromaeosaur family. Westgaard said it likely came from a creature similar to the Velociraptor.

A piece of vertebrae and a serrated tooth are thought to be the first dinosaur remains discovered in the state.

"You get put in that mind-set that there aren't any dinosaurs here. Because of the rarity of it, nobody is ever looking for them," said Doug Hanks, a research associate at the science museum who volunteers with the team that found the claw at Hill Annex Mine State Park on Aug. 17.

"If there's a dinosaur tooth and a dinosaur claw, then there's got to be other stuff."

However small, the claw may change the way scientists look at Minnesota's diverse geologic formations.

When dinosaurs roamed the Earth, a seaway extending from the Gulf of Mexico to the Arctic Ocean bisected North America, covering much of Minnesota. The Iron Range was believed to be an estuary system that drained into that seaway, depositing Cretaceous sediments that would later become exposed during mining.

In its heyday, the Hill Annex Mine produced 63 million tons of iron ore for steel. Stockpiles of reddish soil, containing low iron yields, were left behind when work abruptly halted in 1978.

That's where Westgaard, Hanks and their team of volunteers from the museum have scavenged more than 1,300 Cretaceous fossils in the past year. The most common finds include shark teeth, clams, snails and ammonites, or prehistoric coiled shells.

The site, now a state park, has become a draw for history buffs and fossil seekers, said park manager Jordan Schraefer. Tours from Memorial Day to Labor Day provide a detailed history of the mine's contributions to World War II and the opportunity for guests to dig for their own prehistoric treasures.

Visitors' curiosity is also piqued by the seclusion of the park, which lies beyond a locked gate and does not permit visitors to roam unattended due to safety concerns.

While rocks and gems are typically protected at state parks, Schraefer said Hill Annex is an exception because the piles of earth sit on county land. Visitors are free to keep scales, teeth or other fossils they may uncover. Westgaard and Hanks work with summer visitors to document any particularly noteworthy finds that may warrant additional study.

The extraordinary discovery was made on a field crew's last trip of the season.

Volunteer Len Jannusch had been plucking shark teeth from a pile of dirt for a few hours when his back began to hurt from bending over. He decided to take a walk and spotted an unusually shaped fragment near a deer trail. It was the claw bone, sitting right on top of the piles, completely exposed.

"It added a totally different dimension to the project. To be able to say 'dinosaur' changes the game for a lot of people's attention," Westgaard said.

"It was the best Monday ever."

Mother Nature and a potential contract to reopen the mine have given a new urgency to both the paleontology project and park visitors.

Each year, water levels in the area are rising 4 to 7 feet. Scientists estimate that by 2018 much of the Cretaceous strata will be submerged and lost to research.

"Easily within the next five years all of that will be inaccessible," said Hanks, who hopes to keep building the program in the time that's left.

Further complicating matters, plans may be in the works to get the mine running again, which would displace the excavated stockpiles of fossil-rich material. A provision in the law that established Hill Annex as a state park in 1988 says that mineral rights may be reclaimed if the site once again becomes profitable.

But annual rumors that the 625-acre park could close to the public only heighten its appeal, said Schraefer, the park manager.

"The fact that you can take a whole bus of fourth-graders out there, get 'em dirty and give them a tangible educational experience is real important to us," he said. "It fulfills an outreach need that gets them out of the classroom."

The prized claw bone remains under investigation by paleontologists at the museum, who intend to publish a piece about their finding in a scientific journal next year. They hope to have it on display in the next year.

"The idea of digging something out of the ground that's 450 million years old or 90 million years old — and nobody's ever seen that before — is kind of like treasure hunting," Westgaard said. "You have a certain responsibility then to preserve it and put it in a position to be shared by science."

Liz Sawyer • 612-673-4648