One of Colorado's most astonishing and coincidental fossil discoveries was found earlier this year, right beneath the parking lot of the Denver Museum of Nature & Science, museum officials announced last week.

While drilling for a geothermal tap in January, museum scientists decided to take the opportunity to study what lay below the surface. To their surprise, they hit something unexpected: a dinosaur bone.

Patrick O'Connor, director of Earth and space sciences at the museum, recalled the moment vividly.

"He said, 'there's a fossil in the core,'" O'Connor said. "Really?"

What makes the discovery so improbable is how precisely the fossil had to be struck. Crews had to drill in just the right spot, at just the right depth, and then puncture the bone with a core bit only a couple of inches wide.

"In the mud was this," O'Connor said, referring to the sample. "It looks like a piece of dinosaur bone."

Regardless of its appearance, researchers confirmed that it's the oldest and deepest fossil ever found in Denver.

"Given the age of the rocks where this was found, it's estimated to be about 67 million years ago," O'Connor said. "There were not a number of large animals on the surface of the planet at that time other than dinosaurs."

"In my 35 years at the museum, we've never had an opportunity quite like this, to study the deep geologic layers beneath our feet with such precision," said Earth Sciences Research Associate Bob Raynolds. "That this fossil turned up here, in City Park, is nothing short of magical."

Although scientists don't yet know which specific species it belonged to, they've narrowed it down to a group of plant-eating dinosaurs based on the bone's structure.

"The bones that make up their backbone are constructed differently," O'Connor said. "So even though we can't tell you all of the details about it just by looking at the structure of the bone, we know it pertains to one group of plant-eating dinosaurs."

The fossil is now on display in the museum's "Teen Rex" exhibit.

"Everyone can discover," O'Connor said. "Everyone can participate in science."