It came from a hole drilled more than 230 metres deep to study geothermal heating potential for the Denver Museum of Nature and Science.

The museum is popular with dinosaur enthusiasts of all ages.

Full-size dinosaur skeletons amaze kiddos barely knee-high to a parent, much less to a Tyrannosaurus.

This latest find is not so visually impressive. Even so, the odds of finding the hockey-puck-shaped fossil sample were impressively small.

With a bore only five centimetres wide, museum officials struggled to describe just how unlikely it was to hit a dinosaur, even in a region with a fair number of such fossils.

“Finding a dinosaur bone in a core is like hitting a hole in one from the moon. It’s like winning the Willy Wonka factory. It’s incredible, it’s super rare,” the museum’s curator of geology James Hagadorn said.

Only two similar finds have been noted in bore hole samples anywhere in the world, not to mention on the grounds of a dinosaur museum, according to museum officials.

A vertebra of a smallish, plant-eating dinosaur is believed to be the source. It lived in the late Cretaceous period around 67.5 million years ago.

An asteroid impact brought the long era of dinosaurs to an end around 66 million years ago, according to scientists.

Fossilised vegetation also was found in the bore hole near the bone.

“This animal was living in what was probably a swampy environment that would have been heavily vegetated at the time,” said Patrick O’Connor, curator of vertebrate paleontology at the Denver Museum of Nature and Science.

Dinosaur discoveries in the area over the years include portions of Tyrannosaurus rex and triceratops-type fossils. 

This one is Denver’s deepest and oldest yet, O’Connor said.

Other experts in the field vouched for the find’s legitimacy but with mixed reactions.

“It’s a surprise, I guess. Scientifically it’s not that exciting,” said Thomas Williamson, curator of paleontology at the New Mexico Museum of Natural History & Science in Albuquerque.

There was no way to tell exactly what species of dinosaur it was, Williamson noted.

The find is “absolutely legit and VERY COOL!” Erin LaCount, director of education programs at the Dinosaur Ridge track site just west of Denver, said by email.

The fossil’s shape suggests it was a duck-billed dinosaur or thescelosaurus, a smaller but somewhat similar species, LaCount noted.

The bore-hole fossil is now on display in the Denver Museum of Nature and Science, of course, but there are no plans to look for more under the parking lot.

“I would love to dig a 233-metre hole in the parking lot to excavate that dinosaur, the rest of it. But I don’t think that’s going to fly because we really need parking,” Hagadorn said.