THORNTON, Colo. (CBS4)– It was nearing the end of summer when an inspector at a Thornton construction site noticed something out of the corner of his eye. Something that looked to be the size of a quarter turned out to be much, much bigger and from a different time.

Dan Wagner was inspecting new concrete at the site as August was winding down when the object caught his attention.

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CBS4’s Stan Bush interviews Dan Wagner (credit: CBS)

“I was just looking at chunks of this bedrock and I looked down and I saw something way different … it was dark brown,” said Wagner, an inspector with Terracon Consultants.

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Wagner brushed the ground with his boot and wanted to make sure what he found wasn’t a fluke, “So I grabbed a shovel and started digging around and I heard the ‘Clink, clink’ of the shoulder blade bone … it was four inches wide and that’s when I called the supervisor.”

The crews were working to build a new public safety facility for the City of Thornton near 132nd and Quebec when all work came to an abrupt halt on Aug. 25. Construction workers gawked at what had been found.

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“Right away, the initial reaction they had was, ‘Wow look at that, that really could be a dinosaur,'” said Wagner.

Scientists with the Denver Museum of Nature and Science inspected the find and said the bones belonged to a triceratops, a rare one.

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“They thought it was a bone, called out experts from the Denver Museum of Nature and Science and they say ‘Most likely dinosaur bones, pretty certain,'” said Todd Barnes with the City of Thornton.

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One bone became a handful and soon dozens emerged, to the point where almost every time paleontologists put a shovel into the ground a new fossil popped out.

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“It’s starting to look like most of a skull is taking place,” said DMNS Curator of Dinosaurs Dr. Joe Sertich.

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“We’re missing all of the limbs, the hind legs, they’re probably around here somewhere,” said DMNS Paleontologist Dr. David Krause.

Construction crews could have easily bulldozed over all of the find but instead they jumped in to pull history out of the ground.

“This is the kind of find that makes everybody stop and take notice and get serious about preservation efforts,” said Barnes.

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DMNS experts says the fossil could be as much as 66 million years old. The triceratops is one of the last dinosaurs to walk the Earth. The find in Thornton is one of the most complete discoveries ever from that time.

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“It’s an iconic, popular dinosaur. Most kids know it — with big horns over its eyes, a little nose horn and a shield on the back of its head,” said Sertich.

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The museum said when the triceratops is finished being cleaned and reassembled, the crew that found it will have their names next to it, commemorating their role in uncovering history.

When asked if any of this has sunk in yet, Wagner replied, “No, it hasn’t sunk in. Maybe one day when it gets all set up and the skeleton is all in the display case and it’s all set up as a whole.”

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CBS4 is a proud partner of the Denver Museum of Nature and Science on the Thornton triceratops discovery. Watch CBS4 News for exclusive stories from reporter Stan Bush and photojournalist Mark Neitro at the dig site and in the museum’s lab.