For more than 70 million years, it sat preserved underground until last week when the front leg and shoulder of a hadrosaur, a type of duck-billed dinosaur, was dug up in Elk Basin.

While estimates vary depending on the group, to give some perspective on just how long that is, it is speculated that the ancestors of modern humans only arrived about 6 million years ago and modern humans have only been around for about 200,000 years.

The bones were initially discovered around 15 years ago by Marilyn Wagweisner, about 15 miles outside of Powell and a few miles northwest of the gas plant in Elk Basin. Wagweisner was unavailable to talk about her initial discovery in time for press.

Collections manager for the Tate Geological Museum, J-P Cavigelli said Wagweisner had collected a leg, part of the lower jaw, some skull pieces and skin impressions that are currently at the Museum of the Rockies in Bozeman, Montana, and will later be combined with the newly dug up bones.

Now Cavigelli is digging up the remainder of the hadrosaur bones.

There are many different species of hadrosaurs, and this one might be older than others found in Wyoming, Cavigelli said. He estimates their age to be around 70-80 million years old.

“So to me, that means it is a different species,” Cavigelli said.

The Bureau of Land Management contacted Cavigelli in the spring of 2014 and asked if he was interested in collecting the remainder of the dinosaur.

“We applied for a permit and got it quickly, then came here last September for three days, which quickly turned into one day — spent a day cleaning it up and then there was 4 inches of snow, so we decided not to come back out,” Cavigelli said.

He returned this fall with a group of volunteers: longtime volunteer digger, Dwaine Wagoner of Casper, who has helped with several dinosaur excavations in the past, and local volunteers Gerry Johns, Aaron Wilkins and Marynell Oechsner, all of Powell.

Oechsner’s son, Cory Redman, is a paleontologist who led the field camp for the Natural Trap Cave near Lovell. Oechsner was helping out when she met Cavigelli and Wagoner earlier this year, and they mentioned having a dig site nearby.

She went on to recruit Johns and Wilkins as well.

“It’s like a treasure hunt; you just never know what you’re going to come up with next,” Oechsner said.

The lower jaw was unearthed on Thursday, “which is pretty exciting,” Cavigelli said.

Digging for bones is sort of a crapshoot, since underground scanners have mixed results for what’s really buried, and bones tend to move around for various reasons. It’s possible part of the dinosaur was eaten when it died, or shifts in the ground moved or destroyed parts.

“I would be surprised if the whole thing is here, but who knows,” Cavigelli said. “Dinosaur pieces are easy to find, but to find more than just a piece is more difficult.”

Some of the bones were sticking out of the ground when the crew arrived. Although they may look like rocks when only a portion is visible, dinosaur bones have a different shape, texture and appearance from the other rocks.

When alive, and shortly after death, bones have small holes that fill with water when buried. Depending on the mineral content of the water, those holes fill with deposits, similar to how plumbing fills with calcium deposits over time — just on a different scale, Cavigelli said. This is what causes prehistoric bones to look and feel like rocks.

Based on the size of the bones that were found, Cavigelli estimated the hadrosaur was about 30 feet long and stood about 9-10 feet tall at the shoulder. The front leg bone alone weighs about 150-200 pounds.

“That was a pretty big front leg for a hadrosaur,” Cavigelli said.

The bones are too heavy and too fragile to transport back to the vehicles on foot.

The bones were broken into fragments no smaller than a burrito in length, with small cracks throughout. Once exposed, the group coated them with a liquid acetone and plastic, which evaporated quickly so that just plastic was within the cracks to help protect each bone. Once in the lab, the plastic removes easily, Cavigelli said.

Larger fragments were wrapped in plaster for transport.

“We do what a doctor does to a broken leg, wrap it in plaster and burlap,” Cavigelli said.

The bones were sent to Casper, where volunteers in the Tate Geological Museum’s lab will work on them, and they could eventually go on display.

“This is part of the story of what used to be here back in the day,” Cavigelli said. “Dinos get kids interested in the world around them, and the world of the past, and at the same time it gets people interested in how this area got to be what it is.”

The scale of the dig in Elk Basin was big enough that it could be used to figure out what the dinosaur was eating, Cavigelli said.

Dinosaur bones are easier to find in the Rocky Mountains than in other parts of the country because of how the mountains formed: Older layers of dirt got pushed up as mountains rose, and that means more dinosaurs and fossils can easily be found.

If anyone thinks they found dinosaur bones, Cavigelli suggested taking photos and noting the location as accurately as possible with a GPS. Then take the information to the BLM paleontologist in Cheyenne, the local BLM office, or the Tate Geological Museum.

“If fossils are found, they won’t shut ranches down,” Cavigelli said in reference to bones found on private property. “There should be no fear to call the feds.”

(This story has been updated to correct that it is a gas plant at Elk Basin.)