Largest stegosaurus skeleton ever found that stretches 27ft long after fossil hunter stumbled across it during a birthday stroll in a town called Dinosaur is set to sell for up to $6million

The largest stegosaurus skeleton ever found that stretches a staggering 27ft long is set to sell for up to $6million after a fossil hunter stumbled across it during a birthday stroll in a town called Dinosaur.

Jason Cooper discovered part of the bone formation sticking out of a rock wall located on his Dinosaur, Colorado property on his 45th birthday in May 2022.

He began excavating the site and cleaning the bones with the help of some friends.

'We looked around. My friend found some vertebrae. I said, 'Oh my gosh, this is turning out to be a really great birthday!'' he told BBC News.

The fossil hunters recorded as much data as they could about where the fossils were found and relocated them back to Cooper's dino-shop where they began working on assembling the skeleton - which he named Apex.

Former digs on Cooper's property have yielded a number of Jurassic period dinosaurs - several of which the fossil hunter has donated to institutions including the Brigham Young University Museum of Paleontology in Provo, Utah, and the Forest Museum of Science in Miami. 

But Cooper knew instantly that Apex was an impressive find, with the dinosaur remains standing at an incredible 11.5ft tall, spanning around 27ft long, nd 6ft wide, at just 70 per cent completion.

The dinosaur enthusiast described the Apex stegosaurus as a unique and specifically important specimen as skeletons - even partial ones - of the plate-backed, spike-tailed herbivore are rare. 

However, the lucky fossil enthusiast was even more stunned when he learnt that Sotheby's believes the find, which had been buried underground for 150milion years, could fetch up to $6million at auction.

Cooper's stegosaurus is still only 'virtually complete' but the bones have been well preserved, with the impressive 247 pieces mounted on a steel armature, Sotheby's said in a press statement.

Apex is about to become the first stegosaurus to go under the hammer at auction. 

According to Cassandra Hatton, the auction house's global head of science and popular culture, the skeleton is 'one of the best fossils of its kind ever unearthed'.

She also said: 'Nobody ever found 100% of a dinosaur. 

'A stegosaurus as good as this is hard to find, I think it's going to be incredibly important.

'Even impressions of the skin have been preserved.' 

Apex is set to be auctioned off for around $4million to $6million on July 17 during Sotheby's annual 'Geek Week' sale in Manhattan, with the company describing the piece was one of the 'most valuable dinosaur fossils ever offered'.

The highest bidder will receive a copy of the dinosaur's scan data, plus a full license to use any 3D data however they choose.

This, according to Sotheby's, 'will allow primary information about the dinosaur to remain with the specimen and promote collaboration in future research and education.' 

Bidding is expected to be brisk with dinosaur fossils having become a desirable addition to the properties of tech moguls and Hollywood stars.

This is sad news to paleontologists who claim that allowing the fossils to end up in private hands interrupts scientific research and keeps them hidden from the public.

Steve Brusatte, a professor of paleontology at the University of Edinburgh, told CNN that Apex belongs in a museum.

'It is a great shame when a fossil like this, which could educate and rouse the curiosity of so many people, just disappears into the mansion of an oligarch,' he told the news outlet.

It was reported in 2019 that celebrities including Leonardo DiCaprio, Russell Crowe, and Nicolas Cage were among the famous people who have purchased prehistoric remains.

Nicolas Cage reportedly purchased a tyrannosaurus skull for more than $236,000 in 2007 after a bidding war with Leonardo DiCaprio, though he returned it after it came to light that it had been stolen.

Cooper's stegosaurus was discovered in the Morrison Formation in Colorado - a vast stretch of sedimentary rock dating back to the Jurassic period.

The area is known for being a rich source of dinosaur fossils, according to the National Park Service. 

The Morrison Formation is centered in Wyoming and Colorado, with outcrops in Montana, North Dakota, South Dakota, Nebraska, Kansas, the panhandles of Oklahoma and Texas, New Mexico, Arizona, Utah, and Idaho. 

Apex took over a year to fully excavate and was found to have signs of arthritis - suggesting to experts it had lived to an old age, but also showed no signs of combat or predation-related injuries.

Visitors to Sotheby's New York galleries will be able to see Apex as part of a free exhibition of some of the items on sale during Geek Week, before they are handed over to their buyers.

Sotheby's 'legacy of pioneering Natural History auctions' includes the 2022 sale of a Gorgosaurus skeleton, which sold for just over a huge $6million.

It also sold the first standalone T-Rex skull with 'Maximus' in December of the same year.

The world's most complete Tyrannosaurus rex skeleton, Stan, set a new world record in 2020 when it sold for $3.18 million at Christie's.

Stan was discovered in South Dakota in 1987 and was named after the amateur paleontologist who came across the remains, Stan Sacrison.

The remains were initially thought to be of a triceratops, but a further analysis in 1992 showed its true identity as a T-Rex.

The skeleton includes 188 bones, making it 70 percent complete, however, its skull is the most complete and preserved found to date.

The skeleton vanished from the public eye when an anonymous bidder paid the record-breaking amount.

At the time, paleontologists feared the fossil was lost to science, but in March the Abu Dhabi Department of Culture and Tourism revealed plans for Stan to be the latest attraction at a new museum of natural history, expected to open in 2025 in Abu Dhabi.

In the UK fossil hunters are generally allowed to keep small finds including shells and corals but must report larger, and more historically significant finds.

In the US, however, there are no such restrictions, meaning anyone who digs up a dinosaur on their own property had full ownership of it and can do with it as they please.