Big John, named after the owner of the land where the dinosaur’s bones were found, roamed modern-day South Dakota more than 66 million years ago.

“It’s being acquired by an American collector, who is absolutely thrilled with the idea of being able to bring a piece like this to his personal use,” said Djuan Rivers, a representative for the buyer.

The first piece of bone from the supersized skeleton, its skull alone 2.6m long and 2m wide, was found in 2014.

By 2015, paleontologists had unearthed 60% of the skeleton, a rare feat, made of over 200 pieces painstakingly put together in Italy to prepare for the Paris auction.

The skull showed a traumatic lesion, which researchers said was likely the work of another triceratops striking it from behind.

“The history behind this and the curation of it is absolutely impressive, so to be able to be a part of preserving something of this nature that was actually found in the US is also something extremely special,” Rivers said.

The name triceratops means “three-horned face”.

The hammer price at the Drouot auction house, before commission and other costs, was €5.5 million. Drouot had estimated the skeleton would fetch between €1.2 million and €1.5 million.

“It’s a record for Europe,” said auctioneer Alexandre Giquello, who described exponential growth in the relatively new market of dinosaur fossils. “We’re creating a market.”