Big John roamed the lands of modern-day South Dakota in the United States more than 66 million years ago. Paleontologists unearthed the first piece of bone in 2014 and eventually found 60% of his skeleton, including a near-complete skull.

The Drouot auction house estimated Big John’s skeleton would fetch €1.2-1.5 million. Once primarily sold to museums, dinosaur remains have increasingly attracted private buyers, though their numbers remain few.

“I imagine there are about 10 buyers worldwide for this kind of piece,” said Alexandre Giquello, who is leading the sale.

The skull of Big John, named after the owner of the land where more than 200 of the dinosaur’s bones were found, is 2.62m in length – nearly a third of his overall body length – and 2m wide.

The name triceratops means “three-horned face”. In the fossilised remains of his bony frill is a gaping hole, a battle scar inflicted by a smaller rival, according to paleontologist Iacopo Briano.