Billed as a miracle of nature and a masterpiece, this is Big John - the largest triceratops ever discovered on Earth.

At more than 66 million years old and with an 8m-long skeleton, it is now being prepared for the public eye from Sept 16 in Paris, ahead of its auction at Hotel Drouot next month. It is expected to fetch up to €1.5 million (S$2.4 million).

One of the giants of the Cretaceous period, the dinosaur lived in Laramidia, an island continent that once stretched from what is now Alaska to Mexico, and died in an ancient flood plain now known as the Hell Creek rock formation in South Dakota.

Palaeontologists unearthed the first piece of bone in 2014 and eventually found 60 per cent of its skeleton, including a near-complete skull.

Big John was named after the owner of the land where the dinosaur's bones were found. A laceration on the collar suggests the dinosaur was injured in combat with another triceratops, probably in defence of territory or a mate.

The triceratops is among the most distinctive of dinosaurs due to the three horns on its head - one at the nose and two on the forehead.

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 Mr Alexandre Giquello, who is leading the sale.

Some of them are people passionate about science and palaeontology.

"They are often quite young, coming from new technologies; they are in fact the Jurassic Park generation. They have seen the movies and have been immersed in this Hollywood mythology," he is quoted by The Guardian as saying.

Last October, a rare allosaurus skeleton, one of the oldest dinosaurs and considered to be the "grandfather" of the T-rex, was sold in Paris to an anonymous bidder for a little over €3 million, twice the estimate.

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