A T. rex skeleton which was expected to fetch up to $25m at auction has been withdrawn after doubts were raised over where parts of it had come from.

It said the seller had decided to loan the skeleton to a museum instead. Christie’s did not give a reason why the sale had been withdrawn. The New York Times report that a US fossil company raised concerns that parts of the skeleton, named Shen, looked like replicas from another T. rex skeleton called Stan.

The Black Hills Institute holds the intellectual property rights to Stan, meaning it is allowed to sell replicas, with casts costing $120,000.

However, its president, Peter Larson, told the NYT that parts of Shen looked similar to parts of Stan. When he saw photos of Shen, he told the newspaper, he noticed the skull looked like Stan’s, and said it had similar, unique holes in its jaw.

Mr Larson told the newspaper that he thought Shen’s owner – who has not been identified – had bought a Stan replica and used the bones to complete the Shen skeleton. “They’re using Stan to sell a dinosaur that’s not Stan,” Mr Larson said in an interview with the outlet before the sale was called off. “It’s very misleading.”

The newspaper reports Mr Larson said Christie’s had “done the right thing” in calling off the auction. It says a lawyer for Mr Larson contacted Christie’s, saying that the auction house had not made clear that parts of the skeleton were casts from Stan.

After this, the newspaper reported, the online listing was changed to read: “Replica bones that were added to original bones (referred to as STAN™ elements) were created by, and purchased from, Black Hills Institute of Geological Research, Inc.”

Shen, which weighs 1.4 tonnes, and is 4.6m (15ft) tall and 12m long, was discovered in the US state of Montana and is thought to have been an adult male who lived around 67m years ago.

He was estimated to fetch between $15m and $25m had he gone up for sale. Stan was auctioned by Christie’s in 2020 and went for $31.8m.

Sales of dinosaur bones can rake in millions, but have been criticised by experts who say they often end up in private collections, away from researchers.