The buyer who spent a record $44.6 million to buy a stegosaurus fossil at auction was Ken Griffin, CEO of the Citadel hedge fund, according to a person familiar with the acquisition.

The skeleton, nicknamed Apex, is estimated to be 150 million years old and is the largest stegosaurus ever found, according to the auction house.

Griffin placed his bid over the phone to beat six others in a 15-minute-long bidding war on Wednesday, a live audience cheering as the price jumped.

"Apex was born in America and is going to stay in America," he said after the sale, according to The Wall Street Journal, which broke the news that Griffin was the buyer.

A regular donor to the Republican party, the hedge fund chief has a net worth of approximately $37.8 billion, according to Forbes.

He intends to explore loaning the specimen to a US institution, the source told AFP.

The executive has collaborated with museums in the past. In 2021, he paid $43.2 million for a first-edition copy of the US Constitution, later loaning it to the Crystal Bridges Museum of American Art in Arkansas.

He also helped fund a dinosaur exhibit at Chicago's Field Museum in 2018 with a $16.5 million donation.

His latest purchase measures 11 feet (3.3 meters) tall and 27 feet (8.2 meters) long, and is near complete, with 254 bones out of an approximate total of 319.

Dinosaur remains have become a hot-ticket item in recent years, with paleontologists voicing concern that museums are losing out to private bidders.

The previous record for a dinosaur skeleton sale was set in 2020, when a Tyrannosaurus Rex nicknamed "Stan" went for $31.8 million.

Apex is 30 percent larger than "Sophie", the most complete stegosaurus ever put on public display, which is housed in the Natural History Museum in London.