Sotheby’s sold a Tyrannosaurus rex fossil at auction on Tuesday for $50.1 million, with fees, topping records set in recent years amid a surging market for prehistoric specimens.

The towering skeleton, nicknamed Gus, was sold after a nearly 10-minute bidding war. The auction house declined to name the buyer, or even reveal the person’s location.

“Try a bigger bite,” said Phyllis Kao, an auctioneer at Sotheby’s about seven minutes into the sale that included seven competing bidders. “It’s a T. rex after all.”

The sale allowed the T. rex to reclaim its title as the most valuable on the commercial fossil market. Two years ago, it had been unseated — by an herbivore, no less — when a stegosaurus fossil was auctioned for $44.6 million.

The record continues a trend of climbing prices for dinosaur bones, which has delighted commercial fossil hunters while drawing criticism from paleontologists at universities and museums who worry that they are being priced out of the market.

The 12-and-a-half-foot-tall T. rex fossil was excavated from private land in fossil-rich South Dakota in a multiyear process that started in 2021. At that time, the fossil industry had just been supercharged by the sale of another T. rex skeleton — known as Stan — which sold for $31.8 million, driving fantasies of buried treasures out West.

The winning bid was taken by Cassandra Hatton, a Sotheby’s executive, who said in a statement after the sale that “Gus is not only an exceptional find but a specimen that’s been excavated, documented, prepared and cared for with real excellence.”

Many paleontologists balk at the private sale of scientifically valuable specimens because they believe that the fossils should be owned by an accredited museum, university or government collection to ensure that research can be performed and tested in the future.

Ahead of Tuesday’s sale, the Society of Vertebrate Paleontology cautioned in a news release that when private individuals buy fossils, “opportunities for future research, education and public engagement may be permanently diminished.”

The sale in New York, part of what Sotheby’s has named “Geek Week,” included trilobite fossils from Morocco, marine reptile fossils from Germany and a “baby dinosaur nest” discovered in Montana.

But the star of the sale was Gus, which was named after Gary Licking, the owner of the land in South Dakota where the specimen was found. Licking had long been stumbling upon small bone fragments on his 6,500-acre cattle ranch when he decided to partner with a commercial paleontologist to mount a search for fossils. Licking, known as Gus, died in 2022, not long after the bone hunters began excavating the specimen.

The commercial paleontologist Thomas Heitkamp and his team excavated the T. rex bones over three summers. They spent several more years in the laboratory, where the fossils were extracted from a huge matrix of rock and assembled into the 38-foot-long apex predator, with its small arms, powerful tail and terrifying jaws.

Sotheby’s says that elements of 183 bones of the specimen were found, meaning that other bones had to be fully reconstructed. (There are no complete T. rex skeletons; some scientists have estimated that a complete specimen has about 300 bones, while others have gone higher.)

The remains of Gus, who walked the earth about 67 million years ago, include healed rib bones and a skull that had possibly been gnawed on by scavengers, the auction house said. Unique evidence of wounds or disease are valued in the fossil market, often leading to higher prices.

Tensions between the commercial and academic sides of paleontology escalated after Stan was sold in 2020. Its buyer was initially anonymous, stoking fears that the scientifically significant specimen would disappear into a billionaire’s mansion. It eventually emerged that Stan had been bought for the developing Natural History Museum Abu Dhabi, in the United Arab Emirates, which opened late last year with the 13-foot-tall Stan as its centerpiece.

The eye-popping sales kept coming, even for dinosaurs lower on the food chain.

In 2022, a fossilized Deinonychus antirrhopus (like the clawed, bipedal creatures in “Jurassic Park”) sold at auction for $12.4 million. Two years later, the sale of an unusually complete stegosaurus shattered the record set by Stan. And just last year, a juvenile Ceratosaurus, a carnivorous reptile, sold for $30.5 million.

“It’s a new world,” said Peter Larson, a commercial paleontologist from South Dakota whose team excavated Stan in the early 1990s. “People are just now realizing their real value.”

In defense of the fossils’ high price tags, Larson cited the years of painstaking work it takes to excavate and prepare a specimen for sale.

But many academic paleontologists balk at the glamorization of owning a fossil like a piece of art, a trend among celebrities and the ultra wealthy.

“The auction houses are in a competitive race to sell the most expensive dinosaur ever,” said Thomas Carr, a paleontologist at Carthage College in Wisconsin. “No museum could afford this.”

In marketing materials, auction houses often compare their specimens with other famous fossils (Sotheby’s noted to potential buyers that Gus’s femur length of 50.39 inches is “larger than that of Stan”). Even before the specimen sold, Sotheby’s advertised it as the “most valuable dinosaur offered at auction,” based on the auction house’s estimate that it would sell for $20 million to $30 million.

Amid a flourishing commercial fossil market, there have been bumps in the road. In 2022, Christie’s withdrew a T. rex fossil from auction after accusations that marketing materials had made the skeleton seem more complete than it was.

Some wealthy buyers have tried to prove that academic institutions can still benefit from the commercial side of the industry.

After Kenneth C. Griffin, the hedge fund billionaire, set a record with his $44.6 million purchase of the stegosaurus known as Apex in 2024, the American Museum of Natural History in New York began displaying it as part of a four-year loan. Griffin’s loan included funding for researching and documenting the specimen, including 3-D scans of the fossilized bones that the museum says it will make accessible to researchers.