Three years ago, a mounted tyrannosaur skeleton from eastern Montana was shown at an art fair in London as a juvenile Tyrannosaurus rex, with a reported price tag of $20 million. On Oct. 27, 2026, the same skeleton goes to auction at Sotheby's in New York under a different name, Nanotyrannus, with a pre-sale estimate of $6 million to $9 million, according to the auction house's lot listing.

The difference is the science — not the bones. A study published in Nature in October 2025 concluded that Nanotyrannus was a separate animal that lived alongside T. rex, not a teenage version of it. Sotheby's own listing now says the skeleton was misidentified as a juvenile T. rex when it was exhibited at Frieze Masters in 2023.

The sale is now a test of two things at once. One is what the fossil market will pay for a newly validated predator. The other is whether one of only three known Nanotyrannus skeletons will end up somewhere scientists can study it.

From "Chomper" to Jodi

Rancher Jodi Pierson found the skeleton in 2019 on her private land in Garfield County, Montana, near Jordan, in the Hell Creek Formation. Commercial paleontologist Clayton Phipps led the excavation, which was featured in the 2020 Discovery Channel series "Dino Hunters." The fossil passed into a private collection in 2021.

At Frieze Masters in October 2023, the skeleton was presented as "Chomper," a juvenile T. rex. Hypebeast reported that it carried a $20 million asking price at the time. Now it is described as a Nanotyrannus and estimated at less than half that figure. Sotheby's has not publicly explained how it set the estimate.

Sotheby's lists about 191 fossil bone elements from a single animal. They include a skull with 53 bones and roughly 50 teeth, a complete pelvis, a complete wishbone and a complete thighbone. Published descriptions of how complete it is differ. The Associated Press reported about 70%, while other outlets cite an earlier estimate of about 55%. The skeleton measures about 19.6 feet from nose to tail.

The skeleton was unveiled in the lobby of Sotheby's New York headquarters on Oct. 13, NBC New York reported. The sale comes three months after Sotheby's sold a T. rex called Gus for a record $50.1 million.

The Science That Rewrote Its Identity

For decades, paleontologists argued over whether Nanotyrannus fossils, starting with a skull found in 1942, were simply young T. rex. In a Nature study published Oct. 30, 2025, Lindsay Zanno of North Carolina State University and the North Carolina Museum of Natural Sciences and James Napoli of Stony Brook University examined more than 200 tyrannosaur fossils. They concluded that Nanotyrannus was a distinct genus.

The key evidence was in the bones. Growth rings and fused vertebrae showed that a Hell Creek specimen was about 20 years old and nearly mature, so it could not be a juvenile. Compared with T. rex, it had larger forelimbs, more teeth, fewer tail vertebrae, and different patterns of skull nerves. The authors say those traits are set early in development, which rules out a growing T. rex.

"It's not just unlikely, it's impossible," Napoli said of the juvenile T. rex explanation. Reports describe roughly 150 anatomical differences between the two animals.

Size helps explain the difference. Adult Nanotyrannus reached about 18 feet in length, roughly half the length of an adult T. rex, and had slender, blade-like teeth suited to faster prey. Cassandra Hatton, Sotheby's head of science and natural history, compared the pair to "a lion and a cheetah."

A Fight Over Fossils in Private Hands

The sale has sharpened a long-running dispute. Hatton defended commercial collectors, saying the world might not know about Nanotyrannus without them. "These people are crucial in the preservation of science," she said, according to the AP.

Stuart Sumida, president of the Society of Vertebrate Paleontology and a biology professor at California State University San Bernardino, called that argument a "blatant lie." "No peer-reviewed scientific study can be published on specimens that are not held in the public trust," he said. The society has called for significant fossils like Jodi to go to museums and research institutions instead of private buyers.

The issue is practical — not just philosophical. Many journals, following Society of Vertebrate Paleontology standards, require fossils described in a study to be held in a permanent public collection so other researchers can check the results. A skeleton in a private home can drop out of science entirely. Both sides of this debate have a financial or institutional interest in how fossils are sold and collected.

The legal setting matters too. Fossils found on private land in Montana belong to the landowner and can be sold. Vertebrate fossils on federal land generally cannot be collected without a permit and must stay in public repositories. That split is why so many Hell Creek specimens reach the market.

A Follow-Up Comes After the Hammer Falls on Oct. 27

Several questions remain open until the sale. Sotheby's has not said whether any museums have registered to bid. The buyer's identity may never be disclosed, and the hammer price could land well above or below the estimate. Recent dinosaur sales, including a juvenile Ceratosaurus that sold for more than five times its high estimate in 2025, show how unpredictable these auctions can be.

The other two known Nanotyrannus skeletons are already in public hands. One is part of the "Dueling Dinosaurs" fossil at the North Carolina Museum of Natural Sciences, and the other is at the Burpee Museum of Natural History in Rockford, Illinois. Readers who want to see the animal up close can visit those collections.

Nature World News will report the sale result and any information about the buyer after the Oct. 27 auction.

The bottom line: a change in the science cut this skeleton's market value by more than half and gave it a new name. Whether its next home is a museum or a private collection will decide whether researchers can keep studying it.

What Readers Want to Know

What is being auctioned?

Jodi, a mounted Nanotyrannus skeleton about 67 million years old, found in 2019 on private land in Garfield County, Montana.

When is the sale and what is the estimate?

Sotheby's New York, Oct. 27, 2026, with an estimate of $6 million to $9 million.

Why was it once called a T. rex?

Many scientists treated Nanotyrannus fossils as juvenile T. rex until a 2025 Nature study found they belonged to a separate, adult animal.

How is Nanotyrannus different from T. rex?

It was about half the length, with larger forelimbs, more teeth, fewer tail vertebrae, and different skull nerve patterns.

Why do paleontologists object to the sale?

Fossils in private collections usually can't be studied or used in peer-reviewed research, so a private sale could remove the specimen from science.

Where can I see a Nanotyrannus in person?

The North Carolina Museum of Natural Sciences and the Burpee Museum of Natural History in Rockford, Illinois.