The Largest Stegosaurus Fossil Ever Found Could Fetch $6M at Sotheby’s

The virtually complete skeleton will go on the block next month alongside a copy of its scan data.

Large dinosaur skeleton pictured against black background
Apex is the largest Stegosaurus fossil ever found. Photo: Matthew Sherman/Courtesy Sotheby's

The Stegosaurus, a spike-tailed herbivore species that roamed the earth during the Late Jurassic period, is perhaps the best-known of the armored dinosaurs. Now, the largest and most complete fossil Stegosaurus specimen ever unearthed is hitting the auction block two years after its accidental discovery in Colorado’s Morrison Formation.

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Nicknamed “Apex” for both its size and significance, the 150-million-year-old fossil measures eleven feet tall and twenty feet long and is 30 percent larger than the Stegosaurus fossil “Sophie,” which is held in London’s Natural History Museum and was previously the most complete example of the species. It is expected to realize between $4 million and $6 million next month when it stars in Sotheby's live Natural History auction on June 17.

The fossil was discovered in May of 2022 on the private land of Jason Cooper, the commercial paleontologist who founded the Trilobites of America lab and is co-owner of the Dinosaur Corporation, which supplies replica fossils to museums and scientific institutions. He stumbled upon Apex’s femur while walking around his property in Moffat County, Colorado, near the aptly named town of Dinosaur. The fossil was excavated in 2022 and 2023. Cooper has previously donated several specimens found on his land to institutions around the globe, according to Sotheby’s.

Dinosaur fossil tail with four spikes pictured against black background
The Stegosaurus is the best-known of the armored dinosaurs. Photo: Matthew Sherman/Courtesy Sotheby's

The practice of auctioning off dinosaur skeletons has inspired mixed reactions in the world of academic paleontology, with some experts arguing that the high price tags associated with such rare specimens renders them inaccessible to research institutions and museums. The 2022 sale of a Gorgosaurus skeleton, for example, saw the fossil acquired at Sotheby’s by a private buyer for $6.1 million; the same amount was shelled out by an anonymous buyer for a Tyrannosaurus rex skull offered up by the auction house later that year.

In some cases, collectors do acquire dinosaur fossils at auction with the intention of donating them to an educational institution. In 1977, Sotheby’s auctioned off “Sue” the T. rex, the first dinosaur ever sold at auction, for $8.4 million. Financed by private individuals and corporations like the McDonald’s Corporation, Ronald McDonald House Charities, Walt Disney World Resort and the California State University System, the winning bid was made by Chicago’s Field Museum of Natural History. In 2020, another T. rex named “Stan” was acquired for $31.8 million by Abu Dhabi’s Department of Culture and Tourism, which will display the fossil—the most expensive dinosaur ever sold—in the Natural History Museum Abu Dhabi upon its completion next year.

Apex’s winning bidder will also receive valuable data

As opposed to any evidence of combat or predator-related injuries, Apex displays signs of arthritis and likely lived to an “advanced age,” according to Sotheby’s. The virtually complete specimen has 247 fossil bone elements and will be sold with additional 3D-printed elements informed by the skeleton. To boost transparency and promote further research and education, the winning bidder will also receive a copy of the dinosaur’s scan data and a full license to utilize that data for scans, molding and any other purpose they see fit.

Sotheby’s claims its auction is the first example of an auction house collaborating on the sale of a dinosaur skeleton from discovery, as it worked alongside Cooper to document the fossil’s unearthing, restoration and mounting. “Apex marks an incredibly important milestone, as simply one of the best fossils of its kind ever unearthed,” said Cassandra Hatton, Sotheby’s global head of science and pop culture, in a statement. “Through the careful process of excavation, preparation and installation, Apex sets a new standard for all future discoveries of this magnitude, and further reinforces the enduring appeal of Stegosaurus and its vaunted status in popular culture.”

The Largest Stegosaurus Fossil Ever Found Could Fetch $6M at Sotheby’s