$44.6 million stegosaurus fossil will go on display this weekend at NYC's American Museum of Natural History

An immense stegosaurus skeleton, the most expensive fossil ever sold at auction when billionaire Kenneth Griffin bought it this summer for $44.6 million, will go on display this weekend at New York City’s American Museum of Natural History.

Museum officials said at an unveiling Thursday in Manhattan that the 27-foot-long, 11-foot-high skeleton — dubbed Apex — was thought to be one of the largest and most complete specimens ever uncovered of the stegosaurus, a plant-eating giant characterized by bony back plates and a mace-like spiked tail that lived during the Late Jurassic period 150 million years ago.

“It contributes a lot to our understanding of what a large individual looks like in a way that other stegosaurus fossils haven’t,” said Roger Benson, the museum’s curator of paleontology, in an interview.

The specimen will be on loan for four years, and hedge funder Griffin, who previously donated $40 million to the museum, will permit its scientists to take a small sample of thigh bone for the museum’s permanent collection. That sample, along with three-dimensional digital models of the skeleton, will form the basis of research that will identify Apex’s species, produce a stegosaurus growth curve and investigate skeletal changes in the stegosaurus as it grew from juvenile to adult, according to the museum.

Scientists know of fossils for only 80 stegosaurus individuals found in the last 150 years, Benson said, and many of those finds are “very incomplete,” consisting of just one bone or fragment of a skeleton. Apex, however, included more than 254 of approximately 320 bone elements when a commercial paleontologist, Jason Cooper, found it in 2022 on land he owned outside the tiny town of Dinosaur, Colorado.

Like most dinosaur fossil discoveries, this one was decidedly low-tech, Benson said. “Generally one finds fossils by seeing some bones sticking out of the ground, the problem being that once there are bones sticking out of the ground, that means the surface has been eroded, and you’re always missing a few bones.”

The stegosaurus has been unfairly maligned as having a brain the size of a walnut. In truth, its brain was probably closer in size to a lemon, Benson said.

Apex would have weighed 3-5 tons, judging by the size of its four limb bones, he said. Its relatively short feet probably indicate that Apex was not a galloping animal. Its overall size and the 5-foot-long spikes protruding from its tail probably indicate that it did not need to move fast anyway. “A big old individual like this was probably capable of looking after itself,” Benson said.

That land where Apex was found was part of the Morrison Rock formation, whose sedimentary rock covers much of the western United States. Its ancient river channels and floodplains are the richest source of dinosaur bones in North America. Its fossil record suggests that Apex inhabited an ecosystem with giant conifers, ginkgos, small mammals and an array of other dinosaurs, but little is known about how Apex lived and died. “We don’t see marks on the bones that would suggest that a predator killed it,” Benson said. “We don’t have evidence of their eggs and nests.”

Some paleontologists have criticized fossil sales like the Apex auction this summer, arguing that specimens belong in museums or research centers which often can’t afford huge auction prices.

“I don't think fossils should be allowed to be auctioned,” Cary Woodruff, curator of vertebrate paleontology at Miami’s Frost Museum of Science, told NPR in a July interview. If wealthy collectors do buy them, Woodruff said, they should consider donating the originals and keeping replicas.

George Winters, administrative director of the Association of Applied Paleontological Sciences, whose membership consists primarily of commercial paleontologists who buy and sell fossils, said that concern was misplaced in this case.

After the auction, “Statements were put out there that now this is lost to science — obviously this isn’t lost to science. The gentleman who purchased it loaned it to the (museum), where there’s a chance to study it.”

A spokeswoman for Citadel, Griffin’s investment firm, said in emails that Griffin bought Apex with the intention of loaning the specimen to a museum and would likely loan it to other museums.

Paul E. Olsen, a paleontologist at Columbia University's Lamont-Doherty Earth Observatory, said most collectors would encourage exhibition and study of their specimens, if only because the attention tends to increase their value. Besides, he said, “it’s virtually impossible to get grant funding to excavate or look for dinosaurs like stegosaurus or T. Rex — the effort is very large and your chance of success… is not great. If a commercial collector didn’t collect this specimen, nobody would and eventually it would decay to nothing.”

Olsen said it was unlikely that Apex would revolutionize paleontologists’ knowledge of the stegosaurus, already one of the most studied dinosaurs. “But that may not be where its greatest value lies,” he said. “It’s awesome, and anything you can do, anything an institution like a museum can do, to strike awe and wonder in people, is absolutely worth it.”

Apex will stay through next summer in the Kenneth C. Griffin Exploration Atrium before moving to the fourth floor, where museum president Sean Decatur said it would become the centerpiece of a new exhibit.