For decades, Tyrannosaurus rex has occupied a unique place in popular culture, appearing as both a scientific subject and a symbol of prehistoric power. Now, one exceptionally preserved specimen has made history for a different reason: its price.

Private buyers are increasingly outbidding museums for fossils. That’s making it difficult—or even impossible—for researchers to improve our understanding of the past.

A Tyrannosaurus rex skeleton from South Dakota, nicknamed Gus, has become the world’s most expensive fossil sold at auction.