A Tyrannosaurus rex skeleton recently sold for an astronomical price: nearly $32 million, a record for a fossil. The 67 million-year-old dinosaur, nicknamed Stan, is one of the largest and most complete T. rex skeletons ever found. Stan measures 13 feet high and nearly 40 feet long.

The enormous fossil was sold at an auction to an anonymous bidder—and that worries many scientists. Their dino-sized concern? That the prehistoric specimen will land in a private collection and be lost to science.

Stan is named for an amateur paleontologist who found part of the skeleton in South Dakota in 1987. Until recently, the dinosaur had been on display at the Black Hills Institute of Geological Research in South Dakota, where it was studied for years by experts from around the world.

Research on the T. rex skeleton has revealed important insights about the species, including how the animals moved and the force of their bites. Experts have also found evidence that Stan got into some nasty fights. For example, its fossilized skull sports an inch-wide hole that suggests the dinosaur was bitten by another T. rex—and managed to heal.

Researchers fear that Stan’s new owner will keep the fossil in a private collection where scientists may not be allowed to study it (and where the public may be prevented from viewing it). Experts are also concerned that if private collectors continue to drive up fossil prices, museums won’t be able to afford to buy them. Some scientists are calling for laws to preserve fossils found on private land—as Stan was—for scientific research.