Long, long ago, two dinosaurs died apparently locked in a battle on the plains of modern-day Montana. Today, a battle over who owns the entangled fossil has turned into a multimillion-dollar issue. The outcome hinges on the legal definition of what constitutes a “mineral.” The Dueling Dinosaurs fossil is valued between $7 and $9 million.

Years ago, Lige and Mary Ann Murray bought a fossil-rich land parcel in eastern Montana from George Severson. His sons, Jerry and Robert Severson, were part owners. According to a 2005 contract, the brothers sold their “surface rights” to the Murrays. But they retained some of the “mineral rights.”

At the time of the sale, neither party suspected that there were valuable fossils buried on the ranch. But a few months later, an amateur paleontologist discovered the remains of the carnivore and herbivore grappling.

When the Seversons heard about the find in 2008, they sought to lay partial claim to the fossilized remains. The Murrays also asked for a court order giving them ownership.

If the private battle wasn’t enough, scientists want a voice in it too. By law, fossils found on private property can be privately owned. Paleontologists claim that vast historical resources then are unavailable for research. They say science is hampered by granting private ownership rights for ancient remains.

In 2016, a judge ruled that the fossil did not qualify as a mineral resource. U.S. District Judge Susan Watters of Billings said it wasn’t the composition of minerals that had value. Gold, for instance, is always valuable whether it is in the ground or shaped into coins or jewelry. But the fossil was valuable not for its makeup but for other characteristics: the species of dinosaurs represented, the circumstances at the time the creatures died, the preservation of the historical event.

The Seversons weren’t happy with Judge Watters’ decision. They appealed. A second court sided with them in a split decision in early November. Two of three judges on the 9th U.S. Circuit Court of Appeals ruled that the Dueling Dinosaurs are minerals, both scientifically and under mineral rights laws. If that decision holds, the brothers will be entitled to two-thirds of all proceeds from the sale of any fossils found on the site.

A nearly complete Tyrannosaurus rex fossil unearthed there sold for several million dollars in 2014. The funds have been held in a bank ever since—waiting for a final court decision about who the money goes to. Attorneys for the Murrays say they plan to ask for yet another hearing.