Eight years ago, the skull of a Tyrannosaurus bataar was the star artifact in a natural history-themed luxury auction in Manhattan. It sold for $276,000 to an anonymous buyer.

As it turns out, the skull had been stolen from the Gobi Desert in Mongolia, and the buyer was Nicolas Cage, an actor who among his dozens of films has starred in a movie franchise about the hunt for rare treasures.

A publicist for Mr. Cage confirmed that he bought the skull from the Beverly Hills gallery I.M. Chait in 2007, according to Reuters. The Department of Homeland Security contacted Mr. Cage about the skull last year, and the actor agreed to turn it over.

Since 2012, the office of Preet Bharara, the United States attorney in Manhattan, has worked to return artifacts taken from Mongolia. Many stolen remains have been traced to a Florida man named Eric Prokopi, who in 2012 was arrested and charged with smuggling illegal goods and possessing stolen property. Last year, Mr. Prokopi was sentenced to three months in prison.