New York federal prosecutors are seeking to return a Tyrannosaurus bataar skull to Mongolia after an anonymous buyer purchased it at auction in the United States in 2007 for $276,000.

Prosecutors filed papers in Manhattan federal court Tuesday to formally secure the 32-inch-long skull. Federal authorities say the California buyer who purchased it already agreed to give it up.

Manhattan prosecutors say the 67 million-year-old skull will be among more than a dozen dinosaur skeletons that have been returned to Mongolia since 2012. They say other items returned to Mongolia include a nest of dinosaur eggs and the relics of numerous small and unidentified lizards and turtles.

Prosecutors say the skull was unlawfully taken from the Gobi Desert in Mongolia and was smuggled into the United States in June 2006.