FORT WORTH, Texas — A doctor in Texas with a passion for paleontology is challenging the federal government after authorities seized a 70 million-year-old dinosaur skull from his fossil collection.

Dr. James Godwin argues that the government waited too long to file a forfeiture claim after it seized the Tyrannosaurus bataar skull that authorities say was among several fossils smuggled illegally out of Mongolia. Under the National Stolen Property Act, the government has five years from the time an offense is discovered to file a forfeiture lawsuit.

Federal investigators said the skull was unearthed from the Gobi Desert between 2000 and 2011 and it traded hands several times before it ended up at a store in Wyoming, where Godwin acquired it. Agents seized the fossil from Godwin in July 2013 and a forfeiture claim was filed in August 2017.

But Godwin’s attorney argued that the government surpassed the five-year window to file a claim because, he said, agents first became aware of Godwin’s connection to the fossil in July 2012.

“The statute of limitations begins when the government possesses facts sufficient to trigger an investigation — not whenever the government decides it has sufficiently verified the facts,” attorney Michael A. Villa Jr. said in a recent court filing.

According to the Dallas Morning News , a judge in Fort Worth heard testimony Tuesday in the case and says he’ll rule at a later date. The fossil is now being stored at the Museum of the Rockies in Bozeman, Montana.