FORT WORTH (AP) — 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.