On the morning of October 17, 2012, a cadre of federal agents and sheriff’s deputies in Gainesville, Florida, went to the home of a suspected fossil smuggler named Eric Prokopi and arrested him.

As I reported in The New Yorker in January, 2013, the case against Prokopi was unusual and aggressive: it included several counts of felonious smuggling, and characterizations of the defendant as a “one-man black market.” Two months after his arrest, Prokopi pleaded guilty to smuggling the bones of a Tarbosaurus bataar, a Tyrannosaurus rex cousin that lived seventy million years ago in the Gobi Desert of Mongolia, which prohibits the commercialization of natural history.

Facing a possible seventeen years in prison, Prokopi started talking. In the seventeen months since he pleaded guilty, he has helped to widen the U.S. investigation into fossil smuggling, providing details about specific specimens, dates, and locations. “There is probably not an active fossil investigation at this point that doesn’t owe, on some level, to information that Mr. Prokopi has furnished law enforcement,” Martin Bell, an assistant U.S. Attorney, told the U.S. District Judge Alvin Hellerstein last week, when Prokopi returned to the federal courthouse in lower Manhattan for sentencing. The case has pushed federal authorities to get their “act together” with respect to “the policing of this admittedly obscure area,” Bell said, adding, “The government’s only recently realizing the contours of that black market, and what it is.”

Prokopi’s cooperation with authorities has led to the recovery and repatriation of not only the T. bataar but also other Mongolian fossils—enough to populate a new dinosaur museum in Ulaanbaatar. In court on Tuesday, Bell reported that “over eighteen largely complete, if not fully prepped, dinosaur fossils will be returned as a result, indirectly or directly, of Mr. Prokopi’s information, to Mongolia, a country which is not only enthusiastic about the possibility of dinosaur tourism based solely on the haul from this case but which badly seems to need it.” The returned specimens included “a second Tyrannosaurus skeleton; a dinosaur called an oviraptor, which is an egg-eating thing,” Bell said. “I think a number of them stampeded in the 1996 movie ‘Jurassic Park.’ It might have been 1992. I was young and awestruck in any event, Your Honor.”

“I missed the movie,” the judge said. “Maybe I should go back to see it.”

“Every now and then it airs on TNT.”

Fossil poaching is neither new nor especially rare, and mostly happens in fossil-rich countries such as China, Argentina, and the United States. A fossil that is removed and sold into private hands, without correlating data, loses its scientific importance, and so paleontologists are bitterly opposed to even the legal trade in fossils. Prokopi and his like-minded colleagues—“commercial paleontologists”—argue that, if not for them, fossils would turn to ash. It’s an old feud, unresolved.

Fossil-poaching and smuggling cases usually end in plea bargains. A Prokopi trial might have revealed more than has ever been publicly known about how the international market works: the siting of digs, the excavation methods, the middlemen, the shipping routes, the buyers, the motivations, the money. “It was never just about the money,” Prokopi’s attorney, Georges Lederman, told the court last week. “He never had any expensive boats, expensive cars, expensive planes, jewelry, jewels, watches, never took expensive trips. The little money he did make”—Prokopi would have netted about three hundred and fifty thousand dollars from the T. bataar sale—“he then would reinvest into subsequent fossil projects because of the love of his craft.”

Prokopi grew up hunting shark teeth and other fossils on the shores and in the rivers of central Florida. Now forty, he’s tall, with the broad-shouldered build of a swimmer, and he doesn’t talk a lot. He easily might have put his University of Florida engineering degree to better use—and he did, to the extent that he used his education to renovate and flip houses—but what really captivated him was hunting prehistoric animal treasure. He got interested in Mongolian dinosaurs through the huge fossil-and-mineral show that takes over Tucson each February, attracting many thousands of dealers, buyers, and browsers from around the world. Illicit materials often turn up at the Tucson show and at a smaller one in Denver; the events are rarely policed. A novice could get the impression that selling fossils from Argentina or China or Mongolia is legal, when it isn’t.

Working with a Mongolian guide whom Prokopi trusted (and who has since died), Prokopi moved fossils that had been extracted from the Nemegt Formation, a fruitful expanse of Late Cretaceous sandstone and mudstone. He believed that he had permission to do so; once the bones reached a business associate in Great Britain, Prokopi realized that he was dealing with contraband—yet, according to last week’s hearing, imported it to the U.S. anyway, largely describing it on customs forms as “reptiles.”

The dinosaur arrived in Florida via U.P.S. Prokopi uncrated the nearly three thousand pounds of bones in his back-yard workshop, behind his saltwater swimming pool. Using techniques that he had learned from half a lifetime of hunting and prepping fossils, he cleaned and restored the remains, and reassembled a creature—eight feet tall, twenty-four feet long. Many months later, he sold the specimen at auction, in New York, to an anonymous bidder, for just over a million dollars. The buyer was Coleman Burke, a Manhattan real-estate developer, lawyer, and adventurer who wanted the T. bataar as a showpiece for his office building, on the West Side Highway. (Burke, who is in his seventies, had hunted fossils in Argentina.)

The sale did not go through. The government of Mongolia heard about the auction and, through Robert Painter, a Houston lawyer, sued for the recovery of the T. bataar. Prokopi tried to save his investment by brokering a quiet deal with the Mongolians. Just four days after the sale, in an e-mail exchange with the company that had handled the auction, Prokopi wrote, “If the Mongolian president is indeed only interested in getting to the bottom of the [fossil] sources, and wants to look good for his people, I think I can help him do that if he is willing to cooperate and compromise. If he only wants to take the skeleton and try to put an end to the black market, he will have a fight and will only drive the black market deeper underground.” Prokopi advised that he knew “just about all of the people involved in the business of central asian fossils, and could offer ideas and help to make permanent changes that would nearly eliminate the black market.”

The offer became leverage after Prokopi’s legal troubles grew from a civil action to a criminal one. His “substantial assistance” generated greater knowledge about the black market in fossils, a market that Bell said “was sufficiently ignored for a time” and “able to hide in plain sight.” The T. bataar case is “part of what you might call … a law-enforcement renaissance when it comes to this particular field of dealing in stolen fossils,” the prosecutor said. Investigations are now pending in Wyoming, California, and New York, based on information that Prokopi gave the federal government.

In April, a fossil dealer who sold pieces through By Nature Gallery shops in Jackson Hole, Wyoming, and Avon, Colorado, pleaded guilty to conspiring to smuggle fossils from China. The plea agreement called for Rick Rolater, who is sixty-nine, to surrender fossils that included a Tyrannosaurus skull from Mongolia. Prosecutors described some shipments as intentionally mislabelled to pass inspection. A federal judge ordered Rolater to serve two years of supervised probation and to pay a twenty-five-thousand-dollar fine, but expressed skepticism that the punishment would have an impact. “He knew better, but he liked the money,” Judge Scott Skavdahl reportedly said in court.