Pricing is much easier for museums and public institutions to compete with rich collectors. And when these samples are put into private hands, they are more or less lost in science, experts say.
"Selling fossils destroys information because it is unethical to examine samples that are not in public trust," Carr said, because privately owned fossils exclude independent analysis and verification of findings.
This sale is particularly worrying, said Carr, due to the lack of juvenile fossils T. rex left paleontologists with gaps in their understanding of dinosaur life. He casts commercial fossil hunters as a "time thief".
"Absolutely every other fossil is crucial to getting a picture of how young T. rex was," Carr said.
Detrich, a 71-year-old who is not a paleontologist, discovered T. Rexe on private land he rented in Jordan in Montana in 2013. Most fossil-rich counties, such as China and Mongolia, have strict rights surrounding the collection and sale of fossils. Cage had to give up the Tyrannosaurus bataar skull, which DiCaprio overcame in 2007 because he could have been illegally smuggled from Mongolia.
After the experts helped Detrich understand what he had – the four-year-old T. rex – he decided to lend it to the Natural History Museum at the University of Kansas near his Lawrence house in 2017. She thought the public should see it.
But last week, without university warning, T. rex said on eBay. His first contribution emphasized the prominent depiction of fossil materials at school as a key selling point.
The museum quickly clarified that it was not participating in the sale and that the fossil was removed and returned to Detrich. In a statement, the director of the museum, Leonard Krishtalka, said that Detrich was asked to remove links to the university from the list.
The move has also drawn criticism from the wider academic and scientific communities. The vertebrate paleontology company has written an open letter condemning the sale of T. rex, stressing that the price tag would probably ensure that the specimen ends up being a private owner, robbing scientists and the public of learning from it.
"That fossils like this are proof of Earth's deep past is what makes them valuable, unlike art objects or other objects of commerce whose value comes from human creativity and art," the letter said. "Anyone who is lost from public confidence is part of that fragmentary history that we will never collectively recover."
But many professional fossil retailers reject the idea that samples in private hands are lost for science. Michael Triebold, who has been commercially collecting fossils for more than 30 years, said museums often depend on companies such as his exhibits. He also refuted the idea that samples should be kept in public confidence.
"Samples are borrowed and never returned, samples are stolen, lost by various means, including laziness and incompetence," Triebold said. "I dare to suggest that a private fossil of any scientific significance is provided for better than public confidence."
Detrich bristles on the suggestion that he is only interested in money and has no respect for history. Without him, the skeleton would still be buried under dirt, hidden and anonymous. He said scientists and the public had access to T. rex in the past two years. He claims he deserves to be compensated.
Detrich has not yet received an offer, but says he is heard from perspectives around the world and that some people have even asked about shipping costs. The list is an average of 116 impressions per hour on eBay.
For a man whose products are millions of years old, Detrich's views are based on transience: "Billionaires will die just like the rest of us. Once it ends in the museum. What matters if it's not another 20 years? "