European palaeontologists are benefiting from the illegal side of the international fossil trade.
Rare specimens of extinct life, such as Brazilian Pterosaurs and Chinese dinosaur eggs, are being smuggled into Europe, despite national laws that forbid their export without express permission.
Although most European museums and universities have codes of practice to protect against illegal purchases, it is accepted that the necessary paperwork can be acquired by dealers through bribery.
A THES investigation has found that many rare, scientifically important specimens are unearthed as a by-product of the large-scale illicit excavation of more common fossils to meet commercial demand.
Palaeontological collections across the United Kingdom contain a large amount of material bought from dealers with whom many museums have developed good working relationships.
Most have been able to make only small purchases in recent years, relying on donations and having to mount their own expeditions to provide fossils for research, education and displays.
Paul Ensom, head of curation in the Natural History Museum's department of palaeontology, said: "While we have received Brazilian fossils, both fish and reptile material, we always follow back all the paperwork to make sure it is in order."
However, he admitted that some of the better specimens were probably a "spin-off" product of a commercial trade that had a lucrative illegal side. There is also a fear that important specimens could be lost to science if they are allowed to go to private collectors.
Philip Doughty, former keeper of geology at the National Museums and Galleries of Northern Ireland, said his institution had bought dinosaur remains from Kazakhstan a few years ago that possessed full documentation but still left some experts concerned about their origins.
"We had some suspicions, but if we bought the material, at least it would be in a public collection," he said. The fossils turned out to be above board.
David Unwin, curator for fossil reptiles and birds at the Museum fur Naturkunde at the Humboldt University in Berlin, Germany, said: "Curators purchasing fossil material always do their best to establish the provenance of specimens and any questions regarding the legality of material, but with limited time and resources there is a serious restriction on what we can do."
The provenance of fossils will not be considered by the House of Commons select committee that has just begun examining archaeological and artistic museum collections. But Labour MP Tam Dalyell is considering putting together a private member's bill to introduce legislation.
"Fossils are part of the world's heritage. I would try to bring in legislation imposing penalties on illegal importation," he said.
However, there is a growing number of UK palaeontologists who want to see legal restrictions on the trade lifted.
They would prefer the trade be licensed so that scientifically significant material could be legally acquired by the scientific community.
Many fear that repressive legislation will not end the trade but drive it further into the shadows, resulting in more specimens winding up in private collections and being lost to science.
John Martin, managing curator of the Leicester Museum and Art Gallery, said it was better that the scientific community bought important specimens than they were lost, even if that meant dealing with a trade that had a dubious aspect to it.
"We should get rid of restrictive legislation and make it much easier for these objects to get into the public domain," he said.
David Martill, a palaeontologist from Portsmouth University, who has studied the Brazilian fossil beds extensively, said a licensing scheme would result in more money going to local people rather than middlemen, provide facilities for local scientists and make good fossils available internationally.
It is an approach rejected by Alexander Kellner, chairman of the department of geology and palaeontology at the Museu Nacional in Rio de Janeiro, who argues this would allow rich scientists from Europe, North America and Asia to outbid the Brazilian scientists for the best samples.
"Scientists around the world should be aware that despite the problems associated with this illegal trade, there is a Brazilian palaeontological community that is doing research on these fossils," he said.
He said it was possible that, in the future, the Brazilian government would demand the return of all fossils that had been acquired illegally.
In Brazil, most of these were illegally dug up by peasants, secretly transported across the country and then either sold to tourists or smuggled to sell on to private collectors abroad.
A large shipment of fossils was intercepted by the authorities in Sio Paulo two weeks ago, but generally officials have been unable to stop the trade.