ENGLAND - Armed with rock chisels, it took the thief only a few minutes to wipe out 135 million years of history. The fossilised iguanodon footprint was hacked out of the limestone slab where it had lain in a Dorset quarry and spirited away by an illicit collector.

Some 8000km away in southern India, scientists last month issued a plea for villagers and even student palaeontologists to halt the mass looting of hundreds of dinosaur eggs whose petrified embryos could shed new light on the extinction of a species.

Fascination with the ferocious beasts has never been greater, with scientists announcing almost weekly the discovery of new prehistoric species from giant crocodiles to feathered lizards that bear testimony to an evolutionary link with birds.

But with a pristine Tyrannosaurus rex specimen fetching up to US$8.3m (NZ$11.4m), there is growing concern that a booming trade in stolen or illicit fossils is wrecking unique sites and seeing previously unknown species disappear into private collections, where they are lost to science.

One of the world's leading palaeontologists told The Independent that fossil rustling had become a "huge international problem" stretching from developed markets like Britain to dinosaur hotspots such as Mongolia and China.

The speed and anonymity of the internet has led to a thriving black market linking unscrupulous dealers to private collectors interested in "trophy" fossils for display rather than study.

Once a fossil is dug out of the ground without proper recording of information such as its location and depth, at least half its scientific value is lost.

Even a correctly-recorded specimen which ends up in private hands is lost to science because scientific journals do not publish research on specimens which cannot be readily accessed or peer reviewed.

Professor Philip Currie of the University of Alberta, an eminent Canadian scientist who is chairman of the ethics committee of the Society of Vertebrate Palaeontology, said: "This is a huge international problem that affects most of us who do research in the field. I do a lot of work in China and Mongolia, where highly significant fossils, including new species of animals, feathered dinosaurs and birds, are regularly smuggled out illegally and sold at big international fossil shows and over the web.

"I have seen many quarries [in Mongolia] where, in the quest for illicit profit, specimens have been destroyed by incompetent collectors looking for teeth and claws. The destruction of specimens that survived underground for 75 million years only to be ripped up for a few dollars is heart-rending."

After a spate of thefts in Scotland and northern England seven years ago, when fossil hunters armed with diggers, electric saws and dynamite stole stones worth ten of thousands of pounds, police and wildlife conservation bodies launched a campaign to crack down on illegal collectors.