How the discovery of Eva the dinosaur has altered history

From a distance, Eva looks like a heap of stones projecting from the blood-red soil and rock of the Aude, in south-west France. As you approach and peer, however, the outline of her vertebrae, ribs, femur and part of her tail emerge, like pale shreds in a gigantic jar of rich marmalade.

Eva – named after the student who found her – has been trapped in the sandstone of the Pyrenean foothills for 72 million years. Her jaw has already been removed for safe-keeping. She is the best preserved, large dinosaur skeleton to be found in France, and the most complete to be found in Europe for more than 20 years.

Even though she probably died young, she was, in life, 12 metres long and almost three metres tall. She had a sinuous neck and tail, and large protective plates on her back. ("She" is a courtesy title: it is extremely difficult to sex the remains of dinosaurs.)

Eva belongs to a new species of herbivorous dinosaur – the ampelosaurus or "vineyard dinosaur", part of the sauropod family. The species was first identified seven years ago, after a less complete skeleton was found on the same site, high above the valley of the river Aude, 30 miles south of Carcassonne.

The local – bubbly – white wine, Blanquette de Limoux, which claims to pre-date champagne by a couple of centuries was once grown on the bright red hillside. But in the past 13 years, the vineyard has become a palaeontological treasure trove, yielding more than 2,000 fossilised remains of prehistoric creatures, including several other types of dinosaur, crocodiles, turtles and a previously unknown, giant flightless bird, almost as large as an ostrich.

Eva is the most spectacular find to date. No complete, or near-complete, dinosaur skeleton this large has been found in France before, even though France, after Britain, was one of the first countries where dinosaur remains were identified in the early 19th century.

All the fossils found on the slope above Campagne-sur-Aude come from the last 10 million years of the 150-million-year reign of the giant lizards. Jean Le Loeuff, 37, the director of digging on the site and curator of the excellent dinosaur museum created in the neighbouring town of Espéraza, says that the "lateness" of the site makes it especially significant.

"The fascination of dinosaurs is partly one of pure exploration of the unknown, of pure science," he said. "But dinosaurs also hold the key to a mystery – why did they disappear, after dominating the earth for so long? This is potentially of inestimable value for the survival of present-day species, including our own."

The latest theories, developed in the United States, suggest that dinosaurs gradually disappeared over many millions of years and that their numbers, and the variety of their species, were much reduced towards the end.

Exploration of the site in the Aude suggests the opposite, says Mr Le Loeuff. "Our finds from the very end of the dinosaur period, some time after Eva, around 65 million years ago, suggest that there was the same, wide range of species as 10 million years before or earlier. In other words, we may have to go back to the earlier thesis that there was a kind of big bang, a cataclysmic event, perhaps a large meteor strike, which wiped out all the dinosaurs in a very short period of time."

Eva is already well on the way to becoming a star. Visits to the dinosaur museum in Espéraza, including a guided trip to the dinosaur dig three kilometres away, have trebled since her discovery was announced last week.

In fact, part of Eva was unearthed last year, by a young student from Brittany, at the end of the summer digging season. Mr Le Loeuff and his team, though excited by the likely scale of their find, covered her up again. They waited for a longer period of good weather in which to separate her remains painstakingly from the rock in which they have been embedded for 720,000 centuries.

The digging so far this summer has confirmed what Mr Le Loeuff had hoped. Eva is a complete, or near complete skeleton, from her jaw to her tail. Mechanical diggers – which look curiously like dinosaurs – are being used to remove seven metres of rock and earth from the slope above Eva's resting place. Once that work is completed, Mr Le Loeuff hopes to be able to remove most of Eva's remains in one large, block of rock which will be taken back to the workshop and museum at Espéraza for careful separation.

Eventually, it is hoped, it may be possible to display Eva as a complete, mounted skeleton. In the meantime, the impressive "model" of a full-size ampelosaurus on show in the museum will have to be revised and reconstructed. The discovery of Eva has forced Mr Le Loeuff and his team to reconsider their views of what an ampelosaurus looked like: previous finds had not revealed the large protective plates on the creature's back.

In the meantime, exploration of the site at Campagne-sur-Aude is yielding other treasures, including another ampelosaurus skeleton, probably less complete than Eva's. When these creatures were alive 72 million years ago, the Pyrenees had not yet been created and the Aude was part of a giant plain. Eva and the other fossils were preserved in what had been the sediment of a giant river bed.

Some people have found the discovery of such a complete skeleton 170 years after the first dinosaur finds in France surprising, but Mr Le Loeuff has not. "It's almost predictable," he says. "The fact is nobody much has been looking for them. Until recently, dinosaurs have been a low priority for palaeontologists in France and palaeontology itself – in the whole world, not just in France – has been neglected compared to other sciences."

Mr Le Loeuff believes that many other Evas may be buried beneath the French countryside. He hopes that the dinosaur obsession of modern children – what he calls the "Jurassic Park generation" – will survive as they grow older and generate a renewed interest in hunting dinosaurs.

Rise and fall of the giant lizards

Both the rise and fall of the dinosaurs (whose name means giant lizards) is believed to have been caused by asteroids hitting Earth. The first, 200 million years ago, precipitated the climatic and environmental changes that helped dinosaurs thrive – the second, 65 million years ago, triggered changes that led to their extinction and the rise of mammals.

While many people are familiar with the idea of the second event – which has been immortalised in film – the first has only been discovered more recently.

In May this year, scientists announced the results of studies at more than 70 locations in eastern North America. They had been investigating the makeup of the "Triassic-Jurassic boundary" – a geological boundary between two periods in the planet's history.

The Triassic era is best known for the trilobites while the Jurassic is famous for the rise of the dinosaurs.

But what has always been puzzling is why there was apparently a huge decrease in the number of species at the end of the Triassic, despite no radical changes in the Earth's geology. What Dennis Kent, a geology professor at Rutgers University, found was iridium dust, and disturbed magnetic fields, in the sediment layers . Iridium is essentially a marker of a comet or asteroid impact, noted Professor Kent. He reckons the asteroid impact killed off many competing species, allowing the dinosaurs to flourish.

That continued for 135 million years; then another asteroid, reckoned to be between 100 and 160km wide smacked into the Yucatan Peninsula off Mexico. The shock waves generated could have thrown up methane that would ignite and cause firestorms around the world; then the dust thrown up by the impact would have cooled the Earth for decades, causing another mass extinction in which only those animals able to maintain their body heat to survive. (Some dinosaurs may have been able to do that; mammals certainly could.)

Charles Arthur