Remains of dozens of sea dinosaurs are found
By Tony Paterson in Berlin
(Filed: 09/05/2004)
The world's biggest and best-preserved collection of marine dinosaur bones, offering scientists vital clues about how prehistoric animals swam and moved, has been excavated from a site in southern Germany.
The pristine remains of dozens of prehistoric dolphin and whale-like reptiles, known as ichthyosauruses and weighing up to 30 tons, are more than 180 million years old.
Until now, most ichthyosaurus remains that have been discovered have been fossils, crushed under the weight of many thousands of years of glacier and earth movements.
By contrast, these remains are almost three-dimensional, preserved in a comparatively soft mixture of clay and chalk.
"The sheer number of skeletons and above all their condition make the find unique," said Reinhard Rademacher, one of the palaeontologists who has begun excavating the site, near Eislingen in Baden-Wurttemberg.
"Nothing like it has ever been seen before."
Michael Maisch, an expert on prehistoric fish at Tubingen university, said: "We still don't know how these giant fish actually swam. But because the skeletons are three-dimensional, we will be able to find out. The quality of the skeletons is fantastic."
The giant animals once roamed an ocean above what is now southern Germany. Scientists believe that they moved at speeds of up to 25 knots and fed mainly on prehistoric cuttlefish known as belemnites.
German palaeontologists believe that they were killed by a big bubble of methane gas that erupted from the seabed.
Archaeologists from Tubingen university were drawn to the site in June 2002 after students stumbled across fragments of a large fish skull that had been unearthed by bulldozers.
The archaeologists and palaeontologists were astounded by the scale of the site. To date, they have unearthed nine complete ichthyosaurus skeletons and located the remains of a further 17. They are certain that many more skeletons lie beneath what they have already found.
Baffled as to why so many ichthyosauruses died together, they initially assumed that they had become trapped beneath submerged tree trunks and were unable to reach the surface and find air.
After examining rock particles with an electron microscope, however, they reached a different conclusion: "We are almost certain that the planet Earth literally burped and killed them," said Michael Montenari, a geology expert at Tubingen, who carried out the tests.
He said that the rock particles should have contained carbon, but didn't - suggesting that large amounts of poisonous methane gas and sulphur oxide were present in the water.
He believes that the methane, produced by submerged rotting vegetation, erupted from the seabed and poisoned them en masse.
"Once dead, they would have sunk to the seabed where they appear to have been piled up in a trench by a current. We appear to have discovered the trench some 181 million years later."
SOURCE:
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