Thick tooth discovery uncovers secrets of giant ichthyosaurs marine mammals

A tooth twice as large as the biggest aquatic dinosaur tooth to date has been found by researchers in the Alps of Switzerland.

The discovery has helped uncover secrets about a type of giant marine reptile - the ichthyosaurs - which was previously unknown.

The first ichthyosaurs were swimming in oceans around 250 million years ago and with an estimated weight of 80 tonnes and a length of more than 20 metres, these prehistoric giants would have rivalled a sperm whale.

After the marine mammals became extinct 200 million years ago, and the earth's tectonic plates shifted to form the Alps, the fossils of these giants ended up hidden in glaciers at an altitude of 2,800 metres.

Now the discovery of more remains has excited researchers. From one of the ichthyosaurs, a vertebra was found preserved together with ten rib fragments, but it was a big tooth that got the most attention.

"From our point of view the tooth is particularly exciting," explains Prof Dr Martin Sander from the Section Paleontology at the Institute of Geosciences at the University of Bonn.

"Because this is huge by ichthyosaur standards. Its root was 60 millimetres in diameter - the largest specimen still in a complete skull to date was 20 millimetres and came from an ichthyosaur that was nearly 18 metres long."

His colleague Heinz Furrer reiterated the scale of the find: "Our finds belonged to the world's longest ichthyosaur; with the thickest tooth found to date and the largest trunk vertebra in Europe!"

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But the find may not show the big marine mammals were all that much bigger than previously thought.

"The tooth diameter cannot be used to directly infer the length of its owner," said palaeontologist Prof Dr Sander.

That's because research suggests extreme gigantism and a predatory lifestyle (which requires teeth) are incompatible. It is, therefore, possible that the tooth did not come from a particularly gigantic ichthyosaur - but from an ichthyosaur with particularly gigantic teeth.