Jurassic Coast: Incredible Ichthyosaur jaw discovered on the beach
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The specimens were found preserved in the so-called Kössen Formation, a layer of carbonate-rich rocks deposited in a shallow lagoon more than 200 million years ago. As the African and Eurasian tectonic plates slowly collided, however, the rock was thrust upwards during the mountain-building event that created the Alps we see today. It was during geological mapping of the rocks in the Swiss canton of the Grisons between 1976–1990 that palaeontologist Dr Heinz Furrer of the University of Zurich and his students collected the fossils — only for them to spend a couple of decades largely forgotten.
Dr Furrer said: “Recently, though, more remains of giant ichthyosaurs have appeared.
“So it seemed worthwhile to us to analyse the Swiss finds again in more detail as well.”
The team report that the long-overlooked haul, believed to represent three individuals, includes the remains of the largest trunk vertebrae ever found in Europe — bones belonging to an ichthyosaur that would, in size, likely have rivalled the largest known marine reptiles.
At present, the record for the world’s biggest marine reptile goes to Shastasaurus sikkanniensis, another ichthyosaur, that lived around 210 million years ago in what is today British Columbia, in Canada, and grew to a whopping 69 feet long.
The team also recovered the largest ichthyosaur tooth ever found, one whose root width was twice as large as those from any aquatic reptile previously known to science.
Not all ichthyosaurs had teeth — most are thought to have fed by sucking in their squid-like cephalopod prey — but those who did are believed to have likely eaten smaller ichthyosaurs and large fish.
Paper co-author and palaeontologist Professor Martin Sander of the University of Bonn said that, from their point of view, “the tooth is particularly exciting”.
He added: “Because this is huge by ichthyosaur standards. Its root was 60 millimetres [2.4 inches] in diameter.
“The largest specimen still in a complete skull to date was 20 millimetres [0.8 inches] and came from an ichthyosaur that was nearly 18 metres [59 feet] long.
“It is hard to say if the tooth is from a large ichthyosaur with giant teeth or from a giant ichthyosaur with average-sized teeth.”
The team have not been able to assign the tooth to a particular species, as the specimen was broken off at the crown, but the distinctive infolding in the dentin of the root enabled them to be sure it did come from an ichthyosaur.
This feature is only seen in one other group: that of monitor lizards.
Able to grow to a whopping 80 tonnes, ichthyosaurs would have ordinarily patrolled the waters of “Panthalassa”, the world ocean which surrounded the supercontinent Pangea during the Late Triassic, some 205 million years ago.
However, these discoveries of their remains in a carbonate lagoon reveal that they would also have made forays in the shallow seas of the Tethys Ocean — which would eventually cleave Pangea in two — on the eastern side of the supercontinent.
First emerging in the wake of the devastating Permian mass extinction around 252 million years ago, ichthyosaurs reached their greatest diversity in the Middle Triassic, although some persisted into the Late Cretaceous, some 90 million years ago, before the order finally went extinct.
Fossils of the roughly whale-shaped creatures have mainly been found in Europe and North America, although specimens have been unearthed in South America, Asia and Australia.
Until now, the larger specimens were mainly found in North America — and thus the discovery of new behemoths in Switzerland expands their known range.
Prof Sander said: “It amounts to a major embarrassment for palaeontology that we know so little about these giant ichthyosaurs despite the extraordinary size of their fossils.
“We hope to rise to this challenge and find new and better fossils soon”
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Prof. Sander added that the team is hopeful more remains from the giant sea creatures might be found hidden beneath the glaciers of the Swiss Alps.
He said: “Bigger is always better. There are distinct selective advantages to large body size. Life will go there if it can.
“There were only three animal groups that had masses greater than 10–20 metric tonnes: long-necked dinosaurs (sauropods), whales, and the giant ichthyosaurs of the Triassic.”
The full findings of the study were published in the Journal of Vertebrate Paleontology.
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