Illustration: - 200 million year old deposits of the precursor of the Mediterranean Sea have been preserved in the Swiss High Alps. Whale-sized ichthyosaurs came from the open sea only occasionally into shallower water.

One of the largest animals ever discovered in the Alps

The rebuilding of marine ecosystems after the devastation at the end of the Permian invited several lines of reptiles to the marine habitat, leading to the well-known explosive radiation of marine reptiles in the early Triassic and early Middle Triassic.

Two major lines of marine reptiles, the ichthyosaurs and the sauropterygies, were part of this explosive radiation.

As reported in a new article in the peer-reviewed Journal of Vertebrate PaleontologyPaleontologists have discovered sets of fossils representing three new ichthyosaurs that may have been among the largest animals that have ever lived.

The discovery was excavated in the Swiss Alps between 1976 and 1990 and includes the largest ichthyosaur tooth ever found. The width of the tooth root is twice as large as any known aquatic reptile, the former largest belonging to a 15 meter long ichthyosaur.

Other incomplete skeletal remains include the largest vertebral vertebra in Europe, showing another ichthyosaur competing with the largest marine reptile fossil known today, the 21-meter-long Shastasaurus sikkanniensis from British Columbia, Canada.

Dr Heinz Furrer, co-author of this study, was part of a team that found the fossils during geological mapping in the Kössen Formation in the Alps. The rock layers covered the seabed more than 200 million years earlier. But with the folding of the Alps, they had reached an altitude of 2,800 meters!

Now retired curator at University of Zurich‘s Paleontological Institute and Museum, said Dr. Furrer that he was happy to have discovered “the world’s longest ichthyosaur; with the thickest tooth ever found and the largest torso vertebra in Europe!”

Lead author P. Martin Sandler by University of Bonn hope “there may be more remains of the giant sea creatures hidden under the glaciers.”

“Bigger is always better,” he says. “There are clear selective advantages to large body size. Life will go there if it can. There were only three groups of animals that had a mass larger than 10-20 metric tons: long-necked dinosaurs (sauropods); whales; and the giant ichthyosaurs from the Triassic. . “

Ichthyosaurs colonized the open sea early, which explains their presence throughout the northern hemisphere. Ichthyosaurs also increased in body size incredibly rapidly, having developed giant forms with a skull length of 2 m within 5 Ma after their first appearance in the early Middle Triassic. Throughout the Triassic, ichthyosaurs seem to dominate the world’s oceans and show great diversity and diversity.

These monstrous 80-tonne reptiles patrolled Panthalassa, the world’s oceans surrounding the supercontinent Pangea during the Late Triassic, about 205 million years ago. They also raided Tethy’s shallow seas on the eastern side of Pangea, as evidenced by the new finds.

Ichthyosaurs first appeared in the wake of the Permian extinction about 250 million years ago, when about 95 percent of marine species became extinct. The group reached its greatest diversity in the Middle Triassic, and a few species continued into the Cretaceous. Most were much smaller than S. sikanniensis and the species of similar size described in the magazine.

Roughly in the form of contemporary whales, ichthyosaurs had elongated bodies and upright tail fins. Fossils are concentrated in North America and Europe, but ichthyosaurs have also been found in South America, Asia and Australia. Giant species have mostly been excavated in North America, with few finds from the Himalayas and New Caledonia, so the discovery of additional giants in Switzerland represents an expansion of their known range.

But so little is known about these giants that there are only ghosts. Exciting evidence from Britain, consisting of a huge toothless jawbone, and from New Zealand suggests that some of them were as big as blue whales. A newspaper from 1878 credibly describes the ichthyosaur vertebra 45 cm in diameter from there, but the fossil never came to London and may have been lost at sea. Sander notes that “it is a great embarrassment to paleontology that we know so little about these giant ichthyosaurs despite the extraordinary size of their fossils. We hope to take on this challenge and soon find new and better fossils. ”

These new specimens probably represent the last of the Levites. “In Nevada, we see the beginning of true giants, and in the Alps, the end,” says Sander, who also co-authored an article last year about an early giant ichthyosaur from Nevada’s Fossil Hill. “Only the medium to large dolphins – and killer whale-like shapes survived into the Jurassic.”

Giant tooth fragment

“Many of the giant ichthyosaurs from sentrias appear to have no teeth. The only safe exception is the Himalayasaurus (Motani et al., 1999) and the tooth PIMUZ A / III 670 described in this study.” The study mentions.

The root of the tooth - found has a diameter of 60 Millimeters.  This makes it the thickest ichthyosaur tooth found so far.
The root of the tooth – found has a diameter of 60 millimeters. This makes it the thickest ichthyosaur tooth found so far. Credit: © Rosi Roth / University of Zurich

While the smaller ichthyosaurs usually had teeth, most of the known giant species appear to have been toothless. One hypothesis suggests that they are fed by suction rather than seizing their prey. – The bulk feeders among the giants must have fed on octopuses. Those with teeth probably feed on smaller ichthyosaurs and large fish, says Sander.

The tooth described by the magazine is just the second example of a giant ichthyosaur with teeth – the other is the 15 meter long Himalayasaurus. These species probably had similar ecological roles as modern sperm whales and killer whales. The teeth are actually bent inwards like those of their mammalian successors, indicating a feeding approach that helps to catch prey like giant octopuses.

“It is difficult to say whether the tooth is from a large ichthyosaur with giant teeth or from a giant ichthyosaur with medium-sized teeth,” Sander admits crookedly. Because the tooth described in the newspaper was broken off at the crown, the authors could not with certainty assign it to a certain taxon. Nevertheless, a peculiarity of dental anatomy allowed researchers to identify it as belonging to an ichthyosaur.

“Ichthyosaurs have a property in their teeth that is almost unique among reptiles: the entanglement of the dentin in the roots of their teeth,” explains Sander. “The only other group that shows this is lizards.”

Largest vertebra

The two sets of skeletal remains, consisting of vertebrae, ten rib fragments and seven associated vertebrae, have been assigned to the family Shastasauridae, which contains the giants Shastasaurus, Shonisaurus and Himalayasaurus. Comparing the vertebrae from a set suggests that they may have been as large or slightly smaller than those of S. sikkanniensis. These measurements are somewhat skewed by the fact that the fossils have been tectonically deformed – that is, they have literally been squeezed together by the movements of the tectonic plates whose collision led them to move from a previous seabed to the top of a mountain.

Heinz Furrer - with the largest ichthyosaur vertebrae.
Heinz Furrer – with the largest ichthyosaur vertebrae. Credit: © Rosi Roth / University of Zurich

The rocks from which these fossils originate, known as the Kössen Formation, once lay at the bottom of a shallow coastal area – a very wide lagoon or shallow basin.

This increases the uncertainty surrounding the habits of these animals, the size of which indicates their suitability for deeper parts of the sea. “We think the great ichthyosaurs followed schools fish into the lagoon. The fossils can also originate from orphans who died there “, Furrer suggests.

“You have to be a kind of mountain goat to access the relevant beds,” laughs Sander. “They have the annoying property of not occurring below about 8,000 feet, well above the tree line.”

95 million years ago, the northeastern part of Gondwana, the African plate (of which the Kössen Formation was a part), began to press against the European plate, which ended with the formation of very complex piles of different rock units (called “nappes”) in the alpine orogeny about 30–40 million years ago, ”says Furrer. So it is that these rude scientists found themselves picking through the frozen cliffs of the Alps and draging pieces of ancient marine monsters almost down to sea level again to get into the scientific document.

Implications of test PIMUZ A / III 670:

  1. Many of the giant ichthyosaurs from sentrias seem to have no teeth. The only safe exception is Himalayasaurus (Motani et al., 1999) and the tooth PIMUZ A / III 670 described in this study.
  2. Together with the scanty but morphologically different tooth material in the Himalayan Saurus, the tooth suggests the existence of a variety of giant tooth-bearing ichthyosaurs in the late Triassic.
  3. The finding underscores the notion that the late Triassic tyosaurs were clearly larger than the more familiar Jurassic forms.

“The fossils described in this article underscore the global distribution and ecological diversity of giant Norian and Rhaetian ichthyosaurs and the deep faunal turnover among ichthyosaurs at the end of the Triassic.” The study ends.

Journal reference

  1. P. Martin Sander, Pablo Romero Pérez de Villar, Heinz Furrer & Tanja Wintrich. Giant ichthyosaurs from sentries from the Kössen Formation in the Swiss Alps and their paleobiological implications. Journal of Vertebrate PaleontologyDOI: 10.1080 / 02724634.2021.2046017


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