New study shows fossil finds in the Hautes Alpes come from three giants of the seas

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More than 30 years ago, researchers from the University of Zurich discovered vertebrae, ribs and a tooth in the High Alps of eastern Switzerland. The typical form indicated that they must have originated from large marine reptiles known as ichthyosaurs, but there was a lack of corresponding comparative material. A new study conducted by the University of Bonn now allows a more precise classification. According to the findings, they belong to three different ichthyosaurs of about 15 to about 20 meters in length. The tooth is particularly unusual: with a root diameter of six centimeters, it is twice as large as the largest aquatic dinosaur tooth found to date. The results have just been published in the Journal of Vertebrate Paleontology.

The first ichthyosaurs crossed the primordial oceans in the early Triassic about 250 million years ago. They had an elongated body and a relatively small head. But shortly before most of them died out around 200 million years ago (only familiar dolphin-like species survived until 90 million years ago), they evolved to gigantic shapes. With an estimated weight of 80 tons and a length of more than 20 meters, these prehistoric giants would have rivaled a sperm whale. However, they left few fossil remains – “why it remains a great mystery to this day”, emphasizes Professor Dr. Martin Sander from the paleontology section of the Institute of Geosciences at the University of Bonn.

The folding of the Alps brought up fossils from the bottom of the sea

The finds examined today come from Graubünden (canton of Graubünden). Sander’s colleague, Dr. Heinz Furrer of the University of Zurich, had recovered them with students between 1976 and 1990 during geological mapping of the Kössen Formation. More than 200 million years ago, rock layers with fossils still covered the seabed. With the folding of the Alps, however, they had found themselves at an altitude of 2,800 meters. “Maybe there are more remains of giant sea creatures hiding under the glaciers,” Sander hopes.

The paleontologist first held the fossilized bones in his hands three decades ago. At that time he was still a doctoral student at the University of Zurich. In the meantime, the material had been somewhat forgotten. “Recently, however, other remains of giant ichthyosaurs have appeared,” explains the researcher. “It therefore seemed interesting to us to analyze the Swiss finds in more detail again.”

According to the study, the fossils come from three different animals that lived around 205 million years ago. From one of the ichthyosaurs, a vertebra is preserved with ten fragments of ribs. Their sizes suggest that the reptile was probably 20 meters long. In contrast, only a set of vertebrae were extracted from a second ichthyosaur. Comparison with better preserved skeletal finds suggests a length of around 15 meters.

“From our perspective, however, the tooth is particularly exciting,” says Sander. “Because it’s huge by ichthyosaur standards: its root was 60 millimeters in diameter – the largest specimen still in a complete skull to date measured 20 millimeters and was from an ichthyosaur that was almost 18 meters long .” His colleague Heinz Furrer is delighted with the belated appreciation of the spectacular remains from the Swiss Alps: “The publication has confirmed that our findings at the time belonged to the longest ichthyosaur in the world; with the thickest tooth found to date and the largest trunk vertebra in Europe!”

However, the animals that populated the primordial oceans 205 million years ago are unlikely to have lived much longer than previously thought. “The diameter of the tooth cannot be used to directly deduce the length of its owner,” emphasizes paleontologist Martin Sander from Bonn. “Still, the discovery naturally raises questions.”

Predators larger than a sperm whale aren’t really possible

Indeed, research assumes that extreme gigantism and a predatory lifestyle (which requires teeth) are incompatible. There’s a reason the largest animal of our time is toothless: the blue whale, which can be up to 30 meters long and weigh 150 tons. Next to it, the toothed sperm whale (20 meters and 50 tons) looks like a teenager. While the blue whale filters out tiny water creatures, the sperm whale is a perfect hunter. This means that he needs more of the calories he consumes to fuel his muscles. “So marine predators probably can’t get much bigger than a sperm whale,” says Sander.

So it’s possible that the tooth didn’t come from a particularly gigantic ichthyosaur — but from an ichthyosaur with particularly gigantic teeth.

Participating establishments:

The Department of Paleontology of the Institute of Geosciences of the University of Bonn, the Institute and Museum of Paleontology of the University of Zurich and the Institute of Anatomy of the University of Bonn participated in the study.

Source of the story:

Material provided by University of Bonn. Note: Content may be edited for style and length.

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