The fossils of the “fish lizard” found in the Swiss Alps belong to some of the largest creatures that have ever lived

About 200 million years ago, those rock layers were the floor of a vast lake.

“We believe large ichthyosaurs followed the lake’s fish shoals. The fossils may also have derived from electrolytes that died there,” study co-author Heinz Furer, retired curator at the University of Zurich’s Institute and Museum of Paleontology, said in a statement.

But the Alpine folding, which began 95 million years ago when the African tectonic plate began to push against the European tectonic plate, created piles of rock layers about 30 to 40 million years ago. The fossils were “tectonically deformed,” crushed by the motions of the tectonic plates that pushed them into a rocky formation atop a mountain.

The study’s lead author, B. “You have to be a kind of mountain goat to get to the related family,” Martin Sander, professor of vertebrate palaeontology at the University of Bonn in Germany, said in a statement. “They have the annoying property of not occurring below about 8000 feet (2438.4 metres), well above the tree line.”

Although these creatures once ruled the seas, fossils are rare, creating a huge mystery for paleontologists. But the remains of these ichthyosaurs have shed new light on these mysterious, extinct creatures.

One big tooth

The fossils belong to three different types of ichthyosaurs. One was about 65 feet (20 meters) long, while the other was 49 feet (15 meters) long. But the most exciting discovery associated with these fossils is the largest ichthyosaur tooth ever found.

“This is huge by ichthyosaur standards: its root diameter was 60 mm – the largest specimen still in a complete skull so far was 20 mm and came from an ichthyosaur that was about 18 meters (59 ft) long,” Sander said.

Scientists know that smaller ichthyosaurs had teeth, but most giants were toothless, and were supposed to have fed on cephalopods, such as squid, through suction.

The giant toothed ichthyosaurs likely resembled sperm whales and killer whales today, and used their teeth to capture prey like giant squid.

But the tooth is a challenge because it fractured at the crown. While researchers know it was an ichthyosaur tooth due to unique features, such as the implantation of ivory into the root of the tooth, they cannot be sure that the tooth’s size reflects the animal’s size.

“It is difficult to determine whether the tooth was from a large ichthyosaur with giant teeth or from a giant ichthyosaur with medium-sized teeth,” Sander said.

That’s because, according to researchers, being giant and being a predator (with teeth) don’t line up — which is why the blue whale, which weighs 150 tons and can reach 98 feet (30 meters) in length, doesn’t have any teeth. Instead, it filters the tiny creatures out of the water.

Meanwhile, sperm whales, which weigh 50 tons and are 65 feet (20 meters) long, are hunters.

“It’s possible that marine predators couldn’t get much bigger than the sperm whale,” Sander said.

Giants in the mountains

The fossils were first discovered during geological mapping of the Alps between 1976 and 1990. Forer was part of the original team that retrieved fossils from the rock, known as the Kössen Formation, and remembers holding the fossils in hand when he was a doctoral student at the University of Zurich.

Over time, the fossils were largely forgotten.

“Recently, more remains of giant ichthyosaurs have appeared,” Forer said. “So it seemed to us useful to analyze the Swiss finds again in more detail as well.”

Fossils of ichthyosaurs have been found all over the world, but the remains of a giant species have been concentrated in North America. Finding these specimens in modern Switzerland expands their range.

Previous evidence had suggested that some of them could be as large as blue whales, the world’s largest animal.

“In Nevada, we see the beginnings of true giants, and in the Alps we see the end,” Sander said. “Only dolphin of medium to large size—and orca-like forms—survived into the Jurassic (period),” between 145 and 201 million years ago.

Sander wonders if there are more “giant marine creatures hidden under the glaciers.” But these fossils help fill a knowledge gap about giant marine lizards.

“It is a huge embarrassment to paleontology that we know so little about these giant ichthyosaurs despite the extraordinary size of their fossils,” Sander said. We hope to rise to this challenge and find new and better fossils soon.