Fossils of giant marine reptiles found high in the Swiss Alps

Marcello Perillo / University of Bonn via Reuters
A giant ichthyosaur from the Late Triassic bulk-feeding on a school of squid is seen in an undated artist’s rendering.

Fossils from some of the largest creatures ever to swim Earth’s oceans — whale-size marine reptiles called ichthyosaurs — have been found in a counterintuitive place: atop three mountains in the Swiss Alps up to 2,740 meters above sea level.

Scientists on April 28 described rib and vertebrae fossils from two ichthyosaur individuals: one about 21 meters long and the other about 15 meters. They described from a third individual the largest-known tooth from any ichthyosaur with a base 6 centimeters wide and an estimated length of 15 centimeters, suggestive of a fearsome predator.

The fossils, dating to around 205 million years ago near the end of the Triassic Period, make these three individuals among the largest of the giant ichthyosaurs that inhabited the oceans at a time when dinosaurs were beginning to dominate the land.

“The tooth is particularly interesting because it could possibly — but unlikely — represent the largest animal to ever inhabit Earth,” said paleontologist Martin Sander of the University of Bonn, lead author of the study published in the Journal of Vertebrate Paleontology.

It was found atop the Chrachenhorn mountain near Davos, Switzerland. Based on the fact that an 18-meter-long ichthyosaur described last year had a tooth with a base 2 centimeters wide, Sander said, “then a tooth 6 centimeters wide could possibly have come from an animal 54 meters in length.”

The animal likely was not that big but still formidable, perhaps akin to a sperm whale, hunting giant squid, large fish and smaller ichthyosaurs. Some other giant ichthyosaurs apparently lacked teeth and ate small fish and squid, sucking them up or engulfing them in their mouths.

The giant ichthyosaurs — the largest-ever marine reptiles — had elongated bodies, with relatively small skulls.

The fossils were found in the 1970s and 1980s at three sites in the eastern Alps in Switzerland, said study coauthor Heinz Furrer, a retired curator at the University of Zurich’s Paleontological Institute and Museum who discovered them along with other geology students at the time. The fossils are being described scientifically for the first time.

Jelle Heijne / University of Bonn via Reuters
Researchers, including Martin Sander, look over the geological layers where remains of ichthyosaurs were found on the southern slope of a mountain called Schesaplana in the Swiss High Alps in this undated handout image.

The inexorable movement of the immense plates that make up Earth’s crust in a process called plate tectonics explains how fossils that formed in an ancient seabed ended up atop mountains.

“The Alps have a very complicated structure, with giant slabs of rock consisting of former seafloor, called nappes, piled on top of each other by the African plate pushing into the European plate. The nappe that the ichthyosaurs come from is the highest in the pile. This piling up happened in the last 35 million years or so,” Sander said.

The remains are too incomplete to definitively determine their species but probably belong to an ichthyosaur family called Shastasauridae. This family includes the biggest-known ichthyosaur: Shastasaurus, with a specimen from Canada indicating a length of 21 meters.

Some researchers have proposed longer ichthyosaur lengths based on partial fossils.

Until now, giant ichthyosaurs had not been known from so near the end of the Triassic. They apparently disappeared in the mass extinction event at the conclusion of the Triassic about 201 million years ago — and no marine creatures got as big again until baleen whales about 3 million years ago. Smaller ichthyosaurs lived until about 90 million years ago.

“There were three groups of animals in the history of life on Earth that were true giants: ichthyosaurs of the Triassic, which came first but remain mere ghosts; long-necked sauropod dinosaurs on land; and today’s baleen whales,” Sander said.

Today’s blue whale, up to about 30 meters long, has been considered Earth’s largest-ever creature. Sander said future research on giant Triassic ichthyosaurs may challenge this conclusion.