Fossils of giant marine reptiles found high in the Swiss Alps

By Will Dunham

– Fossils from some of the largest creatures ever to swim Earth’s oceans – whale-sized marine reptiles called ichthyosaurs – have been found in a counterintuitive place: atop three mountains in the Swiss Alps up to 8,990 feet (2,740 meters) above sea level.

Scientists on Thursday described rib and vertebrae fossils from two ichthyosaur individuals: one about 69 feet (21 meters) long and the other about 49 feet (15 meters). They described from a third individual the largest-known tooth from any ichthyosaur with a base 2.4 inches (6 cm) wide and an estimated length of 6 inches (15 cm), 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 https://www.tandfonline.com/doi/full/10.1080/02724634.2021.2046017.

It was found atop the Chrachenhorn mountain near Davos. Based on the fact that a 59-foot-long (18-meters-long) ichthyosaur described last year had a tooth with a base eight-tenths of an inch (2 cm) wide, Sander said, “then a tooth 6 centimeters wide could possibly have come from an animal 54 meters (177 feet) 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 co-author 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.

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 69 feet (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 98 feet (30 meters) long, has been considered Earth’s largest-ever creature. Sander said future research on giant Triassic ichthyosaurs may challenge this conclusion.