Fossils of some of the largest creatures to ever swim in Earth’s oceans – whale-sized marine reptiles called ichthyosaurs – have been discovered 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 fossil ribs and vertebrae 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 of any ichthyosaur with a base 2.4 inches (6 cm) wide and an estimated length of 6 inches (15 cm), suggesting a fearsome predator.
The fossils, dating from around 205 million years ago towards 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 the Earth,” said paleontologist Martin Sander from 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.
He was found on top of the Chrachenhorn mountain near Davos. Based on the fact that a 59-foot (18-meter-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 come from an animal 54 meters (177 feet) long.”
The animal was probably not that big but still formidable, perhaps sperm whale-like, hunting giant squids, large fish, and smaller ichthyosaurs. Some other giant ichthyosaurs apparently lacked teeth and ate small fish and squid, sucking them in or engulfing them in their mouths.
Giant ichthyosaurs – the largest marine reptiles of all time – had elongated bodies, with relatively small skulls.
The fossils were discovered in the 1970s and 1980s at three sites in Switzerland’s Eastern Alps, said study co-author Heinz Furrer, a retired curator at the University’s Institute and Museum of Paleontology. from Zurich, who discovered them with other geology students at the time. . Fossils are described scientifically for the first time.
The inexorable movement of the huge plates that make up the earth’s crust in a process called plate tectonics explains how fossils that formed on an ancient seabed found their way to the tops of mountains.
“The Alps have a very complicated structure, with giant slabs of rock made up of ancient seabed, called nappes, piled on top of each other by the African plate pushing into the European plate. The nappe from which the ichthyosaurs originated is tallest in the world. This stacking has happened over the last 35 million years or so,” Sander said.
The remains are too incomplete to definitively determine their species but likely belong to a family of ichthyosaurs called Shastasauridae. This family includes the largest 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 were not known from so close to the end of the Triassic. They apparently went extinct during the mass extinction event at the end of the Triassic around 201 million years ago – and no sea creatures became so large again until baleen whales there about 3 million years old. Small 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: the Triassic ichthyosaurs, which came first but remain mere ghosts; long-necked sauropod dinosaurs on land; and baleen whales today,” Sander said.
Today’s blue whale, measuring up to around 98 feet (30 meters) long, has been considered the largest creature on Earth. Sander said future research on giant Triassic ichthyosaurs may challenge that conclusion.