Paleontologists have discovered rare fossils from ancient sea creatures that grew to enormous lengths of more than 65 feet—making them among the biggest animals ever to roam our planet—strewn across the slopes of the Swiss Alps, at elevations of nearly two miles above sea level, reports a new study. Remarkably, one of the fossils is the largest tooth ever discovered from these massive creatures, which are called ichthyosaurs.
Ichthyosaurs are not as famous as the world’s other major behemoths: Whales and the long-necked dinosaurs called sauropods. This is in part because fossils of these Triassic Period giants are so scarce, though their smaller descendants are more commonly found later in the fossil record.
That’s why scientists led by Martin Sander, a paleontologist at the University of Bonn in Germany, emphasized the importance of newly-described remains of giant ichthyosaurs found decades ago at high alpine altitudes. The fossils include vertebrae, ribs, and an extremely special tooth, which are sourced from three distinct animals and together confirm that “the Late Triassic global seas harbored whale-sized ichthyosaurs about which we know very little regarding their size, morphology, and lifestyle,” according to a study published on Thursday in the Journal of Vertebrate Paleontology.
“Basically, this is like a piece of the puzzle,” Sander said in a call. “The Triassic is this time period that is really, for many paleontologists, the most exciting because it's the origin of the modern world.”
After life on Earth nearly completely died out at the end of the Permian Period, it “came back with a vengeance” during the Triassic Period, he added. “We get super-fast evolution of giant size [in ichthyosaurs] and they stayed large for the next 40 million years. The problem is that for the last 30 million years of the Triassic, we have a miserable record.”
The specimens help to fill in this frustrating gap in the fossil record, providing an unprecedented snapshot into the waning era of the giant ichthyosaurs, before the family shrank to about the size of dolphins for the remainder of the dinosaur age.
“We have 30 million years of a black hole and that is the problem,” said Sander. “There is no other time period or any ecosystem that is so poorly represented for the entire history of multicellular life, and that's where those first of the giants evolved or lived.”
The fossils were originally collected between 1976 and 1990 during alpine expeditions led by Heinz Furrer, a retired curator at the University of Zurich’s Paleontological Institute and Museum and a co-author of the study, but their importance has only become clear in recent years as scientists have unearthed giant ichthyosaurs in other parts of the world, such as British Columbia and the Himalayas.
Almost all of the giant sea creatures that have been discovered were toothless, probably because they were suction feeders that consumed small animals in great quantities. This is a common strategy for enormous creatures: For instance, the largest whales in the sea feed on tiny species like krill, while the sauropod dinosaurs, the biggest land animals of all time, were herbivores.
For this reason, the discovery of the ichthyosaur tooth is particularly exciting because it suggests that the family also included unusually big predators during the Late Triassic. The fossil is more than two inches wide at the base, making it by far the biggest ichthyosaur tooth ever found. While it's possible that this belonged to a smaller ichthyosaur that happened to have freakishly large teeth, the team thinks it may also indicate that these ancient predators could approach the 60-foot scales of their toothless brethren, which would make them an outlier not only for this time period, but in all of evolutionary history.
“That tooth was always special,” Sander said. “You can't really tell what kind of ichthyosaur it is, but the crucial bit is you can tell that it's an ichthyosaur, because ichthyosaurs have very special teeth” that are distinguishable by grooved dentin patterns at their roots.
“Those that we find in the Alps are really kind of ghosts,” he added. “We know they are there. We know they're giant—by far the largest ichthyosaur tooth is floating around—but that's all we have for the animal.
That said, paleontologists like Sander are now, with mixed feelings, capitalizing on a new trend that may expose more precious fossils from the Triassic giants: Human-driven climate change. As glaciers at high altitudes recede, it presents a unique opportunity to search for the remains of the creatures that lived in these prehistoric oceans.
“It's terrible to see the glaciers melting in the Alps,” Sander emphasized. “But the good thing is where the glaciers were, is where our fossiliferous beds are now. That was one incentive for me to go up to the mountains, in late 2020, just to see this for myself. And yes, there are more fossils coming up under the glaciers.”
Future discoveries might help to raise the profile of these Triassic leviathans to the level of modern blue whales, the biggest animals of all time, or the Jurassic sauropods who remain unrivaled in size on land to this day.
“It's an emerging story,” Sander said. “It's all rapidly unfolding.”