The two-meter skull of a newly discovered giant ichthyosaur species, the oldest known, is shedding new light on the rapid growth of the first marine reptiles.
While dinosaurs ruled the land, ichthyosaurs and other aquatic reptiles (which weren’t dinosaurs) ruled the waves, reaching equally gigantic sizes and species diversity. With evolving fins and hydrodynamic body shapes seen in both fish and whales, ichthyosaurs swam in ancient oceans for almost the entirety of the Age of Dinosaurs.
Excavated from a rock unit called the Fossil Hill Member in the Augusta Mountains of Nevada, the well-preserved skull, along with part of the spine, shoulder, and front fin, date back to the Middle Triassic (247.2-237 million ago years) representing the first case of an ichthyosaur to reach epic proportions.
As big as a large sperm whale over 17 meters long, the newly named Cymbospondylus youngorum is the largest animal discovered so far in that time period, on land or in the sea. In fact, it was the first giant creature that we know of to inhabit the Earth, as explained in a statement by the paleontologist at the University of Bonn and a researcher at the Dinosaur Institute at the Natural History Museum of Los Angeles County (NHM).
In other Nevada mountain ranges, paleontologists have been recovering limestone, shale, and siltstone fossils from the Fossil Hill Member since 1902, opening a window to the Triassic. Mountains connect our present with ancient oceans and have produced many species of ammonites, shelled ancestors of modern cephalopods such as cuttlefish and octopus, as well as marine reptiles. All of these animal specimens are collectively known as Fossil Hill Fauna, and represent many of C. youngorum’s prey and competitors.
C. youngorum stalked the oceans about 246 million years ago, or only about three million years after the first ichthyosaurs wet their fins, a surprisingly short time to get that big. The elongated snout and conical teeth suggest that C. youngorum preyed on squid and fish, but its size meant that it could also have hunted smaller, juvenile marine reptiles.
The giant predator probably had some stiff competition. Using a sophisticated computational model, the authors examined the probable energy running through the food web of Fossil Hill Fauna, recreating the ancient environment through data, and found that marine food webs could support some more colossal carnivorous ichthyosaurs. .
Ichthyosaurs of different sizes and survival strategies proliferated, comparable to modern cetaceans, from relatively small dolphins to filter-feeding baleen whales and giant squid-hunting sperm whales.
