The two-meter-high skull of the newly discovered giant ichthyosaur species, the oldest known, sheds new light on the rapid growth of the first marine reptiles.
While dinosaurs ruled the Earth, ichthyosaurs and other aquatic reptiles (that weren’t dinosaurs) ruled the waves, reaching gigantic sizes and species diversity. With the evolution of the fins and hydrodynamic body shapes seen in both fish and whales, ichthyosaurs swam in ancient oceans for nearly the entire age of the dinosaurs.
Excavated from a rock unit called Fossil Hill Member in the Augusta Mountains of Nevada, the well-preserved skull, along with part of the spine, shoulder and front fin, dates back to the Middle Triassic (247.2-237 million years ago) representing the first case of an ichthyosaur to reach Epic proportions.
At the size of a large sperm whale of over 17 metres, Cymbospondylus youngorum is the largest animal discovered so far in that time period, on land or at sea. In fact, it was the first giant creature we know to inhabit Earth, as explained in a statement by a paleontologist at the University of Boone and a researcher at the Dinosaur Institute at the Los Angeles County Museum of Natural History (NHM).
In other Nevada mountain ranges, paleontologists have been recovering limestone, shale and mudstone fossils from the Fossil Hill member since 1902, opening a window into the Triassic. Mountains connect our present with ancient oceans and have produced many species of ammonites, the scaled ancestors of modern cephalopods such as squid and octopus, as well as marine reptiles. All of these animal specimens are collectively known as Fossil Hill fauna, and represent many of Jim Youngorum’s prey and its competitors.
C. youngorum chased the oceans about 246 million years ago, or only about three million years after the first ichthyosaurs wetted their fins, a surprisingly short time to get this big. Its elongated nose and conical teeth indicate that C. youngorum preyed on squid and fish, but its size means that it can also hunt smaller marine reptiles and juveniles.
Perhaps the giant predator had some stiff competition. Using a sophisticated computational model, the authors examined potential energy passing through the food web of Fossil Hill Fauna, recreating the ancient environment through data, and found that marine food webs could support some of the massive carnivorous ichthyosaurs.
Similar to modern cetaceans, ichthyosaurs of varying sizes and survival strategies proliferated from relatively small dolphins to filter-feeding baleen whales and giant squid-hunting sperm whales.
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