Large ichthyosaurs are nothing new for Nevada. Our state fossil is the giant ichthyosaur Shonisaurus popularis, the bones of which are on display at Berlin-Ichthyosaur State Park in central Nevada. We have a replica of Shonisaurus on display at the Las Vegas Natural History Museum. But there is now another giant ichthyosaur in Nevada’s paleontological portfolio. A paper published last month in the high-profile, peer-reviewed journal Science describes a whale-size ichthyosaur more than fifty feet long from the Middle Triassic of northwestern Nevada. It’s about 246 million years old―a few million years older than Shonisaurus. The photo shows just the head, which is the size of a grand piano. Its name is Cymbospondylus youngorum. It was the largest known animal to exist at the time, and the first in a series of marine giants, including whales, which evolved about 200 million years later.
Paleontologists are curious about why huge ichthyosaurs evolved in the Triassic. The really exciting aspect of the new study concerns the short time it took for this huge marine reptile to evolve. Ichthyosaurs first appeared 249 million years ago, shortly after the largest known extinction event in Earth history―the end Permian mass extinction―which reset the structure of marine and terrestrial ecosystems. Early in the Triassic Period the oceans contained abundant small (such as conodonts) and medium-size (such as ammonoids) animals, but no large carnivores. This situation apparently created an opportunity for amazingly large ichthyosaurs such as Cymbospondylus and Shonisaurus to rapidly evolve. The newly described giant, Cymbospondylus youngorum, evolved in just three million years after the first appearance of ichthyosaurs on Earth. That is really fast evolution! Fossils of Nevada continue to fascinate us and contribute to our exploration of the history of life.
Pictured here is ichthyosaur Shonisaurus popularis, as seen on display in our Prehistoric Gallery.
Thank you Dr. Rowland for this exciting Fossil Friday!