Meet the Mount Shasta Lizard: The Largest Known Marine Reptile to Ever Live on Earth

Illustration of what the Shastasaurus might look like

In 1893, James Perrin Smith of Stanford University participated in a fossil-collecting expedition to the Triassic Hosselkus Limestone in northern California in the areas between Squaw Creek and the Pit River. He returned with the bones of a marine reptile he believed to be a Nothosaurusbut within the next decade they concluded that it was a new species – the largest marine mammal ever known to live on land.

Thus, the Shastasaurus was discovered, aptly named after nearby Mount Shasta.

Upper Triassic limestone exposures, Hosselkus, on Brock Mountain, Shasta County, California. The location of the first Shastasaurus fossils.

The Shastasaurus, also known as the Mount Shasta lizard, lived on earth around 210 million years ago during the Triassic Period and could grow up to 75 feet long. While dinosaurs roamed the land, this marine reptile ruled the ocean in a strange way, using its short, toothless snout as a very powerful vacuum cleaner, consuming mostly soft-bodied cephalopods in the ocean.

Shastasaurus was long and slender, with its ribcage measuring 6 feet wide despite being 23 feet long. The creature’s characteristics and habits are still debated in the scientific community, but we do know one thing about Shastasaurus: it was massive.

Shastasaurus perrini, UCMP 9119, from Merriam’s 1908 paper on the Triassic ichthyosaur, with special reference to American forms.

Since its discovery in the late 1800s, Shastasaurus has become a well-known genus of ichthyosaur found throughout the world. Scientists have since realized that two other ichthyosaurs – one in China and another in Canada – were also part of the Shastasaurus family.

As scientists and paleontologists continue to gather information and classify these animals millions of years ago, there are still many questions about what led to Shastasaurus’s demise. But one thing is for sure, the largest marine reptile once called northern California home.

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