Shonisaurus (Nobu Tamura).


Shonisaurus (Greek for "Shoshone mountain reptile"); pronounced SHOW-nee-SORE-us


Oceans worldwide

Historical Period:

Late Triassic (215 million years ago)

Size and Weight:

About 50 feet long and 30 tons


Fish, squid and cephalopods

Distinguishing Characteristics:

Large, thick trunk; large eyes; sharp teeth embedded in a narrow snout


About Shonisaurus

Shonisaurus was among the strangest and most imposing of all ichthyosaurs ("fish lizards"): it looked a bit like a cross between a dolphin and a whale, given its thick, round body, long, narrow front and rear flippers, pointed snout with teeth only on the front end, and double-pronged, hydrodynamic tail.

At upwards of 50 feet long and 30 tons, this was one of the biggest animals on the planet during the late Triassic period, about 215 million years go, matched in size only by the giant marine reptiles and fish that dominated the world's oceans tens of millions of years later, such as Liopleurodon and Leedsichthys.

Like other ichthyosaurs, Shonisaurus is believed to have evolved from land-dwelling reptiles that returned to an aquatic lifestyle during the early Triassic period (shortly before their terrestrial companions, the archosaurs, started evolving into the very first dinosaurs); the ichthyosaurs as a whole were subsequently rendered extinct, at the end of the Jurassic period, by even better-adapted plesiosaurs and pliosaurs. Oddly enough, Shonisaurus also happens to be the state fossil of land-locked Nevada, which was submerged beneath a shallow body of water, the Western Interior Sea, during much of the Mesozoic Era; 37 separate fossil specimens have been recovered from this state's Shoshone Mountains.

No discussion of Shonisaurus would be complete without a reference to the "Triassic Kraken," one of the more amusing recent forays into cryptozoology. In 2011, two geologists from Mount Holyoke College stated that the remains of a Shonisaurus specimen had mysteriously been arranged, at the bottom of what was then the Western Interior Sea, in a tentacle-like pattern, and proposed that an even more massive octopus with advanced intelligence was responsible for this prehistoric work of art.

The trouble is, the distribution of these fragmented remains is open to competing interpretations, and it's a completely unwarranted leap to propose the existence of a 50-ton, big-brained cephalopod, especially when there's absolutely no direct fossil evidence that this beast existed!

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Your Citation
Strauss, Bob. "Shonisaurus." ThoughtCo, Jan. 24, 2017, Strauss, Bob. (2017, January 24). Shonisaurus. Retrieved from Strauss, Bob. "Shonisaurus." ThoughtCo. (accessed November 19, 2017).