Shonisaurus in the Shoshone Greek meaning “mountain reptile”, this dinosaur can be found throughout the world’s oceans. It has about 50 meters long and 30 tonnes in weight. Life in the Late Triassic period (215 million years ago).
Shonisaurus eating fish and squid in the ocean. looks a little like a cross between a dolphin and a whale with a thick, rounded body, a long, narrow front and rear fins, pointed mouth with teeth only in the front end, and a double-pronged tail.
It is one of the largest animals on the planet during the late Triassic period, matched in size only by the giant marine reptiles and fish that lived tens of millions of years later, especially Liopleurodon and Leedsichthys.
Like other ichthyosaurs, Shonisaurus believed to have evolved from terrestrial lizards were returned to the water lifestyle during the early Triassic period. Which makes this family of marine reptiles roughly analogous to modern dolphins and whales, which also evolved from small, terrestrial ancestors. (By the way, Shonisaurus is fossil-locked state of Nevada, which is submerged under a shallow body of water for more than the Mesozoic Era.)