Shonisaurus

Shonisaurus is a genus name basically meaning "Lizard from the Shoshone Mountains." There are two identified species, S. popularis and S. sikanniensis. The first of those was discovered in the Shoshone Mountains near Berlin, Nevada in 192. While Nevada is now dry, back in the Late Triassic the entire area was underwater. 37 specimens were found at that site, (one theory is that they all beached together) with excavations under Dr. Charles Camp of UC-Berekley taking place in the 1950s and 60s. The second species was discovered in British Columbia, Canada in the 1990s.

(Image Source)

Shonisaurus is one of the oldest and largest Ichthyosaurs ever discovered. It is rivaled in size only by sea dwellers that existed tens of millions of years after it. The largest Shonisaurus specimens, those of S. sikanniensis were estimated to be 21m long. S. popularis was a bit smaller, at around 15m. Both species lived during the late Triassic between 225 and 208 million years ago.

(Image Source)

Shonisauruses were predators. Their mouths contained teeth, but only at the front end, and their skulls were up to 3m long. They possessed long, narrow flippers in both front and back. They had streamlined bodies and powerful tails for movement underwater.

There is an interesting story that miners actually discovered Shonisaurus back in the 1860s, and used their vertebrae as dinner plates until scientists swooped in decades later and told them what they had. Alas, this story is a myth, with origins possibly residing with a description by Dr. Camp of the eyes being as large as dinner plates.