This behemoth was one of the biggest fish ever to live. People think it is a whale, although it lived before mammals like whales dominated the seas, so it is not a whale. It was discovered near lake Shasta (a lake in Northern California, which is right next to a non-active volcano) this massive icthyosaur could grow up to 70 feet long, which would make an adult blue whale just a bit larger compared to this prehistoric beast. It lived during the late Triassic and was named after the non-active volcano Mount Shasta which overlooks lake Shasta, where it was found near.