One rare exception — discovered in the 1800s in southern England's Bristol Channel — is a spectacularly preserved, 180 - million - year - old ichthyosaur named Hauffiopteryx.
Mary Anning and her brother Joseph found the complete skeleton of a Jurassic - era ichthyosaur in 1812; the creature (which was thought to resemble a crocodile) didn't receive its current scientific name until 1817.