The central figures are a large ichthyosaur biting into the long neck of a plesiosaur. The sea was occupied by mosasaurs, ichthyosaur, and plesiosaurs. A parallel convergence occurred with the now extinct marine reptile ichthyosaur. Few ichthyosaur fossils are known from the Middle Jurassic. Vertebrate fossils, such as ichthyosaur skeletons, sold for more, but were much rarer. In 1816, he described ichthyosaur fossils owned by William Buckland and James Johnson. In 1977, the Triassic ichthyosaur "Shonisaurus" became the state fossil of Nevada. A parallel convergence occurred with the now extinct ichthyosaur. Ichthyosaur fore and hind limbs had been fully transformed into flippers. During the nineteenth century, the number of described ichthyosaur genera gradually increased. With ichthyosaur teeth, the dentine shows prominent vertical wrinkles. About half of the ichthyosaur genera today seen as valid were described after 1990. Ultimately, over four thousand were uncovered, forming the bulk of ichthyosaur specimens displayed today. The biologist Stephen Jay Gould said the ichthyosaur was his favourite example of convergent evolution. The biologist Stephen Jay Gould said the ichthyosaur was his favorite example of convergent evolution.