Mesozoic marine reptiles

Jules Verne

In 1867, Jules Verne published his famous novel Journey to the Center of the Earth, whose protagonists discover an underground ocean at great depth, which they baptize as the Liddenbrock Sea, and witness the fight to the death of two great marine animals: a plesiosaur and an ichthyosaur, supposed descendants of ancestors that sank with the Liddenbrock Sea a hundred million years before and survived down there, protected by the Earth's crust, while their surface congeners became extinct as a result of the impact of the meteorite or comet that put an end to most dinosaurs, although that was not known in Verne’s time. But what were those plesiosaurs and those ichthyosaurs that populated the seas during the Mesozoic, formerly called the Secondary Era?

At the dawn of the age of dinosaurs, the oceans of the Earth were joined in a single sea, Panthalassa, which surrounded the supercontinent Pangaea. In that global ocean, at the beginning of the Triassic period, ichthyosaurs appeared. Since the Jurassic, and during the rest of the Mesozoic, Pangaea gradually fragmented, giving rise to new seas.