At the same time as dinosaurs lived on land, there were giant reptiles in the oceans. These were not closely related to dinosaurs, but they were no less spectacular.
One of the earliest was the Ichthyosaur. It had flippers and a long snout, just like dolphins do today. It had a fin on its back, just as fish do. But it wasn't related to either, for it was a reptile. These are simply the kinds of things fast-moving creatures need in the sea. Eventually ichthyosaurs died out and were replaced by plesiosaurs.
