How can a fossil plesiosaur (a creature that lived in the ocean) have been found in Wiltshire, miles from the sea?

150 million years ago, when dinosaurs were alive, Wiltshire was under a shallow sea. In fact the world looked completely different from what it does now. The familiar outlines of Europe, Africa and all the other continents did not exist at this stage as the Earth was changing quite drastically. So dinosaurs are often found in areas where we might not now expect to see them.