It is possible that 'dragons' are just the last of the dinosaurs roaming the earth before they were all killed off. You will not find a credible reference as there is no 'dragon' skeleton laying in a museum any where in the world. But there are dinosaur bones in museums around the world. It is a little like the woolly mammoth, lots of cave drawings, but no bones until recent years. All we had to go on was an elephant. The lockness monster is possibly another example of a dinosaur living out its last days, long since gone but the legend lives on. Then you have tales of knights and dragons which have evolved over the years. Look at witches - they were just herbalists, naturalists, early doctors and consider the reputation they ended up with. Who knows maybe there once was a dragon creature. There once was a saber tooth tiger, a Tasmainian tiger, a dodo bird, the list goes on.