Many have often connected dragons to dinosaurs; for instance, crocodiles are considered cousins to the dinosaur branch.  When describing dragons, many dinosaur-like things pop up. Examples include the large teeth, reptilian appearance, living areas (depending on both dragon and dinosaur), size, and shape.
There is a good deal of evidence that one could argue about dragons being dinosaurs. Some seven hundred species have been found as of yet, and more are being discovered.  These creatures vary in shape, size, eating habits, habitats, and personality, much like dragons. As a matter of fact, dinosaurs are lumped into one category in the same way that dragons are, namely for the purpose of study.
There are many arguments over dinosaurs. Were the warm-blooded or cold-blooded? Have birds descended from them? Did man, or a man-like creature, live during the time of dinosaurs? Why and how did they die out? How did they evolve? How did their bodies function?
Then one can review the various sea dinosaurs, many of which are believed to survive to this day somehow. They are described much like dragons; huge, carnivorous, elusive, and serpent-like. Why is it that dinosaurs resemble dragons today?
Many believe that man did not live during the time of dinosaurs, which means that dragons came about by some other means, but it has been argued that dragons are dinosaurs.