So if they believe the flood happened because so many cultures have flood stories. Then by the same stroke they most also believe that dragons walk the earth.
Why not dragons? No one seriously denies that dinosaurs walked the earth.
Besides, let's suppose that smaller dinosaurs -- about the size of the very large mammals of today -- were represented in Noah's ark too. If we don't see these repitles today that means a number of reasonble things anywhere from they failed to adapt to their environment to they were all finally hunted to extinction by humans; perhaps by knights and other similar men seeking to prove their manhood by one of the most primordially fearsome creatures they knew of.
Too bad, really. Maybe if we had more dragons to slay today we'd spend less attention at killing each other.