This is a general opinion comment. But do you think that dragons existed? We have fossil evidence of large reptiles (dinosaurs) there are some theories that they evolved into birds. Could there have been some giant winged reptile in existence in early human times that survived as legend in so many cultures, and was perhaps hunted to extinction? Sure, there is currently no fossil record of them, but that doesn't mean much as I am sure the majority of species in history have disappeared without leaving any fossil trace. And I don't think we can completely ignore human history and legends as sketchy as they can sometimes be.