The dragon is one of the most ancient and cross-cultural icons of myth in human history. The Europeans, the Chinese, the Maya, as well as others, all have dragon-like creatures within their mythologies. I am of the opinion that his is due to dinosaur bones popping up out of the earth for the entirety of our time on this rock, but that is beside the point.
The anatomy of these creatures is varied. The slinky, snake-like creature is common in Asia, while in Europe the winged, four clawed variety is the most common, usually with its accompanying fire breath. The Aztecs had feathers on their dragonish gods. This becomes even more interesting in light of the fact that most modern scholars believe that birds are descendants of dinosaurs, and even T-Rex may have had feathers. But again, I digress.
The question that needs to be answered is: which of these potential body types would be most likely to evolve in a “real” fantasy world?
The giant snake would be hard to imagine not crushing its ribs under its own weight as it slithered through the forest or mountains, and, precluding some special magic, they certainly would not fly. The feathers might be pretty, but that takes away some of the classic magic of “dragon scales” and almost makes them become too much like birds.
However, there is a problem with the classic European dragon, four walking limbs and a flimsy pair of leathery wings just pasted onto their spine. This sort of creature would effectively be a six-limbed beast. How many six-limbed, land using vertebrates have evolved in nature? In a world entirely inhabited by four-limbed vertebrates (you know, horses, dogs, birds, bats, frogs, people), how did a six-limbed beast just pop up?
(I have the reverse problem with Avatar, where the Navi have 4 limbs while everything else has 6 — and yet they can all are close on the Pandoran evolutionary scale to share brain chemicals…through their hair? Don’t get me wrong — I liked the movie a lot. OK, digression over.)
That is why I posit that the most accurate form of the dragon is the one most famously used in the Rankin-Bass version of the Hobbit for Smaug or in the movie “Dragonslayer” — a four limbed creature with wings on its forearms. It is more used to the sky than the ground. The wings fold back along those arms, as extensions of the outer digit, allowing for some ability to crawl along the ground or hobble along with its front legs aiding its stubbier rear ones.
It would be more like a Pterodactyl with slightly more prehensile claws then a komodo dragon with an extra set of wings.
Now, the breathing fire — that’s a whole other story.