Dragons are the most interesting animal that never existed. No other mythological creature has had such far reach across cultures and centuries nor so much lore behind it. They’re even mentioned in the Bible, albeit as a symbolic representation.
But despite being so universal, they are also diverse. Although many cultures have dragons in their mythology, their designs vary widely, and some of that might have to do with translation issues. They are often lizard- or snake-like, can often fly, sport spines and horns, and have magical attacks like breathing fire. Many don’t follow these patterns, though. Even so, most dragons of legend fit into one of several categories.
The most common classification. People also know them as western dragons, because they mirror the designs in medieval Europe. They have four legs (some can stand up on the hind ones, others walk on all fours), a pair of bat wings for flying, and can breathe fire. Scales cover their bodies, like lizards.
Summary: 4 legs, 2 wings
This is where things get controversial. Almost every recent film featuring dragons has what would more technically be called the wyvern design, or at least the updated version of wyverns. Originally, wyverns were smaller, didn’t breathe fire, and had a poisonous spine on their tails, like scorpions. Design-wise, their biggest difference was that they had no forearms, only two hind legs and two wings, which they used to walk on when grounded. Now, think back to every major dragon depicted in film in the last decade or two. Harry Potter dragons, Reign of Fire dragons, and Smaug in The Hobbit (despite Tolkien himself drawing him with four legs), plus the dragons in Game of Thrones and Skyrim, they all followed this design, even though people called them dragons. The only exception I can think of is How to Train Your Dragon, an animated film.
There are a few reasons for this. One is a sense of realism: excepting insects, there are no hexapods (animals with six limbs) that we know of. Bats, birds, and even pterodactyls all follow this design of the forearms being wings. Here is another reason.
Personally, I dislike this trend. They seem less intelligent and more animalistic this way, in my opinion, and less true to their source material. Plus, it creates confusion, especially in the cinematic Lord of the Rings universe: if Smaug the dragon has only two legs, then what were the creatures the Naz’gul rode in the original trilogy? Smaller dragons? The wyverns might be more realistic, but come on, they’re dragons. The number of legs isn’t going to change the fact that they’re too big to fly, or even exist, and they wouldn’t be able to breathe fire. It seems silly to worry about them being hexapods without addressing that issue.
Summary: 2 legs, 2 wings
I’m going to lump several types of dragons in this category. This includes eastern dragons, associated with China and nearby areas. They are either serpentine with no legs or long with two to four legs. They don’t have wings, but can often fly using magic. These dragons are such a part of their cultures that they’re the only mythological beings in the Chinese zodiac. They are often more benevolent than the fire breathing dragons of the west.
Summary: 0-4 legs, no wings
Summary: 4 legs, 0 wings
There are some other versions and classifications, but there’s no need to go more specific. Some differences between dragons include what type of breath they have, whether they have scales or feathers, what colors they are, and many other things.
Just for fun, here are some famous dragons to grace myth, book, and screen.
Smaug is the most famous dragon in LotR, although not the biggest. He is the enemy in The Hobbit who treasures his hoard of gold and dies from a well placed arrow by a character who comes out of nowhere. In the movies, Bard has a little more characterization and pulls a reverse William Tell, shooting a dragon using the head of his son. He is a dragon in the book, wyvern in the movies.
This dragon became famous for growing so big it wrapped around the world and bit its tail. When it lets go, Ragnarok will begin. Sounds like a wyrm.
He has spikes, breathes fire, and kidnaps princesses, so he’s a dragon. Or a turtle. No, dragon sounds cooler. I’d classify him as a drake.
Slifer the Sky Dragon
And if you want to see more on the science of dragons, look at this video.