Let's talk about "dragon" lizards.

[Inclusa]

It seems apparent that mythical and fantastic dragons are somewhat based on real life lizards or crocodilians.
The dragon lizards are nothing mythical or fantastic, though.
A good example is the bearded dragon.
It may sound more likely that crocodilians are the base of certain dragons.

[tnjrp]

I take it you want to discuss about the origin of the dragon myths?

There are two popular explanations, one being specifically that real large reptiles such a the Nile Crocodile or the Megalania inspired them, the other (and perhaps even more poplular) being that fossilized remains of megafauna has caused various stories of gigantic animals and even humanoids to start circulating in the human population.

The third, more controversial explanation is that dragon is an atavism, an instinct left over from evolution of primates to fear certain kinds of animals such as raptor birds and lizards; their features would be combined into dragons and other fantastic monsters in the subconscious. The problem with this last is (1) that while it explains the myth, it is fairly unfalsifiable, (2) there is no complete consensus that the fear of certain types of animals is instinctive and (3) the term instinctive is not quite conclusively defined.

[Inclusa]

Thank you for all these info! The legendary dragons seem fairly universal, and we somehow call certain lizards "dragons".

[tnjrp]

I suppose those lizards have struck those who coined their names as particularly dragonlike. Similarly fancifully named are the Gila monster (Heloderma suspectum) and the Thorny Devil (Moloch horridus), for example. I doubt those naming these animals really assumed the Draco genus lizards to breathe fire and hoard treasure etc.

On the other hand some animals such as Salamanders were once quite widely really thought to be the same as the mythical salamanders (that have become to be recarded as fire-elementals in the latter occultism). So local folklore very likely had something otherwordly to say about, say, the Thorny Devil as well.

[Delvo]

Lizards with the word "dragon" in their modern English names didn't inspire dragon myths. It's the other way around; the lizards are named after mythical dragons. Presumably the idea of dragons, at least in Europe, could have been influenced to one extent or another by lizards, but that would be any lizard, not just the ones with "dragon" in their modern English names.

There are older myths than our modern concept of dragons, some of which have some of the same traits, but the complete set is new and unique; the preceding mythical critters always have some differences. Leviathan breathed fire and had skin covered in armor plates/scales and seems to have been very large, like what most people now think of as dragons, but, unlike them, was wingless and associated with the sea. Its fire-breathing ability wasn't added to European dragons until rather recently, and even before that, European dragons didn't necessarily always have wings or such a long neck, and often were given a size that isn't even very large. (Search for images of "Saint George" and you'll find him pointing his spear down more often than up, to slay what appears to be just a crocodile, possibly with slightly lengthened & more-flexible legs & neck and/or a different color.)

The root "drakon" was first used in ancient Greek to indicate either a creature with a deadly stare, which is an ability they had lost by the time the Romans started using the word, or possibly a creature with shiny iridescent scales. (The Indo-European root it came from had something to do with eyesight, seeing, and being seen.) It was used for a creature physically shaped like a snake. In Greek mythology at the time there was no giant lizard/crocodile monster, only some variations on giant or otherwise supernatural snakes or characters associated with snakes, such as Python and Medusa (the latter of which also had the ability to cause death on sight). Similarly, in Old English and other Germanic languages before the importing of "dragon" less than a thousand years ago, the only giant reptile-like monsters were giant snakes, referred to by those languages' words for snakes, such as "wyrm". That makes sense because crocodiles were long gone from Europe by then and, of the remaining reptiles, snakes were larger and more dangerous and alien-seeming than lizards.

The closest creature I can think of to modern dragons back then was a different critter from the "drakon": the basilisk, one of the various ancient Greek combination-critters, like chimeras, Pegasus, and griffins, but in this case combining the traits of a serpent and a bird: a serpent with feathers and wings, and sometimes a bird's two legs and claws. Basilisks were deadly, but depended on extreme venom, the death-stare (which they apparently had in common with the "drakon"), and in some cases the sound of their shriek; they were never particularly large or strong or armored. They could be killed by weasels, which either were immune to their powers or could just move fast enough to bite a basilisk before the basilisk had enough time to react. But at least they combined the long, snake-like body with wings and long legs, and the way they were said to leave a trail of death all around them, complete with a "scorching" effect of their venom on whatever they poisoned, could be compared to fire-breathing. However, just like the word "drakon", they can be traced back a few thousand years, during most of which the two ideas were both around and remained quite separate: one small & weak but with legs, wings, and nasty powers, and one big and strong but wingless, often legless, and lacking weird powers (they even lost the death-stare they'd originally had, as if to keep the two species as distinct as possible). Dragons didn't get their basilisk-like traits until recently, which makes it appear that they got them independently, rather than from combination with basilisks, because if that transfer were going to have happened, it could have long before.