In fantasy, dragons have either four legs or two legs. This has been debated to be the difference between a traditional dragon and a wyvern. Personally, I like dragons who have two legs and two wings because it seems more physically plausible. There has never been a vertebrate in the fossil record that has six limbs so a dragon with two legs and two wings has more realism to it. Therefore, the dragons in my fantasy series will have two legs and two wings as well just to keep with the realism of the story.