Animal group?

[Shaprite]

I think there generally reptiles. Like Shiari said, Pterosaur were classed as reptiles and can fly. There are traces of Mammals-like reptiles in history. Some people believe Dragons have mammal-like traits. Such as Four chambered heart, being warm blooded. There have been dinosaur bones found in cold places which mean maybe there were warm-blooded dinosaurs. There have been traces in history that Reptiles ands Birds come from the same branch. Just compare there anatomy. So pretty much Dragons come from all Classes. They are very diverse creatures, but they're generally reptiles. But that's just my opinion.
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[Namhias]

That's pretty specific. There are no living dragons on earth (physically), so there is no way we can know for certain what the anatomy looked like. All we can do is guess.