I've been wondering. Legends are usually based on fact, right? I believe our "dragon! " stories come from dinosaurs - if you don't belive that they were around when people were, get a Bible and read the part in Job about the Leviathan. Or the accounts of the 14th century French town that killed a "dragon", one that looked just like a Triceratops.
So in the WoT, were did the Dragons come from? In the special prolouge for TEotW, Tam al'Thor says, in response to Perrin's question:

"Perrin scratched at his head. "Master al'Thor," he said slowly, "what does 'the Dragon' mean? If somebody's called the Lion, it means he's supposed to be like a lion. But what's a dragon?" Egwene stared at him. She had never thought of that. Maybe Perrin was not as slow as he appeared." "I don't know," Rand's father answered simply. "I don't think anyone does. Maybe not even the Aes Sedai." He let the sheep go that he had been shearing, and motioned for another to be brought. Egwene realized that he had been done with it for some time. He must not have wanted to interrupt his story. Master Cole opened his eyes and grinned. "The Dragon. It surely sounds fierce, though, now doesn't it?" he said before letting his eyes drift shut again.

There has to be something to base this on, and I think Dragons still live - real live deadly ones. Either under the sea or in Shara's neighboring continent.