smaug

[The Saucepan Man]

Just how old was Smaug anyway? Was he around in the time of Glaurung?

Unlikely. If Morgoth had developed winged Dragons by that stage, I am sure that he would have deployed them. Winged Dragons appeared for the first time during the War of Wrath, when Ancalagon's squadron flew out from Angbad.

It is possible that Smaug was one of those in Ancalagon's squadron who escaped the fall of Angbad. I think it more likely, however, that he is descended from one (or a pairing of) such escapees, since I believe that he is said to have been in his youth when he first attacked Erebor.

Assuming that's right, it is likely that he was the last Dragon of pure descent from the original winged beasts of Ancalagon's horde. I believe that, in one of his Letters, Tolkien indicated that he did not intend that Smaug was the last Dragon, but rather that he was the last of the Great Dragons. Possibly those remaining were the result of inter-breeding between Ancalagon's line and lesser beasts.