Board Thread:Lore Discussion/@comment-2165692-20161018043733/@comment-26893431-20161023125636

Nelthro wrote: It is not Impossible at all, what year either was seen is completely irrelevant because dragons can live eternally. Paarthurnax is proof of that. Yes it is relevant.

If Nahfalaar was last seen many years ago, and Nafalilargus was last seen after that. It means that it's impossible for them to be the same.