The Book of Lost Tales
The other dragon Glaurung has many similarities as well. In Tolkien's "The Book of Lost Tales", Glaurung is described as a flightless dragon that hoards gold, breathes poison, and has "Great cunning and wisdom". In Tolkien's book "The Children of Húrin", he is slain by Turin from below much like Fafnir. Turin and Glaurung also have an exchange after the mortal blow is dealt.