[quote=@j8cob]
But...

[hider=Spoilers]
All the Dragons in FT were half-dead and unable to reproduce by the start of the story.
[/hider]
[/quote]

Well I know about that, but there are still options. Some one else utilized time magic of some sort, or other forms. An artificially created dragon? Fairy tail tech and magic can do wonderous things. 

[quote=@Caits]
A fossilized egg! That came alive and hatched afterwards!
[/quote]

Or something like that, and the egg or eggs, were brought back using magic and a machine or something like the fossil pokemon in pokemon. .__.

I have put thought into this...