The easy options are:
1) On another planet
2) IN *SPACE*
3) In a lab currently being generated
4) On the island of Komodo (or in a Floridian swamp)
Putting a story in space or on another planet allows for nearly unlimited creativity. Mainly because no one can prove that there are not dragons in *SPACE*. The new or artificial species angle is fun but limited. There can be little history because of the technological limitations however. Redefining the currently held cultural conception can be fun too. A gator can easily get fifteen feet long and is full of teeth from a nightmare. No one can tell this author that the internet named "American Murder Log" isn't a dragon.