How do I get a skeleton dog?
Solution 1:
There are no skeleton dogs in vanilla (unmodded) Minecraft.
To get skeleton dogs alongside regular dogs, you will need a mod, that will add such a new mob (or variation).
If you don't need normal dogs, you may just use a resource pack that will replace normal dog's texture with skeleton. The dogs will still behave as usual, but look different.
I'm not able to recommend any specific mods or resource packs now, though.