In today's latest video update, which was included in today's Nintendo Direct, some new information was brought to light.
Rattata has a Dark/Normal Alola form.
Some Pokémon have a unique Z-Move. Alolan Raichu has Stoked Sparksurfer, and Snorlax has Pulverizing Pancake. These Z-Moves require unique Z Stones. Snorlax's Snorlium Z can only be obtained as a Munchlax pre-order bonus.