Pokemon Go is introducing some special Pokemon from the tropical Alola region for the first time, and Kanto region Pokemon will start to appear in their Alolan forms in the coming weeks.
I’m pretty sure not everyone knows what an Alola form is, so thanks to bulbapedia, we have the right answer.
“In the Alola region, a species’ regional variant is referred to as its Alola Form. A Pokémon in its Alola Form is described as Alolan — for example, Exeggutor in its Alola Form is referred to as Alolan Exeggutor. Only Pokémon introduced in Generation I have Alola Forms.
In Alola, when breeding Pokémon whose offspring has a regional variant, the offspring’s form depends on its parents. If either parent is the species’ normal form and holds an Everstone, and if the offspring is in the same family as that parent, then the offspring will hatch as the normal form. In all other cases, the offspring will always hatch in its Alola Form.”
There’s only 18 in total, 10 if we count as a family as 1. Most of them are alternate forms of an entire alpine – Geodude family, Meowth family, Rattata family, Vulpix family, Sandshrew family and Grimer family. Only three are special case evolutions of existing Pokemon – Raichu, Marowak and Exeggutor.
It looks like Niantic is leapfrogging Gen 4-6 to go straight to Alolan Pokemon.
See more details about Alolan forms here.