I noticed that Shadow Bone was learned on A-Marowak the level before Cubone evolves into it...is it possible to relearn it from the move tutor? I caught a shiny Cubone earlier, and I just want to make sure before I evolve it to Marowak.
Yes once you get to the Pokémon center before the Alola League, Alolan Marowak can relearn the move as well as any other future level up move. If you need heart scales, well in Konikoni city where you can buy 2 scales per meal at a restaurant.