Elements can give you a big advantage in Fossil Battles. The basics are:
Fire (red) is stronger against Earth (yellow)
Earth (yellow) is stronger against Air (green)
Air (green) is stronger against Water (blue)
Water (blue) is stronger against Fire (red)
Neutral is not stronger than anything, but isn't weakened by anything either.
Each element goes against one another. Neutral does not have a weakness, but it does not have a strength. I prefer not to have a Neutral, because I like to be more powerful against another team. If the team that you're battling has an advantage to the vivosaur in AZ, keep swapping. Not only does swapping prevent negative support effects, it also throws off the enemy's strategy, so swapping is always a good idea as long as you have at least two strong vivosaurs on your team. If you have a vivosaur that has extra powerful blows when attacking, make sure that its opponent is an element that is weaker. That way, when your vivosaur strikes, its blow will be even more powerful.
