While this evolution retains Flygon's dual Ground/Dragon attributes, it provides the Pokemon with new armor-like pieces ... in Pokemon that can Mega Evolve. Charizard and Mewtwo, the latter ...

Though the main games span 48 Mega Evolutions (including the two Charizard and Mewtwo each have access to each) on the feature's debut in Pokémon Go, not all have been released into Pokémon Go.