Not75Drops
Member
I have this theory that the "rock" type in fossil Pokemon is a side effect of resurrecting them.
Like Aerodactyl in ancient times was Flying/Dragon, but when he was rebord, he lost his Dragon type and it was replaced with Rock as a side effect of the process.
Aerodactyl - Dragon/Flying
Kabuto - Bug/Water
Omanyte - Water
Lileep - Grass/Water
Anorith - Bug/Water
Cranidos - Normal
Sheildon - Steel
Tirtouga - Water
Archen - Normal/Flying
Tyrunt - Dragon
Amaura - Ice/Fairy
It's heavily implied on the official site for XY that Mega Aerodactyl was what it was like before it became extinct.
http://www.pokemonxy.com/en-us/pokemon/mega_pokemon/
http://www.pokemon.co.jp/ex/xy/pokemon/mega/19.html Japanese site as well so it wasn't something that the US site made up.