What if they replaced the Rock typing in Fossil Pokémon for a different type?
◦ Omanyte: Rock/Water → Ground/Water
◦ Kabuto: Rock/Water → Bug/Water
◦ Aerodactyl: Rock/Flying → Flying
◦ Lileep: Rock/Grass → Ground/Grass
◦ Anorith: Rock/Bug → Water/Bug
◦ Cranidos: Rock → Rock
◦ Shieldon: Rock/Steel → Steel
◦ Tirtouga: Rock/Water → Water
◦ Archen: Rock/Flying → Flying
◦ Tyrunt: Rock/Dragon → Dark/Dragon
◦ Amaura: Rock/Ice → Fairy/Ice
Some of them would benefit from less resistant and better STAB. Plus, it makes more sense for some of them (like Tirtouga and Anorith) to be part Rock.