Kabutops Crest - Scratch, Slash and Cut are always treated as Steel type, increases power of slashing-type moves by 30%.
Omastar Crest - Same effect as Rocky Helmet and immunity to defense stat reduction.
Aerodactyl Crest - Removes Flying type and halves base speed, increases base defense and special defense by 1.5x. Prevents usage of Fly and Sky Drop in battle.
Glory to gen 1 fossil pokemon!