The Skull Fossil (Japanese: ずがいのカセキSkull Fossil) is a Fossil introduced in Generation IV that can be regenerated into Cranidos. It is the counterpart of the Armor Fossil.
The Skull Fossil was introduced as a Trainer card in the Pokémon Trading Card Game in the Mysterious Treasures expansion, first released in the Japanese Secret of the Lakes expansion. It is a Fossil Trainer card, so after being played it is put on the Bench as a Colorless-typeBasic Pokémon. It has a Poké-Body that says if it is Knocked Out by damage from an opponent's attack, Skull Fossil's owner gets to flip coins until they get tails and put one damage counter on the Attacking Pokémon for each heads. It can evolve into Cranidos that evolve from a Skull Fossil.
Skull Fossils are also featured on Unidentified Fossil cards, which are Fossil Trainer cards that can evolve into Cranidos as well.