All of the available in-game fossils can be obtained at the stone shop in Konikoni City for 7000 PD.
You can obtain the Skull and Cover Fossils in Sun, and the Armor and Plume Fossils in Moon. Keep in mind that you can only get one of each fossil. Then, take them to the Fossil Restoration Center on Route 8 to revive them into Cranidos and Tirtouga respectively in Sun, or Shieldon and Archen respectively in Moon. A gift Aerodactyl can also be obtained from an Ace Trainer in the Huntail Building in Seafolk Village
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