Fossils, phrasally referred to as Pokémon Fossils, are physiological vestiges of prehistoric Pokémon that can be biogenerated into fossilized Pokémon.
Fossilized Pokémon tend to be scarcer than more organic Pokémon, as they are only originatively obtainable by obtaining a Fossil—a rarity in its own right—and reanimated into the living version of the Pokémon.
They are most commonly obtained by unearthing them; the two systems available for doing so are diggable patches and Excavation Sites. Additionally, all-five available fossils are subsumed under Brock's prizeset.
Reaniamting Fossils
Fossils can be reanimated by turning them in to bioscentists; one cadre of them is stationed in each region, as explained below.
They can be reanimated in Cinnabar Island's lab in room 4 of the lab; this also requires that you have defeated Blaine in Cinnabar Gym, first, since the room will be inaccessible before then.
They can be reanimated in the Ruins of Alph research center.
Upon completing the Devon Corp quest, one of the employees in the eponymous building will offer to reanimate any five of the available fossils.
Available Fossils
 | Helix Fossil |
| Reanimates into → | |
|
 | Dome Fossil |
| Reanimates into → | |
|
 | Old Amber |
| Reanimates into → | |
|
 | Root Fossil |
| Reanimates into → | |
|
 | Claw Fossil |
| Reanimates into → | |
|
Other usages
They can also be donated to Pewter Museum; after doing so, you will see the Fossil visibly on the pedestal north of the Curator.
After donating three discrete Fossils, you will have access to the Ancient Power-tutor in Ruins of Alph research center for 
3,500 per tutee.
3,500 per tutee.