Old Amber

The Old Amber is a fossil from which Aerodactyl is resurrected from.

https://vignette.wikia.nocookie.net/pokemon/images/2/20/Mine_Old_Amber_1.png/revision/latest?cb=20110524005505

Ways to obtain

 * Use Rock Smash in the Ruins of Alph, as well as a few other select locations. (HeartGold/SoulSilver)
 * Old Amber can be found in the lowest floor of Twist Mountain, as well as many other fossils. (Black/White).
 * Use Rock Smash in Glittering Cave. (Pokémon X and Y)