Fossils in Pokémon Red: Omanyte, Kabuto and Aerodactyl

Pokémon Red has three fossils. In Mt. Moon you choose the Helix Fossil (Omanyte) or the Dome Fossil (Kabuto); the Old Amber (Aerodactyl) is behind the Pewter Museum. The Cinnabar Lab revives each at level 30.

Omanyte: Helix Fossil from Mt. Moon B2F.
Kabuto: Dome Fossil from Mt. Moon B2F (you only get one of the two).
Aerodactyl: Old Amber from a scientist at the back of the Pewter Museum (enter from the side door, reached with Cut).

Take the fossil to the scientist in the Cinnabar Lab fossil room, leave, and come back: your Pokémon is ready at level 30.

Frequently asked questions

Should I pick the Helix or Dome Fossil?

Both are Rock/Water. Omanyte (Omastar) has better Special; Kabuto (Kabutops) has better Attack and Speed.

Where is the Old Amber in Pokémon Red?

At the back of the Pewter Museum, through the side entrance.