You can't
whomever just said you cant is a liar...i found one by smashing a rock in the city where you find the unknown pokemon...but my bf smashed the same rock and got something different so i dont know...but its not impossible
use rock smash on rocks and you will find it eventualy
go to a cave
u cant get the dome fossil in heart gold only in soul silver
the dome fossil is one, I just found it !in soul silver you can get the old amber (aerodactyl) and dome fossil (kabuto) you can get them at the Ruins of Alph by smashing rocks and you can revived them at pewter city musseum...
just keep on smasing rocks.
Kabuto
You must evolve Kabuto, which comes from the Dome Fossil.
On cinnabar island it can be turned into a Pokemon
You buy it with points at the Pokeathlon Dome.
the fossil person is behind the desk in the pewter museum
You have to trade it from HeartGold, in the ruins of alph when you use rock smash on the rocks you can find the Dome Fossil(for kabuto) but that's only for SoulSilver, the Helix Fossil(for Omannyte) is only found in HeartGold
At the Pokethlon Dome or at the Bug Catching Contest
walk out and in again and ta-da! you have a Pokemon extracktid from a fossil