Question

I just want to fill my pokedex all the way and get as much Pokemon as possible.

Comments

Can you explain this?

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Yes, what is extracting?

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Aha! Thank you tags!

Answer 1

You will find the Pokemon you can extract from fossils and other info in the link below.
http://bulbapedia.bulbagarden.net/wiki/Fossil

List:
Helix Fossil - Omanyte
Done Fossil - Kabuto
Old Amber - Aerodactyl
Root Fossil - Lileep
Claw Fossil - Anorith
Skull Fossil - Cranidos
Armor Fossil - Shelidon
Cover Fossil - Tirtouga*
Plume Fossil - Archen*

In HeartGold/SoulSilver, these Pokemon can be revived at the Pewter Museum of Science.
*= only obtainable in Generation V. HeartGold is Gen IV, so they cannot be obtained.

Answer 2

Any Pokemon from Gen. IV or lower but you need a DS Lite or the DS to send Pokemon from GameBoy games such as R/S/E.