When you go to relic castle a person will say "Holding these Pokemon Fossils is too much weight. Would you like one?" Then, you have a choice of which one to choose. I have Pokemon black and white, so i got both. The Plume Fossil gives you Archen, and the Cover Fossil gives you Tirtouga. Once you receive your fossil, go to the museum in Nacrene City and talk to the woman on the left.
Chat with our AI personalities
no you cant but i will tell you witch is the strongest it is archen the plume fossil
archen
In the first bit of relic castle talk to the woman she gives you the choice of plume(archen) or cover(tirtouga) fossil
Bring it to Nacrene museum
You have 9 types: Armor Fossil, Claw Fossil, Cover Fossil, Dome Fossil, Helix Fossil, Old Amber, Plume Fossil, Root Fossil, Skull Fossil