Each creature card in your graveyard has the chosen creature type in addition to its other types.
If Spirit is the chosen creature type, the soulshift ability will be able to target any creature card in your graveyard of the appropriate mana value. Suppose two creatures, including one with soulshift, are put into your graveyard from the battlefield at the same time. The Spirit creature type is added as the cards enter the graveyard, just before you choose the target for the soulshift ability.
