Eles ganham o subtipo, mas não seus recursos
Das regras em Eidolons desencadeadas :
The first time a summoner calls his eidolon, he must decide on its subtype. The eidolon's subtype determines a number of its base statistics and abilities, as well as its overall look and theme. The subtype also determines what sort of evolutions the summoner can select for his eidolon using the evolution pool. Once the choice of subtype is made, it cannot be changed.
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Name: This is the name of the eidolon's subtype. The eidolon gains this as a subtype, but unless otherwise noted, it does not gain any of the features, abilities, or weaknesses of that subtype.
(ênfase minha) Note que a maior parte das evoluções da base conferem ao Eidolon as características de seu subtipo. Por exemplo, um Eidolon Elemental ganha imunidade ao flanqueamento no 12º nível e imunidade a acertos críticos e dano de precisão no 16º.