I also support Finno Ugric mythologies as a plural term because there is no just one mythology or system of myths but different and diverse Finno Ugric mythologies Some kind of an analogy for this is how we name the groups of languages we do not speak of common Finno Ugric language but Finno Ugric languages plural Baltic Finnic mythology is still acceptable as a singular term because Baltic Finnic mythologies share very much with each other Kalevala for example is collected from speakers of different baltic Finnic languages But there could not be an opus of Fenno Ugric or Fenno Volgaic mythology it would just be a mess of unrelated material and languages that are not mutually intelligible puhu