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From bulbapedia:HeartGoldSoulSilverSwarmRoute 3-Mudkipie
It is possible to get the Pokemon Gulpin in Pokemon Platinum version by going to the Great Marsh. Gulpin is a poison type of Pokemon.
Gulpin evolves into Swaloti at level 26 in Pokemon emerald
Gulpin evolves into Swalot at LV.26
Gulpin is #316 in the national pokedex, and it is a Poison type Pokemon.