Iso is an Indo-Pacific genus of silversides, commonly called surf sardines, the only genus in the monogeneric family Isonidae, they were formerly classified in the family Notocheiridae alongside the surf silverside but they are now thought to be within the suborder Atherinoidei while the surf silverside is classified in the suborder Atherinopsoidei, along with the Neotropical silversides. It contains five species to date, the first of which was described in 1895.

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