Sio (genus)

{{Short description|Species of fish}}

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| status = LC | status_system = IUCN3.1

| status_ref = {{cite iucn |author=Moore, J. |year=2019 |title=Sio nordenskjoldii |volume=2019 |page=e.T135432447A135579457 |doi=10.2305/IUCN.UK.2019-2.RLTS.T135432447A135579457.en |access-date=19 January 2024}}

| parent_authority = Moss, 1962

| taxon = Sio nordenskjoldii

| authority = (Lönnberg, 1905)

| synonyms = Melamphaes (Plectromus) nordenskjoldii Lönnberg, 1905

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Sio is a monotypic genus of fish in the family Melamphaidae, the ridgeheads. The only species is Sio nordenskjoldii, or Nordenskjold's bigscale.{{FishBase genus |genus=Sio |month=October |year=2023 }} It has a circumglobal distribution on the southern hemisphere at depths from {{convert|200|to|3000|m|ft}}.