Argentiniformes

The Argentiniformes /ɑːrdʒənˈtɪnɪfɔːrmiːz/ is an order of marine ray-finned fish whose distinctness was recognized only fairly recently. In former times, they were included in the Osmeriformes (typical smelt and allies) as suborder Argentinoidei. That term refers only to the suborder of marine smelts and barreleyes in the classification used here, with the slickheads and allies being the Alepocephaloidei. These suborders were treated as superfamilies Argentinoidea and Alepocephaloidea, respectively, when the present group was still included in the Osmeriformes.

They contain six or seven families with almost 60 genera and at least 228 species. A common name for the group is marine smelts and allies, but this is rather misleading since the "freshwater" smelts of the Osmeridae also live predominantly in the ocean.

The earliest fossil argentiniform remains are otoliths of indeterminate argentinids from the Barremian Kimigahama Formation of Japan. Later otoliths are known of other indeterminate taxa and Argentina itself from the Late Cretaceous (Maastrichtian) of the United States and Germany. A fossil family that might belong in this order are the Pattersonellidae, but more recent studies have found them to be basal euteleosts.