Atheriniformes is an order of ray-finned fish that includes the silversides and several less-familiar families, including the unusual Phallostethidae.

Members of the order usually have two dorsal fins, the first with flexible spines, and an anal fin with one spine at the front. The lateral line is typically weak or absent. Atheriniform larvae share several characteristics; the gut is unusually short, there is a single row of melanophorees along the back, and the fin rays do not become evident until some time after hatching.

Classification of the atheriniforms is uncertain, with the best evidence for monophyly in the larval characteristics mentioned above.

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