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a suborder of fishes of the order Clupeiformes. The fishes are medium-sized or large (the arapaima measures up to 4 m long and weighs 200 kg). They are distinguished from other Clupeiformes by the sculptured ornamentation of their scales and dermal bones. Some members of the suborder have no pelvic fins. The suborder comprises three con-temporary families—Arapaimidae, Osteoglossidae, and Heterotidae (with four genera)—and one extinct family.
The Osteoglossoidei are tropical freshwater fishes, distributed in South America, Africa, Australia, and Southeast Asia (the Indochinese Peninsula and the Malay Archipelago). They demonstrate a concern for their young. For example, one species of the genus Scleropages (Australia) carries its eggs in its mouth; one species of the genus Heterotis (Africa) constructs a nest from plants, deposits its eggs inside, and guards it. The suborder has some commercial value.