Monospecific: Heterotis niloticus
Heterotis niloticus 2 (Cuvier, 1829) this species gives the name to the subfamily whose other member is Arapaima gigas. It has a terminal mouth and long unpaired fins nearly equal in length. It grows up to about 90 cm and is a nest-builder and an air-breather like Arapaima, but lives in Africa instead of South America. Remarkable is the fourth gill arch which is spiral shaped and works as a filter apparatus to concentrate the tiny phytoplankton, its diet, and wrap it into a layer of mucilage before swallowing it.