There are five primitive fish families in the state of Iowa. They are described as "primitive" because they lack one or several of the features that are characteristic of the more "advanced" fish species, such as jaws, ganoid scale type, lack of vertebre, body structure, or phylogenetic relations.

The sturgeon and lamprey families each have three representatives in the state of Iowa. Two species of gar can be found in Iowa waters, while the bowfin and paddlefish families each have only a lone member present in the state.