Amiiform fishes were widespread and diverse through the Mesozoic and early Cenozoic, known from deposits across North America, Europe and Asia. That diversity narrowed until one species remained. The bowfin retains features that mark the lineage: a bony gular plate beneath the lower jaw, thin cycloid scales over a partly ossified skeleton, and a heterocercal-derived tail shape.
Its physiology suits the marginal water it now occupies. The swim bladder is vascularised and functions as a lung, so bowfin gulp air at the surface and persist in warm, stagnant, oxygen-poor swamps where bass and pike cannot. Males build nests in vegetation and guard the fry in a dense dark ball for weeks, an unusual degree of parental care.
The bowfin's position relative to the gars, and therefore to the teleost fishes that make up almost all modern fish diversity, has been repeatedly revised as genomic data accumulate, and the branching order is still refined by new analyses.