Amiiformes

Amiiformes is an order of ray-finned fish that includes the bowfin (Amia calva) and its extinct relatives. It is the only surviving order within the Halecomorphi, a group that was much more diverse during the Mesozoic era. Amiiformes are characterized by a number of unique features, including a long dorsal fin, a rounded caudal fin, and a bony gular plate between the lower jaws.

Historically, Amiiformes were a widespread group found in both freshwater and marine environments. Today, however, the bowfin is the only remaining species, confined to freshwater habitats in eastern North America. Fossil evidence suggests that Amiiformes originated in the Late Jurassic period and diversified throughout the Cretaceous and Paleogene periods.

Amiiformes exhibit a mosaic of primitive and advanced characteristics. While they possess a swim bladder that can be used for respiration, they also have a heterocercal tail, a feature more common in more primitive fish. They are predatory fish, feeding on a variety of aquatic organisms, including fish, crustaceans, and insects.

The classification of Amiiformes has been subject to debate, with some researchers placing them closer to teleosts (modern bony fishes) and others suggesting a more basal position within the ray-finned fish lineage. However, molecular and morphological data generally support their placement within the Halecomorphi, as the sister group to Teleostei. Their evolutionary history provides valuable insights into the diversification of ray-finned fishes.