Notacanthiformes

Notacanthiformes is an order of ray-finned fish belonging to the superorder Acanthopterygii. This order is characterized by its unique body shape and the presence of a notochord, a flexible rod that runs along the length of the fish's body, providing support and facilitating movement. The notochord is a remnant of the notochord found in the embryos of vertebrates, and its presence in adult Notacanthiformes is a distinctive feature that sets them apart from other ray-finned fish.

The order Notacanthiformes consists of two families: Notacanthidae and Halosauridae. Notacanthidae includes the genus Notacanthus, which is known for its elongated, eel-like body and the presence of a long, flexible spine on its back. Halosauridae, on the other hand, includes the genus Halosaurus, which is characterized by its short, robust body and the presence of a large, fleshy fin on its back.

Notacanthiformes are found in deep-sea environments, typically at depths of 1,000 to 4,000 meters. They are known for their bioluminescent capabilities, using light to attract prey or communicate with other fish. Their diet primarily consists of small crustaceans and other invertebrates.

The order Notacanthiformes is of particular interest to scientists due to its unique evolutionary history. The presence of a notochord in adult fish is a rare occurrence in the animal kingdom, and the study of Notacanthiformes provides valuable insights into the evolution of vertebrates.