Trachipteriformes

Trachipteriformes is an order of actinopterygian fishes, commonly known as the ribbonfishes. These are deep-sea fishes characterized by their greatly elongated, laterally compressed bodies and reduced fins. They possess a dorsal fin that runs the entire length of their body, often with an iridescent blue or green coloration, and a small caudal fin. The pectoral fins are also small and located low on the body. Trachipteriformes are notable for their slow, undulating swimming motion.

These fishes are typically found in the mesopelagic and bathypelagic zones of oceans worldwide, from tropical to polar waters. They are solitary and rarely observed, making them one of the lesser-studied fish orders. Their diet is thought to consist of small crustaceans and other zooplankton, which they likely capture using their protrusible jaws.

The order Trachipteriformes currently contains a single family, Trachipteridae, and several genera including Trachipterus, Zu, and Desmodema. Species within this order can reach considerable lengths, with some ribbonfishes exceeding several meters. Despite their size and striking appearance, their deep-sea habitat means they are seldom encountered by humans, and much of their biology and behavior remains unknown. Occasional sightings or strandings are often significant events for marine biologists.