Marine Smelts and allies: Order Argentiniformes

There are about 200 species of fishes in the order Argentiniformes. For the most part, they are fish of the deep sea, often either silvery or black. As a keen observer you'd notice a few key characteristics that make them distinct. First, they usually have an adipose fin (the fin behind the dorsal fin). They have a physoclistous gas bladder (an organ full of air and differentiated from other gas bladders because it is completely seperated from the gut). Additionally, they almost always lack teeth.

Until recently, all of the fish in this order were placed in the order Osmeriformes, with the other smelts. Yet, as scientists learned more about this group, certain ones decided it waranted its own order. The most recent edition of Fishes of the World (Nelson 2006) noted it as a distinct order in the Superoder Protacanthopterygii. Because of that, there is still little documentation for this group on the web.

Taxonomy

Family Argentinidae (23 species)

This family includes the argentines or herring smelts. There are only two genera: Argentina and Glossanodon.

Family Ophisthoproctidae (11 species)

There are six genera of deep sea fish known commonly as the barreleyes or spookfishes: Bathylychnops, Dolichopterx, Macropinna, Opisthoproctus, Rhynochohyalus, and Winteria.

Family Microstomatinae (~38 species)

This family is known as the pencil smelts. There are about 49 or 50 genera, and thus too many to list individually here.

Family Platytroctidae (37 species)

This family is known as the tubeshoulders because of a black shoulder sac apparatus that is located just above the pectoral fins. It produces a blue-green luminous fluid for producing light at depth. There are 13 genera: Barbantus, Holtbyrnia, Maulisia, mirorictus, Normichthys, Paraholtbyrnia, Pellisolus, Persparsia, Platytroctes, Sagamichthys, Searsia, Searsioides, and Tragularius.