[1] The scientific name means "Stomias-shaped", from Stomias (the type genus) + the standard fish order suffix "-formes".

The largest species is the barbeled dragonfish Opostomias micripnus, widely found in the Atlantic, Indian and Pacific Oceans and measuring about 50 cm (20 in) in adult length.

The coloration is typically dark brown or black; a few (mostly Gonostomatoidei) are silver, and photophores (light-producing organs) are common in this order.

The lighting mechanism can be very simple – consisting of small gleaming points on the fish body – or very elaborate, involving lenses and refractors.

The light produced in these glandular organs is the product of an enzymatic reaction, a catylization of coelenterazine by calcium ions.

When the sun sets, most of them follow the dimming sunlight up to near-surface waters, which are richer in animal life such as small fishes and planktonic invertebrates.

During the night, these Stomiiformes hunt and feed on such organisms, swimming back to deeper waters when the sun rises.

[citation needed] Like many benthic fish species, certain members of the order – especially in the genera Cyclothone and Gonostoma – change their sex during their life.

Whether it is indeed justified to accept such a small group is doubtful; it may well be that the closest living relatives of the "Stenopterygii" are found among the superorder Protacanthopterygii, and that the former would need to be merged in the latter.

In some classifications, the "Stenopterygii" are kept separate but included with the Protacanthopterygii and the monotypic superorder Cyclosquamata in an unranked clade called Euteleostei.

The relationships of these – and the Lampriformes or Myctophiformes, which are also usually treated as monotypic superorders – to the taxa mentioned before is still not well resolved at all, and regardless whether one calls them Protacanthopterygii sensu lato or Euteleostei, the phylogeny of this group of moderately-advanced Teleostei is in need of further study.