page_title: Stomiiformes
section_title: Systematics
hierarchical_section_title: Stomiiformes / Systematics
caption_attribution_description: Gonostoma elongatum
context_page_description: Stomiiformes is an order of deep-sea ray-finned fishes of very diverse morphology. It includes, for example, dragonfishes, lightfishes, loosejaws, marine hatchetfishes and viperfishes. The order contains 4 families with more than 50 genera and at least 410 species. As usual for deep-sea fishes, there are few common names for species of the order, but the Stomiiformes as a whole are often called dragonfishes and allies or simply stomiiforms.
  The scientific name means "Stomias-shaped", from Stomias + the standard fish order suffix "-formes". It ultimately derives from Ancient Greek stóma + Latin forma, the former in reference to the huge mouth opening of these fishes.
context_section_description: The Stomiiformes are often placed in the teleost superorder Stenopterygii, usually together with the Ateleopodiformes (jellynoses), but sometimes on their own. 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. That would probably require splitting two additional monotypic superorders out of the Protacanthopterygii, and thus result in a profusion of very small taxa.
  The Stomiiformes have also been considered close relatives of the Aulopiformes. The latter are otherwise placed in a monotypic superorder "Cyclosquamata" but also appear to be quite close to the Protacanthopterygii indeed. 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.
  The ancestral Stomiiformes probably had thin brownish bodies, rows of egg-shaped photophores adorning the lower body parts, and mouths with numerous teeth. From these, two lineages evolved, probably some time during the Late Cretaceous: Among the modern Stomiiformes, the Gonostomatidae and Phosichthyidae are phenetically very similar, but this is due to their being very plesiomorphic and retaining many traits of the original stomiiforms. Each of the two has characteristic synapomorphies with one of the more advanced stomiiform families – the Sternoptychidae and the Stomiidae, respectively. These two, in turn, are highly autapomorphic, and at a casual glance do not look as if they were as closely related to the other stomiiforms as they actually are.
  Thus, the classification of the suborders and families of the Stomiiformes is:
  Suborder Gonostomatoidei
  Family Gonostomatidae – bristlemouths, anglemouths, "lightfishes" (including Diplophidae)
  Family Sternoptychidae – marine hatchetfishes, bottlelights, constellationfishes, pearlsides
  Suborder Phosichthyoidei
  Family Phosichthyidae – lightfishes
  Family Stomiidae – barbeled dragonfishes, loosejaws, stareaters
caption: Elongated Bristlemouth, Gonostoma elongatum
  (Gonostomatoidei: Gonostomatidae)
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