is the closest living relative of the Sternoptychidae, and these two form the suborder Gonostomatoidei. Indeed, some Sternoptychidae are called "bristlemouths", like the bulk of the Gonostomatidae. Compared to their relatives, the marine hatchetfishes are a more apomorphic group, but they have evolved in an entirely different direction from the other "advanced" lineage of Stomiiformes, the huge family Stomiidae. Classification Typically, the Sternoptychidae are divided into two subfamilies, with the more plesiomorphic members making up the Maurolicinae. Symplesiomorphies are no reliable indicator of actual relationships, however. While it remains to be seen what Sternoptychidae other than the pearlsides (Maurolicus, the type genus) do actually belong in the Maurolicinae, it is unlikely that the two-subfamily arrangement is correct. It may even be that the Maurolicinae are just an indiscriminate assemblage of unrelated basal Sternoptychidae and are altogether invalid. The Sternoptychinae – the "true" marine hatchetfishes – on the other hand are monophyletic. The provisional arrangement of subfamilies and genera of Sternoptychidae is as follows: Subfamily Maurolicinae Genus Araiophos (2 species) Genus Argyripnus – bristle-mouth fishes (6 species) Genus Danaphos – bottlelights (1-2 species) Genus Maurolicus – pearlsides (15 species) Genus Sonoda (2 species) Genus Thorophos (2 species) Genus Valenciennellus – constellationfishes (2 species) Subfamily Sternoptychinae – marine hatchetfishes, deep-sea hatchetfishes Genus Argyropelecus – silver hatchetfishes (7 species) Genus Polyipnus (32 species) Genus Sternoptyx (4 species) Footnotes References (2008): On the cephalic and pectoral girdle muscles of the deep sea fish Alepocephalus rostratus, with comments on the functional morphology and phylogenetic relationships of the Alepocephaloidei (Teleostei). Anim. Biol. 58(1): 23-29. (2005): Order Stomiiformes. Version of 2005-FEB-15. Retrieved 2009-SEP-28. (2006): Family Sternoptychidae. Version of 2006-OCT-10. Retrieved 2009-OCT-02. (1998): Sternoptychidae. In: : Encyclopedia of Fishes: 121. Academic Press, San Diego. (1968-1982): Oxford Latin Dictionary (1st ed.). Oxford University Press, Oxford. (2006): Fishes of the World (4th ed.). John Wiley & Sons, Inc. (1910): English-Greek Dictionary - A Vocabulary of the Attic Language. George Routledge & Sons Ltd., Broadway House, Ludgate Hill, E.C. Searchable JPEG fulltext External links http://www.seasky.org/deep-sea/hatchetfish.html Ray-finned fish families