ABSTRACT
This order contains the largest number of vertebrate animals on earth although they are small to medium sized fishes found in all oceans from the surface (as young) to mesoand bathypelagic zones. Based on larval abundances, the species of the genera Vinciguerria and Cyclothone are the most abundant by numbers of any vertebrate. The order contains about 51 genera and about 321 species, but family names are in a state of flux because of the lack of a satisfactory classification (Nelson 1994). Until the situation is satisfactorily resolved, herein I consider those familial taxa which best recognize differences for use in identifying young stages. The primitive stomiiforms comprise the abundant taxa (Families Gonostomatidae, Sternoptychidae, Phosichthyidae) while the advanced groups (Chauliodontidae, Stomiidae, Astronesthidae, Melanostomiidae, Malacosteidae, and Idiacanthidae) comprise species that are rare in collections. This rarity is in part responsible for our limited knowledge of the order. Ahlstrom, Richards & Weitzman (1984) reviewed the primitive families and provided much information of ELH stages and Kawaguchi & Moser (1984) did likewise for the advanced groups. Traditionally, the order was classified with two primitive families (Gonostomatidae and Sternoptychidae) and five advanced (those listed above). The primitive genera were rearranged into three families and Fink (1984, 1985) combined the 26 genera of the advanced group into one family-Stomiidae, which is a sound systematic conclusion. His characters included presence of a single infraorbital bone, lack of gill rakers in adults, presence of a mental barbel associated with the hyoid apparatus, a portion of the adductor mandibulae muscle inserting on the postorbital photophore, and a divided geniohyoideus muscle. Subsequent to Fink (1984, 1985), Harold & Weitzman (1996) discussed the changes in classifications and concluded that, though still incomplete, the Phosichthyidae and the advanced stomiiform genera are not diagnosable. Until this is resolved I follow Moser & Watson (1996) who, in turn, followed Eschmeyer (1990) in continuing to retain the advanced genera in six families, as this aids in ELH identification.
