including: Sternoptychidae: Baird, 1971,
Gonostomatidae: Baird, 1973 (part); Witzell, 1973 (part).
by J. Badcock
Small deepwater fishes; body deep (with dorsal blade, abdominal keel and post-abdominal spines) or fusiform (without dorsal blade, postabdominal spines and abdominal keel, the latter sometimes inconspicuous); mouth oblique to vertical. Pseudobranch present; gillrakers well developed; branchiostegal rays 6-10, always 3 on epihyal. Swimbladder well developed, gas-filled, euphysoclistous. Scales deciduous.
Photophores: present, some compound, sharing a common photogenic mass.1 BR photophores 3-6, rarely 7. Isthmus with photophores. Single ORB photophore.
Generally oceanic, some pseudoceanic, some benthopelagic; juveniles and adults at about 200-1,500 m by day, larvae and post-larvae often just below shallow thermocline.
Some are diel vertical migrants, others partial or non-migrants; postlarvae sink during metamorphic period either slowly or rapidly; populations usually stratified by size and depth during day, smaller individuals dwelling shallower (may be seasonal). Feeding on zooplankton. Dioecious; breeding season often latitudinally influenced; post-larval photophore development protracted, sequential, OP3 developing first in some, BR first in others.
Genera 10; in Clofnam area 6.
Recent revisions: Weitzman (1974).
1. Parentheses around photophore numbers denote photophores sharing common photogenic mass.