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Body elongate; mouth large; premaxillary teeth even; teeth on posterior half of upper jaw strongly curved forwards, enlarging uniformly caudad without small intermediate teeth; vomer with teeth. Pseudobranch absent. Gillrakers on first arch 23–25, 5 (6) on hypobranchial, no raker in articulation of epi- and ceratobranchial; branchiostegal rays 13–14, 5–6 on epihyal. Dorsal-fin rays (13) 14; pectoral-fin rays (8) 9–10; pelvic-fin rays (5) 6; anal-fin rays 18–20; dorsal- and anal-fin origins about opposite; last dorsal- and anal-fin rays not split to base; dorsal adipose fin absent; anus midway between pelvic bases and anal fin origin or slightly nearer former. Pyloric caeca 3. Vertebrae 30–52. Scales present.
Photophores SO absent, ORB 1, OP 2, BR 9–10, IV 3 + 10 (11); VAV 4–5, 2–3 anterior to genital opening; AC 14–16, two between last anal and first procurrent rays; OA 9; supra-caudal gland massive, extending to dorsal base, larger than infracaudal; opercular gland weakly developed, restricted to area between OP. Color of uniformly brown.
Cceanic, deep mesopelagic; pre-metamorphic post-larvae at 0–70 m, juveniles and adults at 300 1,200 m; usually vertically orientated in daytime (submersible observations).
Badcock J. 1984. Gonostomatidae. pp. 284–301. In: P.J.P. Whitehead MLB, J.-C. Hureau, J. Nielsen, and E. Tortonese editor. Fishes of the Northeastern Atlantic and the Mediterranean. Paris: Unesco. p 1473 pp.
The following is a general description of the morphology of species of the genus Cyclothone from Badcock (1984).
Species of the genus typically small, fairly elongate. Pseudobranch absent; gill filaments longer in males; branchiostegal rays 13–14 (5–6 on epihyal). Dorsal- and anal-fin origins about opposite; last dorsal- and anal-fin rays not split to base; dorsal adipose fin absent; anus closer to pelvi-fin base than to anal-fin origin or a midpoint. Swimbladder regressed in adults. Scales present or absent.
Presumed hermaphroditic.
Males to 36 mm, females to 60 mm SL.
Circumglobal in tropical and subtropical oceanic waters.
Consumes mainly copepods.
Off Galápagos Islands, eastern Pacific, 0°36'S, 78°138'W, depth 0–2413 fathoms.
Syntypes: MCZ 28515, 35152; USNM 120400 [ex MCZ 28515].
