Diagnosis. Cyclothone can be distinguished in the Gonostomatidae by the absence of adipose fin; dorsal- and anal-fin origins about opposite; 12–15 dorsal-fin rays; 16–21 anal-fin rays; 29–35 vertebrae; maxillary teeth close-set, subequal, increasing in size posteriorly; vomerine teeth present or absent, palatine teeth only in an anterior patch; photophores present or absent, SO and isthmus series always absent; when present, photophores along the body in ventral and lateral series, OP 2, OA 6–10; caudal glands present or absent; anus closer to pelvic-fin than to anal-fin origin, or midway between origin of those fins (Grey, 1964; Mukhacheva, 1964, 1974; Badcock, 1982; Nazarkin, 2015). A total of 13 valid species (Fricke et al., 2022).

Remarks. Nine species of Cyclothone were previously reported in the Brazilian EEZ (Tab. 2). Unfortunately, all collected specimens were severely damaged and could not be identified at the species level (S1).