Like most other members of the subfamily Cetopsinae, mature males in most species have the distal ends of the first rays of the dorsal and pectoral fins elongated into filaments and a convex (vs. straight) margin to the anal fin. Unlike all other species, in "C. coecutiens", the fin ray filaments are present in both sexes and this species must be differentiated by the anal fin. In "C. oliveirai", the fin ray filaments are much longer than in other species, however there is also no difference between the sexes in either the fin ray filament lengths or the anal fin margin. The presence of these traits in mature males cannot be confirmed in "C. amphiloxa", "C. caiapo", "C. jurubidae", "C. parma", due to the small number of specimens. The one specimen of "C. sarcodes" is probably an immature male based on the form of its genital papilla, though it lacks the fin ray elongations and convex anal fin margin of mature males.