Distal parts of the intromittent organ of Phalloptychus januarius. A, the organ as it is normally found; b, unfolded: (a, third anal ray; b, fourth anal ray; c, fifth anal ray); c, third analy ray, 1 view. d, fifth anal ray, enlarged.
This female killifish was for sale at an aquarium shop. Owners don't know the exact species because the animal was donated to the shop by a hobbyist. I cannot find in the whole Internet any Aplocheilus with a blackish longitudinal band in the flank...