Most recent Cassini observations by the Imaging Science Subsystem (ISS) showed that the third largest Saturnian satellite, Iapetus, has a curious ridge system exactly aligned with its equator . Because Iapetus has a large Hill sphere for the trapping of circum-satellitary material, a ring system might have been present during its formation. A scenario is proposed to describe how the equatorial ridge system could have been produced by the collisional accretion of a ring remnant subsequent to the formation of the proto-Iapetus.