sentences:  However, astronomers fell into the habit of referring to them using Roman numerals, with Iapetus being Saturn V. Once Mimas and Enceladus were discovered in 1789, the numbering scheme was extended and Iapetus became Saturn VII.And with the discovery of Hyperion in 1848, Iapetus became "Saturn VIII", which it is still known by today (see naming of moons).Geological features on Iapetus are named after characters and places from the French epic poem "The Song of Roland".