Complex sentence: The reason for this was that it brought together, on one stage, the four greatest ballerinas of the time--in order of appearance, Lucile Grahn, Carlotta Grisi, Fanny Cerrito, and Marie Taglioni.
Split into simpler sentences: The reason for this was that it brought together, on one stage, the four greatest ballerinas of the time. The ballerinas were, in order of appearance, Lucile Grahn, Carlotta Grisi, Fanny Cerrito, and Marie Taglioni.