The Marcionites according to history ran an ecclesiastical organization parallel to the Church of Rome for 300 years after which they were absorbed into Manicheism. The Manicheans were the sect that Augustine converted to Rome from and during his day they had a large community in Rome with which he was in contact trying to bring them also into the Church of Rome.
“”Marcion derived and developed his heresies from Cerdo who got his through a series of heretics ultimately traceable to Simon Magus.””
Marcion was a nutcase and Simon Magus was a bigger nutcase as Blessed Irenaues points out...
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Now this Simon of Samaria(Simon Magus), from whom all sorts of heresies derive their origin, formed his sect out of the following materials:— Having redeemed from slavery at Tyre, a city of Phœnicia, a certain woman named Helena, he was in the habit of carrying her about with him, declaring that this woman was the first conception of his mind, the mother of all, by whom, in the beginning, he conceived in his mind [the thought] of forming angels and archangels. For this Ennœa leaping forth from him, and comprehending the will of her father, descended to the lower regions [of space], and generated angels and powers, by whom also he declared this world was formed. But after she had produced them, she was detained by them through motives ofjealousy, because they were unwilling to be looked upon as the progeny of any other being. As to himself, they had no knowledge of him whatever; but his Ennœa was detained by those powers and angels who had been produced by her. She suffered all kinds of contumely from them, so that she could not return upwards to her father, but was even shut up in a human body, and for ages passed in succession from one female body to another, as from vessel to vessel.-Against Heresies (Book I, Chapter 23)Doctrines and practices of Simon Magus and Menander
http://www.newadvent.org/fathers/0103123.htm