The Gemara says that, "Amar Rav Nachman Amar Shmuel Mishum Rebbi Shimon ben Elazar," and Tosfos leaves out the words "Mishum Rebbi Shimon ben Elazar," as does the Tosfos ha'Rosh.

We cannot prove from this Hashmatah that they did not have the words "Mishum Rebbi Shimon ben Elazar" in their Girsa of the Gemara, because it is the manner of Tosfos -- when citing the words of the Gemara -- to omit words which are not relevant to his question and his answer. In this particular Dibur, the main question that Tosfos asks is based upon Rav Nachman and Shmuel . who ruled that the Kesuvah is mid'Rabanan, and the Halachah normally follows their views in matters of monetary law (as the Tosfos ha'Rosh says clearly).

Therefore, the fact that Rebbi Shimon ben Elazar also ruled like this is not relevant to the point of Tosfos. Even though he is a Tana, we find a Machlokes Tana'im with regard to this ruling, as the Gemara mentions later, and thus there is no reason to rule, l'Halachah, specifically like Rebbi Shimon ben Elazar.

However, Tosfos in Sanhedrin (8a) also leaves out the words "Mishum Rebbi Shimon ben Elazar" (as well as the words "Amar Shmuel"), and thus perhaps these words were not in the Girsa of the Gemara of Tosfos (in Sefer Shinuy Nuscha'os, there is no other record of any other Girsa in any manuscript that we have), for we find no other place in the Gemara where Shmuel (an Amora in Bavel) quotes a Tana (like Rebbi Shimon ben Elazar).

Mordecai Kornfeld