In yesterday’s daf, on Nazir 57b, we find:
מָר זוּטְרָא מַתְנֵי לַהּ לְהָא שְׁמַעְתָּא דִּשְׁמוּאֵל אַסֵּיפָא: נָזִיר שֶׁהָיָה טָמֵא בְּסָפֵק וּמוּחְלָט בְּסָפֵק — אוֹכֵל בְּקָדָשִׁים לְאַחַר שִׁשִּׁים יוֹם, וּמְגַלֵּחַ אַרְבַּע תִּגְלָחוֹת. וְהָא קָעָבֵיד הַקָּפָה! אָמַר שְׁמוּאֵל: בְּאִשָּׁה וְקָטָן.
Mar Zutra taught this halakha of Shmuel with regard to the latter clause of the following mishna (59b): A nazirite who has uncertain impurity and whose status as a confirmed leper is uncertain may eat sacrificial food after sixty days and shaves four times. One shaving is for his uncertain status as an impure nazirite, one is at the end of his term of naziriteship, and two are due to his status as a leper. A similar problem arose: But as he is not definitely obligated to shave, he violates the prohibition against rounding the head. Shmuel said: The mishna is referring to a woman or a minor boy, who are not prohibited from rounding their heads.
This should raise potential flags, since Mar Zutra, the colleague of Rav Ashi, is a sixth-generation Amora in Naresh. That is temporally distant from the first-generation Amora Shmuel.
Even so, matni lah is teaching a specific ruling in a specific form, and so we first have the gemara (potentially Ravina / Rav Ashi) teaching Shmuel’s statement as applying to the former clause of the Mishna, megalchin umevi`in, and now Mar Zutra teaching it in another fashion. Two late variants of the stama degemara, from the end period of Amoraim.
Searching for the two-word phrase זוטרא מתני, we find nine occurrences on Sefaria. Shabbat 23a (with Rav Shmuel bar Zutra), Shabbat 129a (with a nice contrast of Rav Ashi taught this way, Mar Zutra taught this way), with a second occurrence in the next line, Pesachim 10b (teaching Rav Yosef’s statement citing Rav Yehuda), Pesachim 120a (again teaching Rav Yosef, citing Rav Yehuda, citing Shmuel, in a particular manner), our sugya in Nazir (teaching a statement of Shmuel), Moed Katan 18b, Chullin 62a (teaching, perhaps teaching a variant of Ameimar), and Niddah 46a (again Rav Shmuel bar Zutra). So we can discard two of nine, one is a double, for a total of six occurrences.
Thus, Mar Zutra indeed works out.
However, this text is only what appears in printed editions. According to Hachi Garsinan, both Munich 95 and Vatican 110 have Mar Zutra son of Rav Nachman!
Thus, Vatican 110 has:
This Mar Zutra son of Rav Nachman is a fourth-generation Amora. He was a Gadol HaDor in the times of Rava, and both of them learned from his father, Rav Nachman bar Yaakov.
As Rav Nachman, in Nehardea, was a student of Shmuel, it makes some sense that he (or rather, his son carrying on such a tradition) would be able to frame Shmuel’s statement on the latter part of the Mishnah. So while the word and idea of מתני makes sense for plain Mar Zutra, in this instance Mar Zutra bereih deRav Nachman makes good sense. Also, the plain Mar Zutra is the more popular, and it makes little sense for a scribe to randomly insert a בריה דרב נחמן. We might have here the Pumpeditan approach to the suyga, vs. the Nehardean approach.
Some of the other Mar Zutra matni’s work best with the sixth-generation figure, plain Mar Zutra, where his approach contrasts with Rav Ashi. But, we should consider some of the others, where Rav Yosef, or Rav Yosef citing Rav Yehuda, all the way back to Shmuel are cited, and ruminate on whether Mar Zutra bar Rav Nachman makes sense there, and if there are any variant texts with this reading. (Pesachim 120 doesn’t have it.)