I always understood a major difference between a mishna/baraisa and the text of the gemarra is the former is in Rabbinic Hebrew and the latter is in Aramaic.
The other day I chanced upon a gemarra in Avodah Zara 23b:
ועוד תניא בהדיא מאי אותיבו ליה חברוהי לר' אליעזר (ישעיהו ס, ז) כל צאן קדר יקבצו לך יעלו (לרצון על) מזבחי
And furthermore, it is explicitly taught in a baraita: What did Rabbi Eliezer’s colleagues respond to him? They quoted a verse: “All flocks of Kedar shall be gathered together unto you...they shall come up with acceptance upon My altar” (Isaiah 60:7).
מאי אותיבו ליה חברוהי would seem evident that this baraisa is in Aramaic (it then quotes a verse in Hebrew).
Does anyone note/explain this curiosity? Are there other such cases in the gemarra (I guess besides the famous mishna Avos 2:6)?