This article is concerned with a restricted number of literary quotations whose transmission seems to derive from Pliny’s Dubius sermo even when they are not explicitly attributed to this author. Some shared characteristics, concerning the grammatical sources in which they appear and the authors quoted (historians, orators, later poets, Augustan critics and men of letters, epistolary texts, Augustus, res naturales and technical texts) make it possible to identify a homogeneous ‘micro-corpus’ and a new function of auctoritas in the history of Latin grammar.