The Yǒng’ān 永安 dialect, spoken in central Fújiàn, is notable for having a very peculiar phonological feature: so-called closed-mouth finals (bìkǒuyùn 閉口韻), wherein the mouth is already closed when the articulation of the final starts. The Yǒng’ān dialect is classified as Central Mǐn 閩 by Norman (1991), together with closely related dialects spoken in Sānmíng 三明 and Shāxiàn 沙縣. Unlike in Yǒng’ān, however, closed-mouth finals appear in the Sānmíng dialect only very sporadically and do not appear at all in Shāxiàn, nor in any other known Chinese dialect.

Norman (1971) first used the t…