A phonetically “unnatural” class in Central and Eastern Shehret (Jibbali)

The set of consonants /b m y/ and historical *w in the Central and Eastern varieties of the Modern South Arabian language, Shehret (Jibbali), pattern together phonologically in the following ways: all are subject to intervocalic elision; between underlying /e/~/i/ and a stressed mid vowel, /b/ patterns with /m/ in being realised as [y]~[əy] in a range of words; /y/ is the reflex of historical *b in a closed set of lexemes; and /b/ realises historical *w, rarely *y, in pre-and post-consonantal position and in a handful of lexemes word-initially. Phonological interest in the set, /b m y/ *w, lies in the fact that the member consonants form a phonetically “unnatural” class (Mielke 2008): they do not include all and only labial consonants (lacking /f/, including /y/) nor all and only sonorants (lacking /l n r/, including /b/), including /b/), and two members of the set, /b y/, share no phonetic characteristics beyond ‘voice.’ Moreover, it is rare cross-linguistically for one obstruent to be subject to intervocalic elision to the exclusion of all other obstruents of that phonological class. Phonetically “unnatural” classes such as this are far from uncommon cross-linguistically (Mielke 2008), however; within Mielke’s (2008) Emergent Feature Theory, they can be accounted for by the pressures of phonetics and “external” factors. In this paper, we consider the patterning of /b m y/ *w, examine phonetic reasons for the inclusion of the plosive, /b/, in this set, and, based on Emergent Feature Theory, present a phonological account of the patterning of /b m y/ and *w.