Articulatory taxonomy of mammalian buccolabial oral tracts: On sources of apparent vowel-like quality

Supralaryngeal vocal tracts of nonhuman mammals do not support production of the extent of human vowels, nor do nonhuman mammals apparently employ their tongues while vocalizing. Yet, vocalizations by nonhuman mammals nonetheless exhibit a range of vowel-like qualities, typically ranging from schwa (unstressed vowel) to apparently /u/-like formant dispersions. I suggest a rudimentary distinction, with three disparate and distinguishable modes of oral tract articulation. The long faces of canines, felines, baboons, and various other mammals, with labial commissures stretched around the skull offer the ability to effectively (a) shorten and/or “flare”, or (b) elongate and narrow the oral tract, with degrees of jaw height: (1) the Prognathic-Mandibular form, common to many mammalian species. Higher primates can apparently achieve (a) in similar ways to other mammals, and (b) through protrusion and rounding of the anteriormost section of the oral cavity, through control of flexible lips: (2) the Prognathic-Labial form, common to higher primates. Human articulation, finally, is characterized by intraoral execution of articulatory gestures employing the tongue, and downstream greater ease of coarticulation and ability to actively “underexploit” relevant parameters: (3) the Orthognathic-Lingual form. The phenomenon of non-human animals’ achieving vowel-like quality via non-lingual gestures is here termed quasi-phonemic coasting.