A Diachronic Account of Exceptional Progressive Nasalization Patterns in Guarani Causatives.

Nasal harmony in Paraguayan Guarani spreads mostly leftward in a morphological word. This regressive nasalization is triggered by a phonologically nasal consonant or stressed nasal vowel and does not affect voiceless stops. A limited process of progressive nasalization affects morpheme-initial voiceless stops across a morpheme boundary. Many forms that include a causative prefix show this kind of progressive nasalization. However, this nasal spread lacks any obvious nasal trigger and does not occur consistently. In this paper, I propose an explanation of these cases as vestiges of earlier phonological rules from pre-Proto-Tupi-Guarani but not active in Paraguayan Guarani, followed by the emergence of a regressive oralization rule and ending in a reanalysis of the basic form of the causative prefix. In so doing, I will provide a revised sequence of changes involving contour allophones in the reconstruction of Proto-Tupi-Guarani (PTG). [ABSTRACT FROM AUTHOR]