Blurb:

Sahaptin and Nez Perce, the only two languages of the Sahaptian family, have a cognate obviative prefix with unusual allomorphy, which is argued to have been inherited from Proto-Sahaptian. Morpheme-specific allomorphy in each language is analyzed by positing allomorph sets, the choice among which is determined by phonological constraints. The analysis of Nez Perce relies on constraints on glottalized sonorants, whereas the analysis of Sahaptin makes use of sonority distance constraints and constraints against contiguous glottal stops. The article concludes with a proposed historical scenario for the development of the two languages, and discussion of the role of phonological constraints in the regulation of allomorphy.