In several publications on Tunica, an extinct language once spoken in Louisiana, Mary Haas (1950, 1944) presents a vowel inventory which consists of seven phonemes. A close study of the morphophonemic alternations within the language suggests that there were only five underlying vowels and that the occurrence of [ɛ] and [ɔ] was predictable. In this paper, I will attempt to demonstrate that [ɛ] and [ɔ] are derived in two ways: (1) vowel coalescence and (2) assimilation. I will discuss the effects of each of these processes separately.
Latimer, R. (1978). Another look at Tunica vowels. Calgary Working Papers in Linguistics, 4(Spring), 45-50.