This paper aims at describing a variety of a language, namely the Bonai Ulakpatian isolect
found in Riau Province. This study is a historical linguistic study that describes the process
of phonological innovation of retroplication and glottalization in an isolect used by the
Bonai etnic group in Ulakpatian Village, Rokan Hulu Regency. The analysis of
phonological innovation is based on the protomalayic (PM) reconstructed by Adelaar. This
study applies a deductive top-down analysis method. The data of research is data of speech
of society of Bonai etnic group which refers to 200 basic vocabularies which become
references in collecting linguistic data. The data were collected by applying conversation
method and listening method by using the elicitation technique and recording technique.
Data is phonetically described with the IPA symbol. The results are presented by formal
and informal methods. The results shows that the Bonai Ulakpatian isolect had a
phonological form of retroplexization at the end position of nasal alveolar nasal phoneme
/n / * PM into retrospective retardation [ţ] on isolate BU (* PM> BU), PM * n / - #> [ţ] ]
/ - #, and the glottalization of the initial position of the fristed alveolar phonemes without
sound /s / into glottal [h] on the BU (* PM> BU), PM * s / # -> [h] / # -
