Comparative and classificatory studies of Cariban languages, despite their long history (starting with Gilij in 1782), have been few and unsatisfactory, mainly due to the lack of necessary documentation of the languages in question. Based on a large amount of new descriptive data, as well as on published sources, the present work attempts to demonstrate the closer genetic relationship between a subgroup of three Cariban languages, Akuriyó, Tiriyó and Karihona, the last two of which were considered to belong to very distant branches of the family in a still widely cited classification (Durbin 1977). This demonstration takes the form of a reconstruction of the main aspects of the segmental phonology and inflectional morphology (person, number, evidentiality, tense/aspect/mood) of the proto-language, which the author proposes to call Proto-Taranoan. A preliminary etymological dictionary, as well as some remarks on the history of the speakers, is also included.