Gros Ventre
Gros Ventre - Ahe or A'ananin to its own speakers - is an Algonkian language spoken today by only a handful of elders in Montana. Most linguists consider Gros Ventre a dialect of Arapaho, though the two tribes have distinct political and cultural identities. Gros Ventre had the unusual trait of being pronounced differently by male and female speakers--women used the sound "k" where men used "ty" or "ch." (Both genders, of course, could easily understand each other.) Gender dialects have not been preserved among the young Gros Ventre learning to speak their language again, so even if the language is successfully revived, it seems unlikely this feature will survive outside of a linguistics book.