Crow is closely related to Hidatsa spoken by the Hidatsa tribe of the Dakotas; the two languages are the only members of the Missouri Valley Siouan family. The ancestor of Crow-Hidatsa may have constituted the initial split from Proto-Siouan. Crow and Hidatsa are not mutually intelligible, however the two languages share many phonological features, cognates and have similar morphologies and syntax. The split between Crow and Hidatsa may have occurred between 300 and 800 years ago.Graczyk, 2007: 2-3.Matthews, 1979: 113-25.Hollow and Parks, 1980: 68-97.
