[1] Voegelin proposes that Biloxi, Ofo and Tutelo consistute one group which he terms Ohio Valley Siouan.

This group includes various historical languages spoken by Siouan peoples not only in the Ohio River Valley, but across the Appalachian Plateau and into the Piedmont regions of present-day Virginia and the Carolinas.

Some of these groups migrated or were displaced great distances following European contact, ending up as far afield as present-day Ontario and southern Mississippi.

[6] Many of the consonant clusters proposed by Wolff (1950–1951) can be accounted for due to syncopation of short vowels before stressed syllables.

With added data from a larger set of Siouan languages since the middle of the twentieth century, Rankin et al. (2015) give *waroː(-ka) as the reconstructed form for 'male.'

The actual phonetic value of these obstruents is an issue of some debate, with some arguing that they arise through geminated *w+*w or *r+*r sequences or a laryngeal plus *w or *r.[8] Previous work on Proto-Siouan only posited single vowel length.

The proposed Proto-Siouan vowel system appears below: The Yuchi isolate may be the closest relative of Sioux–Catawban, based on both sound changes and morphological comparison.

In 1931, Louis Allen presented the first list of systematic correspondences between a set of 25 lexical items in Siouan and Iroquoian.