Nawathinehena is extinct and Arapaho and Gros Ventre are both endangered.
Besawunena, only attested from a wordlist collected by Kroeber, differs only slightly from Arapaho, but a few of its sound changes resemble those seen in Gros Ventre. It had speakers among the Northern Arapaho as recently as the late 1920s.
Another reported Arapahoan variety is extinct Ha'anahawunena, but there is no documentation of it.
Goddard, Ives (2001). "The Algonquian Languages of the Plains." In Plains, Part I, ed. Raymond J. DeMallie. Vol. 13 of Handbook of North American Indians, ed. William C. Sturtevant. Washington, D.C.: Smithsonian Institution, pp. 71-79.
Marianne Mithun (1999). The Languages of Native North America. Cambridge Language Surveys. Cambridge: Cambridge University Press.