Family Octodontidae Waterhouse, 1840 . Proc. Zool. Soc. Lond., 1839:172 [1840].

SYNONYMS: Spalacopidae.

COMMENTS: Includes Spalacopidae Lilljeborg, 1866. Sometimes considered the most primitive group of South American hystricognaths with numerous fossil genera from Oligocene on, but Reig (1986:418) reserved this distinction for the Echimyidae . Ctenomys is often placed here as subfamily, and is closely related to octodontids (see comments under Ctenomyidae and in Cook et al., 1990:22-23). Chromosomal variation is not as conservative as previously thought, and is 2n=38-102.