Octodontidae Waterhouse 1839

Octodontidae Waterhouse 1839, Proc. Zool. Soc. Lond., 1839: 172.

Genera: 8 genera with 13 species:

Genus Aconaemys Ameghino 1891 (3 species)

Genus Octodon Bennett 1832 (4 species)

Genus Octodontomys Palmer 1903 (1 species)

Genus Octomys Thomas 1920 (1 species)

Genus Pipanacoctomys Mares, Braum, Barquez, and Diaz 2000 (1 species)

Genus Salinoctomys Mares, Braum, Barquez, and Diaz 2000 (1 species)

Genus Spalacopus Wagler 1832 (1 species with 3 subspecies)

Genus Tympanoctomys Yepes 1940 (1 species)

Discussion: 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 a 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, 2n=38-102 and includes the only known mammalian tetraploid (Gallardo et al., 1999). Molecular data (Gallardo and Kirsch, 2000; Honeycutt et al., 2003) support the monophyly of the Octodontidae and the sister taxon relationship with the Ctenomyidae .