Octodontids are medium sized rodents, ranging from in body length. They have long, silky, fur, which is typically brownish in color, and often paler on the underside. The name 'octodont' derives from the wear pattern of their teeth, which resembles a figure 8. Most are nocturnal, social, burrowing animals, though the Degu is largely diurnal. They are herbivorous, eating tubers, bulbs, and cactuses.
Some authors have suggested that the octodontids should be reclassified in the order Lagomorpha, but this has not been supported by further analyses (e.g. Opazo, 2005). Older literature includes the tuco-tucos in the family, as the subfamily Ctenomyinae, but these animals are normally now treated as a separate family, the Ctenomyidae. Two of the genera now included in this family, Salinoctomys and Pipanacoctomys, have only recently been described. There is some evidence that evolution within the family may have resulted from polyploidy. The red viscacha rat, Tympanoctomys barrerae, is tetraploid, with 102 chromosomes, and the recently described golden viscacha rat Pipanacoctomys aureus has 92.
Members of the genus Aconaemys are referred to as rock rats, and members of genus Octodon are all called degus, though the name Degu on its own implies O. degu. The single member of Spalacopus, S. cyanus, is called the Coruro. Members of the other genera are called viscacha rats: note, however, that viscachas are not octodontids - they are members of the chinchilla family Chinchillidae.
Genus Octodon Bennett, 1832 (Degus).
Genus Octodontomys Palmer, 1903.
Genus Octomys Thomas, 1920.
Genus Pipanacoctomys Mares et al., 2000.
Genus Salinoctomys Mares et al., 2000.
Genus Spalacopus Wagler, 1832.
Genus Tympanoctomys Yepes, 1942.