The subfamily traditionally contained the guinea pig-like forms along with the cursorially-adapted (running) Kerodon.

The genus Kerodon contains two species of South American rock cavies related to capybaras.

Traditionally the genus Kerodon has been considered a member of the subfamily Caviinae along with the guinea pigs and other cavies.

Caviinae is a subfamily uniting all living members of the family Caviidae with the exception of the maras, capybaras and Kerodon.

In the caatinga of Brazil the native rodent Kerodon rupestris uses the exotic Brachiaria mutica as a food resource.

Like their relatives, the capybara and the maras, members of the genus Kerodon are highly social (Rowe and Honeycutt, 2003).

Molecular results have consistently suggested that Hydrochoerus is most closely related to Kerodon (the rock cavies), and that the two evolved from within the Caviidae.

Based on use of a molecular clock approach, Hydrochoerus appears to have diverged from Kerodon in the late Middle Miocene ( 12 Ma ago).

Recent molecular phylogenetic studies recognize a close relationship between Hydrochoerus and Kerodon, supporting placement of both genera in a subfamily of Caviidae.

Hydrochoerinae is a subfamily of Caviidae, consisting of two living genera, Hydrochoerus, the capybaras, and Kerodon, the rock cavies.

This led Woods and Kilpatrick (2005) to unite Kerodon and capybaras into the subfamily Hydrochoerinae within the Caviidae.

Using a molecular clock approach, Opazo (2005) suggested that Kerodon diverged from Hydrochoerus (the capybara) in the late Middle Miocene.

Molecular results suggest that the Caviinae as so defined would be paraphyletic and that Kerodon is more closely related to maras and capybaras than to other caviines (Rowe and Honeycutt, 2002).