Equidae
Equidae (sometimes known as the horse family) is the taxonomic family of horses and related animals, including the extant horses, donkeys, and zebras, and many other species known only from fossils. All extant species are in the genus "Equus". Equidae belongs to the order Perissodactyla, which includes the extant tapirs and rhinoceros, and several extinct families.
Caviinae
Caviinae is a subfamily uniting all living members of the family Caviidae with the exception of the maras, capybaras, and "Kerodon". The subfamily traditionally contained the guinea pig or cavy-like forms along with the cursorially adapted (running) "Kerodon". Molecular results suggest the Caviinae as so defined would be paraphyletic and "Kerodon" is more closely related to maras and capybaras than to other caviines. This led Woods and Kilpatrick (2005) to unite "Kerodon" and capybaras into the subfamily Hydrochoerinae within the Caviidae. These studies also suggest "Microcavia" and "Cavia" are more closely related to one another than either is to "Galea".