Family Caviidae
This family regroups all the true cavies and their relatives.

Dolichotis patagonum – Patagonian mara
Dolichotis salinicola – Chacoan mara

Family Hydrochaeridae
This monotypic family has been created for the Capybara.

Family Dasyproctidae
This family regroups all agoutis and related species.

Dasyprocta croconota – Orange agouti
Dasyprocta prymnolopha – Black-rumped agouti
Dasyprocta punctata – Central American agouti

Family Cuniculidae
This family regroups all pacas.

Cuniculus paca – Lowland paca

Family Octodontidae
This family regroups the degus and all its related species.

Family Myocastoridae
This monotypic family has been created for the Coypu.

Myocastor coypus – Coypu

Family Capromyidae
This family regroups all Hutias.

Family Chinchillidae
This family regroups all Chinchillas and Viscacha species.

Chinchilla lanigera – Long-tailed chinchilla