Coendou prehensilis (Lacépède 1799) is the extant prehensile-tailed porcupine. That marks it as primitive. This arboreal herbivore is protected by spine-like hairs.

Pectinator spekei (Blyth 1856) is Speke's pectinator, a species of rodent in the Ctenodactylidae native to Africa. This taxon nests between porcupines and chinchillas + capybaras. Note the reduced pedal digit 1 and the way the jugal wraps anteriorly around the orbit.

Neoreomys australis (Ameghinio 1891; Fields 1957; skeleton above from Scott 1905; UCMP 37973; Miocene, 18 mya; 1m long) is a large and common caviomorph rodent. Here it nests between porcupines and capybaras + Maiopatagium.

Chinchilla chinchilla (Bennett 1829) is the extant chinchilla, a rodent native to high elevations in the Andes mountains. It has the densest coat of all land mammals.

Hydrochoerus hydrochaeris (Brisson 1762; extant) is the largest living rodent, the capybara. Semiaquatic, highly social, polygynous and herbivorous, capybarasa are good-natured and able to hold their breath for up to 5 minutes underwater.

Dolichotis patagonum (Desmarest 1820, 70cm in length) is the extant Patagonian mara, an herbivorous rodent nesting in the LRT between guinea pigs and capybara. Resembling a jackrabbit, Dolichotis has a long antebrachium, long ears, a short tail and only three pedal digits. These diurnal herbivores run like deer. Young are raised in dens.

Cavia aperea (Erxleben 1777; 27cm) is the extant Brazilian guinea pig, an herbivore and smaller sister to the capybara.

Allactaga major (Cuvier 1836; Late Miocene to present; snout-vent length 5–15cm) is the extant jerboa, a nocturnal bipedal rodent that burrows into the sand during the day. The long hind limbs help it hop, like a kangaroo, zig-zagging over long distances, and avoid attacking owls. They can hurdle several feet in a single bounce. Some have short ears, others have giant ears for cooling. Closest relatives in the LRT include Chinchilla, not the traditional Mus.

Pedetes capensis (Illiger 1811; snout-vent length: 35-45cm) is the extant South African springhare, a diurnal burrower and a nocturnal hopper native to South Africa. By convergence it resembles a kangaroo. Pedal digit 1 is absent. Young are born with fur and are active within days.