Abstract

Caviomorph rodents, the New World Hystricognathi, are one of the most noteworthy groups of mammals in South America. Isolated for more than 30 Ma, they have given rise to several extraordinary rodents including the pacas (Cuniculusspp.), cavies (Caviaspp.), vizcachas (Lagostomusspp.), agouties (Dasyproctaspp.), as well as two giants: Phoberomys, from the late Miocene (6 Ma; mega annum = million years) which probably weighed more than 400 kg (Sánchez Villagra et al. 2003), and Josephoartigasia monesiprobably from the Pleistocene (2.5 Ma), at about 1,000 kg (Rinderknecht and Blanco 2008). Capybaras (Hydrochoerusspp.) are particularly conspicuous because of their size – they are the largest living rodents – and their aggregation in herds (Ojasti 1973; Macdonald 1981; Macdonald et al. 2007). This chapter examines their paleontology and evolution, focusing particularly on another striking feature: their unpaired ever-growing cheek teeth whose very complicated occlusal surface design changes throughout the capybara’s life (Vucetich et al. 2005).