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Three genera of Tayassuidae are recognized in South America: Platygonus LE CONTE, 1848, Catagonus AMEGHINO, 1904 and Tayassu FISCHER, 1814. A material previously referred to the "Group Catagonus" and recently to Tayassu sp., was examined; in the light of the systematic scheme available today, it is identified as Catagonus stenocephalus (LUND in REINHARDT, 1880). The partial skull studied here is the first record of this species in the Touro Passo Stream, in outcrops of the Touro Passo Formation (Late Pleistocene), Uruguaiana, Rio Grande do Sul, Brazil. Therefore, it is extended its geographic distribution in South America, which was previously restricted to central-eastern Argentina, Lagoa Santa (Brazil) and Bolivia. From a palaeoenvironmental point of view, the presence of this species (presumably adapted to arid or semi-arid environments) in Touro Passo Formation, together with other faunistic remains (e.g., Holmesina paulacoutoi, Hydrochoerus hydrochaeris and Tapirus terrestris) adapted to warm-temperature and humid climatic conditions, and many other indicators of open to semi-open and perhaps arid or semi-arid environments (e. g., Glyptodon clavipes, Equus neogeus, Lama sp., Hemiauchenia paradoxa, Stegomastodon platensis) show a particular fauna. This fauna supports the palaeoenvironmental conditions that extended during Lujanian times throughout the Argentinian Mesopotamia, western Uruguay and southern Brazil. In these areas, the fauna was developed under more humid conditions that those recorded for the same age in the Pampean area, being the latter mostly cold and dry, and extending throughout north-central Argentina, Paraguay and part of Bolivia.