Increased field collecting over the last few years, combined with the examination of historical collections in Uruguay, has resulted in the discovery of a great number of specimens of the Scelidotheriinae, indicating that this subfamily is better represented in Uruguay's Pleistocene fauna than previously thought. Because much of this new material is diagnostic, in this work we provide a fuller description of some specimens (a skull with associated mandible and the manus, another almost-complete skull, and two partial dentaries) from the late Pleistocene of Uruguay for which only preliminary descriptions have been previously made, with tentatively assignments to Catonyx. A discriminant analysis was performed using 48 adult specimens including Scelidotherium, Catonyx, and Proscelidodon and supports the contention that Catonyx is a valid genus and the inclusion of these new specimens within this genus. This analysis also allows us to identify those cranial characters that better differentiate the genera. The variables involved in the discriminant analysis are those related to the length of the skull, whereas variables related to the width have been excluded from the models or when included have had little significance to the analysis. We provide new optically stimulated luminescence (OSL) dates in the range of 16–32 ka that confirms the late Pleistocene age of the Dolores Formation, the source of these specimens. The described remains represent the first record of Catonyx cuvieri in Uruguay and the first evidence for the presence of the species outside Brazil.

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