Abstract The notoungulate genus Puelia has a complex taxonomic history marked by uncertain familial placement and misidentified specimens. Examination of the holotype of Puelia plicata and unpublished upper and lower tooth material from several fossil localities provided new knowledge of both the genus and species. This study refines the diagnosis of P. plicata and expands our understanding of its anatomical and neuroanatomical variation. Puelia ranks among the smallest known toxodonts (12–17 kg) and displays a mosaic of cranio‐dental traits found in ‘notohippids’, ‘isotemnids’ and leontiniids. A virtual 3D brain endocast reveals a mix of primitive and derived characteristics typical of both Toxodontia and Typotheria. Features such as a large neocortex, bulging temporal lobes, and developed piriform lobes suggest enhanced sensory integration, particularly for olfaction and audition. A low encephalization quotient (EQ ≈ 0.4) aligns with broader notoungulate trends. Endocranial traits, including a triangular telencephalon, enlarged olfactory bulbs, and reduced sulcal complexity, resemble those of early Eocene taxa such as Periphragnis and Notostylops , but also some later Typotheria. These similarities should be interpreted as results of allometric scaling linked to small body size rather than close phylogenetic relationships. This underscores the role of size‐related convergence in shaping cranial and brain anatomy within Notoungulata. While the precise phylogenetic position of Puelia remains unresolved, its unique anatomical attributes offer key insights into early toxodontian evolution and the broader diversification of notoungulates. Integration of palaeoneurological and morphometric data proves essential for interpreting these evolutionary patterns.