One of the basal Glyptodontidae groups is represented by the Propalaehoplophorinae (late Oligocene — middle Miocene), whose genera (Propalaehoplophorus, Eucinepeltus, Metopotoxus, Cochlops, andAsterostemma) were initially recognized in Argentinian Patagonia. Among these,Asterostemma was characterized by its wide latitudinal distribution, ranging from southernmost (Patagonia) to northernmost (Colombia, Venezuela) South America. However, the generic assignation of the Miocene species from Colombia and Venezuela (A.? acostae, A. gigantea, andA. venezolensis) was contested by some authors, who explicitly accepted the possibility that these species could correspond to a new genus, different from those recognized in southern areas. A new comparative study of taxa from Argentinian Patagonia, Colombia and Venezuela (together with the recognition of a new genus and species for the Pliocene of the latter country) indicates that the species in northern South America are not Propalaehoplophorinae, but represent the first stages in the cladogenesis of the Glyptodontinae glyptodontids, the history of which was heretofore restricted to the late Miocene — early Holocene of southernmost South America. Accordingly, we propose the recognition of the new genusBoreostemma for the species from northern South America and the restriction ofAsterostemma to the Miocene of Patagonia. Thus, the available data indicate that the Glyptodontinae would in fact have arisen in the northernmost regions of this continent. Their arrival to more southerly areas coincides with the acme of the “Age of Southern Plains”. The Propalaehoplophorinae are geographically restricted to Patagonia.