Eobrasilia coutoi Simpson, 1947, from fissure fillings of Paleocene age in the Itaborai Formation at Sao Jose de Itaborai, Brazil, was long thought to represent a possible "missing link" between the marsupial superfamilies Borhyaenoidea and Didelphoidea. The recent discovery from these same deposits of the anterior half of a right mandibular ramus with partial dentition representing the previously unknown lower dentition of E. coutoi, demonstrates that it is clearly a specialized didelphoid. The relative size and structure of P (sub 1-3) are similar to those seen in other didelphoids in the same fauna (e.g., Didelphopsis and Gaylordia) in which there occurs a reduced P 1 , and a large P 2 and enormous bulbous P 3 specialized for crushing. Similar specializations of the premolars occur in members of the marsupial family Stagodontidae from beds of Late Cretaceous age in North America. An unworn isolated right M 3 (or less likely M 2 ) from Itaborai is tentatively referred to E. coutoi.--Modified journal abstract.