ABSTRACT In this report, the first installment of a comprehensive revision of the didelphid marsupial genus Marmosops, we revise the species of the subgenus Sciophanes. Based on morphological character variation among almost 300 examined specimens—which we interpret in the context of a previously published analysis of molecular sequence data—this revision recognizes 12 valid species in three monophyletic species groups: the Parvidens Group (including M. pakaraimae, M. parvidens, and M. pinheiroi), the Fuscatus Group (M. carri, M. fuscatus, M. handleyi, and M. invictus), and the Bishopi Group (M. bishopi, M. juninensis, M. ojastii, and two new species). For each species we summarize information about type material, ecogeographic distribution, and diagnostic morphological characters. Despite our diligent search for relevant material in North and South American museums, the absence of any specimens of Sciophanes from vast Amazonian and Andean landscapes with seemingly suitable habitat suggests that significa...