Cytochrome b sequence of the Mazama americana jucunda Thomas, 1913 holotype reveals Mazama bororo Duarte, 1996 as its junior synonym.

The small red brocket deer, Mazama bororo Duarte, 1996 was described based on karyotypical and morphological characters. However, the original description of Mazama americana jucunda suggested that this subspecies could represent the same taxon as Mazama bororo. This assumption was based on the type locality of Mazama americana jucunda and on morphological similarities between Mazama americana jucunda and Mazama bororo. To solve this question, we obtained DNA sequences of the holotype of Mazama americana jucunda and compared it with other species of Mazama, including the holotype of M. bororo. A phylogenetic tree was obtained to verify the relationships among these taxa. The results clearly showed that M. americana jucunda and M. bororo represent the same biological entity. Therefore, the oldest name available for the small red brocket occurring in the Atlantic Forest of southern Brazil should be Mazama jucunda, remaining M. bororo as a junior synonym. We emphasise the importance of using DNA from museum specimens, especially from holotypes, in order to obtain a more accurate taxonomic identification. We also highlight the importance of application of valid names for labelling all aspects of biodiversity research, as well as for monitoring and conservation efforts.