Revalidation of Saguinus ursula Hoffmannsegg (Primates: Cebidae: Callitrichinae)

In this study, we review the taxonomy of Saguinus niger (E. Geoffroy) and revalidate Saguinus ursula Hoffmannsegg as a distinct species. The revalidation is based on pelage coloration, and the pattern of morphological divergence is corroborated by molecular data. Samples from the east bank of the Tocantins River ( S. ursulus ) were distinct from specimens of S. niger from the west bank in having mid-dorsal hair with an wide (5.0–55 mm) intermediary band of bright and golden buffy color; long (ca. 23–26 mm) dorsal hair at the inter-scapular region; and naked (not noticeably haired) face, hands and fingers. Saguinus ursulus and S. niger are allopatric, and Tocantins River is putatively acting as an effective barrier for gene flow. A lectotype to S. ursulus from syntypes was designated.