Taxonomic review of the New World tamarins (Primates: Callitrichidae)

Twelve generic names have been ascribed to the New World tamarins but all are currently placed in just one: Saguinus Hoffmannsegg, 1807. Based on geographical distributions, morphology, and pelage patterns and coloration, they have been divided into six species groups: (1) nigricollis, (2) mystax, (3) midas, (4) inustus, (5) bicolor and (6) oedipus. Molecular phylogenetic studies have validated five of these groups; each are distinct clades. Saguinus inustus is embedded in the mystax group. Genetic studies show that tamarins are sister to all other callitrichids, diverging 15−13 Ma. The small-bodied nigricollis group diverged from the remaining, larger tamarins 11−8 Ma, and the mystax group diverged 7−6 Ma; these radiations are older than those of the marmosets (Callithrix, Cebuella, Mico), which began to diversify 6−5 Ma. The oedipus group diverged from the midas and bicolor groups 5−4 Ma. We review recent taxonomic changes and summarize the history of the generic names. Taking into account the Late Miocene divergence time (11−8 Ma) between the large- and small-bodied tamarin lineages, the small size of the nigricollis group species when compared with other tamarins, and the sympatry of the nigricollis group species with the larger mystax group species, we argue that the nigricollis group be recognized as a distinct genus: Leontocebus Wagner, 1839.