Saguinus

The tamarins are squirrel-sized New World monkeys from the family Callitrichidae in the genus Saguinus. They are the first offshoot in the Callitrichidae tree, and therefore are the sister group of a clade formed by the lion tamarins, Goeldi's monkeys and marmosets.

==Taxonomy and evolutionary history== Hershkovitz (1977) recognised ten species in the genus Saguinus, further divided into 33 morphotypes based on facial pelage. A later classification into two clades was based on variations in dental measurements. A taxonomic review (Rylands et al., 2016) showed the tamarins are a sister group to all other callitrichids, branching off 15–13 million years ago. Within this clade, six species groups are historically recognised, nigricollis, mystax, midas, inustus, bicolor and oedipus, five of which were shown to be valid with Saguinus inustus placed within the midas group. The review noted that the smaller-bodied nigricollis group began diverging 11–8 million years ago, leading the authors to move them to a separate genus, Leontocebus (saddle-back tamarins). While a 2018 study proposed that Leontocebus does not have sufficient divergence from Saguinus to be in its own genus, and thus should be reclassified it as a subgenus of Saguinus, this proposal has since found significant traction. The same study found the mystax group of tamarins to be distinct enough to be classified in the subgenus Tamarinus. As of 2021 this proposal has not been universally accepted by primatologists.