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 Sanguinus 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 enough 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. Taxonomic classification Following the taxonomic review of tamarins by Rylands et al. (2016) and Garbino & Martins-Junior (2018), there are 22 species in the genus Saguinus with 19 subspecies. Genus Saguinus Subgenus Saguinus Hoffmannsegg, 1807 S. midas group Golden-handed tamarin, midas tamarin, or red-handed tamarin, Saguinus midas Western black-handed tamarin or black tamarin, Saguinus niger Eastern black-handed tamarin, Saguinus ursulus S. bicolor group Pied tamarin, Saguinus bicolor Martins's tamarin, Saguinus martinsi Martins's bare-face tamarin, Saguinus martinsi martinsi Ochraceus bare-face tamarin, Saguinus martinsi ochraceus S. oedipus group Cotton-top tamarin or Pinché tamarin, Saguinus oedipus Geoffroy's tamarin, Saguinus geoffroyi White-footed tamarin, Saguinus leucopus Subgenus Tamarinus Trouessart, 1904 Moustached tamarin, Saguinus mystax Spix's moustached tamarin, Saguinus mystax mystax Red-capped tamarin, Saguinus mystax pileatus White-rump moustached tamarin, Saguinus mystax pluto White-lipped tamarin, Saguinus labiatus Geoffroy's red-bellied tamarin, Saguinus labiatus labiatus Thomas's red-bellied tamarin, Saguinus labiatus labiatus Gray's red-bellied tamarin, Saguinus labiatus labiatus Emperor tamarin, Saguinus imperator Black-chinned emperor tamarin, Saguinus imperator imperator Bearded emperor tamarin, Saguinus imperator subgrisescens Mottle-faced tamarin, Saguinus inustus Description