Callimico

Callimico is a monotypic genus of New World monkeys of the family Callitrichidae whose only species is Goeldi's marmoset, or Goeldi's monkey (Callimico goeldii), found mainly in the upper Amazon basin of Bolivia, Brazil, Colombia and Peru. It was first described in 1904, which makes it one of the more recent monkey genera to be described. Older classifications sometimes placed it in a family of its own and sometimes, with the marmosets and tamarins, in the subfamily Callitrichinae of the family Cebidae; molecular phylogenetics now shows that it evolved from an ancestral callitrichine and is a sister taxon of the marmosets. Unlike most other members of the family, which usually give birth to twins, the mother carries a single baby per pregnancy, and one argument holds that the genus conserves primitive traits such as single births and a third molar that many marmosets have lost.