The Taxonomic Status of Mico marcai (Alperin 1993) and Mico manicorensis (van Roosmalen et al. 2000) (Cebidae, Callitrichinae) from Southwestern Brazilian Amazonia Guilherme Siniciato Terra Garbino Received: 03 December 2013 /Accepted: 11 January 2014 # Springer Science+Business Media New York 2014 Abstract Species level taxonomic revisions of New World monkeys are scarce but necessary if we are to obtain a clear picture of this group’ s diversity. In this work I revise taxonomically the little known marmoset Mico marcai¸ originally described as Callithrix argentata marcai Alperin, 1993, in light of more recently collected material. I show that this species is significantly different in facial pigmentation and pelage color from all other marmosets of the genus Mico in the Madeira–Tapajós interfluvium. The form first described as Callithrix manicorensis is treated as a junior synonym of Mico marcai, as there are no morphological differences or geographical barriers between the two putative taxa. Mico marcai occurs in the Aripuanã–Manicoré interfluvium, limited in the north by the Rio Madeira and in the south by enclaves of savannah vegetation. Mico marcai occurs in sympatry with Callibella humilis through at least part of its range, representing the only known case of sympatry of two species of marmoset. The northern range of Mico marcai is relatively undisturbed and has few human settlements, its southern limit, on the other hand, is crossed by a major Brazilian highway, and in the same region at least seven hydroelectric reservoirs are planned to be built. Keywords Callitrichinae . Mico manicorensis . Mico marcai . Taxonomy Introduction The number of recognized New World primate species has more than doubled in the last 30 years, and much of this increase is the result of traditional taxonomic revisions (Groves 2001b). Among callitrichines, a great increase in recognized species was due Int J Primatol DOI 10.1007/s10764-014-9766-4 G. S. T. Garbino (*) Museu de Zoologia da Universidade de São Paulo, Ipiranga 04263-000 São Paulo, Brazil e-mail: gstgarbino@hotmail.com G. S. T. Garbino Pós-graduação, Museu de Zoologia, Universidade de São Paulo, CEP 04263-000 São Paulo, SP, Brazil