Rondon’s Marmoset, Mico rondoni sp. n., from Southwestern Brazilian Amazonia
We describe Rondon’s marmoset (Mico rondoni sp. n.) from the Rio Jamari in the Brazilian state of Rondônia and differentiate the species from other Amazonian marmosets on the basis of morphological, genetic, and zoogeographic characteristics. Mico rondoni sp. n. is a typical bare-eared marmoset of predominantly grayish coloration and unpigmented face and cheiridia, which contrasts clearly with its more brownish and pigmented parapatric congeners Mico melanurus and M. nigriceps. Genetically, the new species is unquestionably distinct from Mico emiliae, with which it had been synonimized previously. The geographic range of the new species is defined as the area delimited by the Mamoré, Madeira, and Jiparaná rivers to the west, north, and east, respectively, and the Serra dos Pacaás Novos, to the south, where it is substituted by Mico melanurus. Depending on its exact limits, this range may cover an area of little more than 100,000 km2. A characteristic of the ecology of Mico rondoni sp. n. is its range-wide sympatry with the similarly sized tamarin Saguinus fuscicollis weddelli, which may be a key factor determining the rarity or absence of the new species from many areas within its geographic range. Its apparent scarcity may make the new species exceptionally vulnerable to the effects of the intense human colonization occurring throughout much of its known range, and provoke cause for concern for its long-term survival.