Mico differs from Callithrix in dental morphology, genetics and geographic distribution: Callithrix species are distributed in eastern Brazil (mainly the Atlantic Forest), while Mico species are distributed in the Amazon south of Rio Madeira, though a single species, the black-tailed marmoset, also occurs in the Pantanal and Chaco.[4] Roosmalens' dwarf marmoset (Callibella humilis) was formerly considered a Mico species, but now has its own genus, Callibella, due mainly to differences in size[5] and genetics.[6] Roosmalens' dwarf marmoset is significantly smaller than the Mico species, being about midway between the typical Mico species and the pygmy marmoset, Cebuella pygmaea.[5] Mico species differ from the tamarins of the genus Saguinus in that Mico has enlarged incisor teeth the same size as the canine teeth which are used for gouging holes in trees to extract exudates.[7]