The black-tailed marmoset (Mico melanurus) is a species of New World monkey from central South America, where it ranges from the south-central Amazon in Brazil, south through the Pantanal and eastern Bolivia, to the Chaco in far northern Paraguay.
The black-tailed marmoset is dark brown with paler foreparts and a black tail. Unlike most of its relatives, it has a striking white or yellow-white stripe that extends down its thigh.