Graells's tamarin, Saguinus graellsi, is a species of tamarin

Tamarin

The tamarins are squirrel-sized New World monkeys from the family Callitrichidae in the genus Saguinus. They are closely related to the lion tamarins in the genus Leontopithecus.- Range :...

 from the northwestern Amazon

Amazon Rainforest

The Amazon Rainforest , also known in English as Amazonia or the Amazon Jungle, is a moist broadleaf forest that covers most of the Amazon Basin of South America...

 in southeastern Colombia

Colombia

Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

, eastern Ecuador

Ecuador

Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...

 and northeastern Peru

Peru

Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

. It has often been treated as a subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 of the Black-mantled Tamarin

Black-mantled Tamarin

The black-mantled tamarin, Saguinus nigricollis, is a species of tamarin from the northwestern Amazon in far western Brazil, southeastern Colombia and northeastern Peru. It has often included the Graells's Tamarin as a subspecies , but differs from that species in having reddish-orange rump and...

, but differs from that species in having a dull olive-brown (no reddish-orange) lower back, rump and thighs. The two are often said to be sympatric in Colombia (a major argument for treating them as separate species), though the accuracy of such reports has been questioned.