Lesson's saddle-back tamarin

Lesson's saddle-back tamarin (Leontocebus fuscus) is a species of saddle-back tamarin, a type of small monkey from South America. Lesson's saddle-back tamarin was formerly considered to be a subspecies of the brown-mantled tamarin, L. fuscicollis. Genetic analysis showed it to be more closely related to the black-mantled tamarin than to the brown-mantled tamarin. Its type locality is in Colombia, in Plaines de Mocoa, Putumayo, between the Rio Putumayo and Rio Caqueta. It also lives in Brazil.

Lesson's saddle-back tamarin has a head and body length of between 212 mm and 234 mm. Males have tails between 296 mm and 383 mm long, and females have tales between 337 mm and 362 mm long. It weighs between 350 g and 400 g.

It sometimes associates with Goeldi's marmoset. The IUCN rates it as least concern from a conservation standpoint.