Lesson's saddle-back tamarin

{{Short description|Species of tamarin}}

{{Speciesbox

| name = Lesson's saddle-back tamarin

| image = Saguinus-fuscicollis-Humboldt-Zoologie-T05p74.png

| image_caption =

| status = LC

| status_system = IUCN3.1

| status_ref = {{cite iucn |author=Palacios, E. |author2=Spironello, W.R. |date=2020 |title=Leontocebus fuscus |volume=2020 |page=e.T42693A17980668 |doi=10.2305/IUCN.UK.2020-3.RLTS.T42693A17980668.en |access-date=19 November 2021}}

| genus = Leontocebus

| species = fuscus

| authority = (Lesson, 1840)

| range_map = Saguinus_fuscus_MDD_Range.png

| range_map_caption = Approximate range of the 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.{{cite journal |author1=Rylands, Anthony B. |author2=Eckhard W. Heymann |author3=Jessica Lynch Alfaro |author4=Janet C. Buckner |author5=Christian Roos |author6=Christian Matauschek |author7=Jean P. Boubli |author8=Ricardo Sampaio |author9=Russell A. Mittermeier | year=2016 | title=Taxonomic Review of the New World Tamarins (Primates: Callitrichidae) | journal=Zoological Journal of the Linnean Society | volume=177 | issue=4 | pages=1003–1028 | doi=10.1111/zoj.12386|url=http://socgen.ucla.edu/wp-content/uploads/2016/02/Rylands-et-al-Review-of-tamarin-taxonomy-J-Zool-Linn-Soc-2016.pdf|access-date=2020-04-19}}{{cite book|title=All the World's Primates|author1=Porter, Leila M.| author2=Dacier, Anand |editor=Rowe, Noel |editor2=Myers, Marc|page=333|year=2016|publisher=Pogonias Press|isbn=9781940496061}} 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 Department|

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 {{convert|212|mm|in}} and {{convert|234|mm|in}}. Males have tails between {{convert|296|mm|in}} and {{convert|383|mm|in}} long, and females have tales between {{convert|337|mm|in}} and {{convert|362|mm|in}} long. It weighs between {{convert|350|g|oz}} and {{convert|400|g|oz}}.

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