Pygmy marmoset

Pygmy marmosets are the smallest marmosets and one of the smallest of all primates. They inhabit Brazil, Ecuador, Peru and Colombia. Most pygmy marmosets lives in troops of two to nine individuals, with a dominant male, a breeding female, and up to four successive litters of offspring. The modal size of a standard stable troop would be 6 individuals.
Pygmy marmosets have tawny agouti fur (the tip of the hair is a different color to the base) with an indistinctly dark-ringed tail. They can range in size from 4.6 in to 6 in but could possibly be half that size when they are first born since they are the size of a human thumb.
They are expected to live as long as 15-20 years. 
Habitat.
They live in flooded forest near rivers, bamboo thickets and the edges of agricultural fields. They're mostly native in South Africa but can also be found around the western part of the amazon rainforest. Can also be found in Bolivia, Peru, Columbia, and Western Brazil. 
Diet.
Pygmy marmosets mainly feed on gum (tree exudates, sap), but they also eat fruit, nectar and insects. They gouge holes in the bark of trees, and revisit these holes daily to collect the sap. The marmosets hang on with specially adapted claws.
References.
2. Tardif , S., Smucny , D., Abbott , D., Mansfield , K., Darkin, N. S., &amp; Yamamoto , M. E. (2003). National Library of Medicine . Reproduction in Captive Common Marmosets (Callithrix Jacchus), 364–368.
3. University of Salford. (2018, February 27). Smallest monkey's evolutionary secret. ScienceDaily. Retrieved October 19, 2021 from www.sciencedaily.com/releases/2018/02/180227094726.htm
4. Jean P. Boubli, Maria N.F. da Silva, Anthony B. Rylands, Stephen D. Nash, Fabrício Bertuol, Mário Nunes, Russell A. Mittermeier, Hazel Byrne, Felipe E. Silva, Fabio Röhe, Iracilda Sampaio, Horacio Schneider, Izeni P. Farias, Tomas Hrbek, How many pygmy marmoset (Cebuella Gray, 1870) species are there? A taxonomic re-appraisal based on new molecular evidence, Molecular Phylogenetics and Evolution, Volume 120