The eastern pygmy marmoset (''Cebuella niveiventris'') is a
marmoset
The marmosets (), also known as zaris or sagoin, are 22 New World monkey species of the genera '' Callithrix'', '' Cebuella'', '' Callibella'', and '' Mico''. All four genera are part of the biological family Callitrichidae. The term "marmoset" ...
species
In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
, a very small
New World monkey
New World monkeys are the five families of primates that are found in the tropical regions of Mexico, Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Ceboid ...
, found in the southwestern
Amazon Rainforest in Bolivia, Brazil, Ecuador, and Peru. It was formerly regarded as
conspecific
Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species.
Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organ ...
with the similar
western pygmy marmoset, but the eastern pygmy marmoset has whitish colored underparts. Although the eastern pygmy marmoset occurs further east than the western pygmy marmoset, the primary separators of their ranges are the
Amazon River (
Solimões River) and
Maranon River, with the western occurring to the north of them and the eastern to the south.
The species has recently been confirmed by DNA testing to exist in Ecuador, hundreds of kilometers north of the Maranon River.
Physical Description
The eastern pygmy marmoset weighs around 119 grams and have a head size ranging from 33.7 to 38.9mm, being one of the smallest New World monkeys.
In the wild, full grown adult males weigh approximately 110 grams whereas adult females can weigh around 120 grams.
All
pygmy marmosets share a common attribute where they have a mane of fur covering their ears, arms that are longer than their hind legs, and they have no
protocone in their first upper
premolar tooth.
Due to their specific diet, the eastern pygmy marmoset also has large lower
incisor
Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, w ...
s and a strong V-shaped lower jaw.
The eastern pygmy marmoset also has claw-like nails which are beneficial for actions such as poking holes in tree bark to obtain food, as well as the claw-like nails allows them to cling vertically to tree trunks.

As different subspecies of the pygmy marmoset have different coloration patterns, the eastern pygmy is more of a white, pale color.
The species has whiteish underparts which include their arms and legs, as well as their throat and chest having a more orange to white coloration.
Ecology
Distribution
The eastern pygmy marmoset are small arboreal nonhuman primates that cover a large geographic distribution.
As it was confirmed by DNA the eastern pygmy marmoset is located primarily south of the Rio Solimões river (Amazon River) covering parts of Peru, Brazil, Equator and Bolivia.
The species covers a larger range in Brazil and Peru, present in the Amazonian lowlands an
Andean foothills The home range of this nonhuman primate also stretches a little into northern Bolivia.
Diet
The eastern pygmy marmoset is similar to the general species as they have a specific high-quality, rare food diet.
They are considered mainly to be exudativores as well as
insectivore
A robber fly eating a hoverfly
An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects.
The first vertebrate insectivores wer ...
s.
The eastern pygmy marmosets feed primarily on plant exudates which consist of tree sap, tree gum as well as latex from trees and
liana
A liana is a long- stemmed, woody vine that is rooted in the soil at ground level and uses trees, as well as other means of vertical support, to climb up to the canopy in search of direct sunlight. The word ''liana'' does not refer to a ...
s.
This consists of a large portion of their diet.
They are known at times to also eat
arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...
s, primarily being insects, and occasionally eat fruits for extra nutrition.
The species, due to their particular diet, has dental as well as nail adaptations in order to gnaw, dig, and cling vertically to trees; these are all behaviors associated with feeding as well as exudate foraging.
References
{{Taxonbar, from=Q95573837
Cebuella
Mammals described in 1940
Primates of South America
Taxa named by Einar Lönnberg