The Pygmy Marmoset (Callithrix (Cebuella) pygmaea) is a monkey native to the rainforest canopies of western Brazil, southeastern Colombia, eastern Ecuador, and eastern Peru. It is one of the smallest primates, with its body length ranging from 14-16 cm (excluding the 15-20 cm tail). Males weigh around 140 g (5 ounces), and females only 120 g (4.2 ounces).

Despite its name, the Pygmy Marmoset is somewhat different from the typical marmosets classified in genus Callithrix. As such, it is accorded its own subgenus, which was formerly recognized as its own genus, Cebuella.

Pygmy Marmosets have a tawny coat, and ringed tails that are as long as their bodies. They are omnivorous, feeding on fruit, leaves, insects, and sometimes even small reptiles. Much of their diet, however, comes from tapping trees for sap. Up to two-thirds of their time is spent gouging tree bark to reach the gummy sap. Pygmy Marmosets have specialized incisors for gouging holes in bark. Unfortunately, because of its small size, and its swift movements, it is very hard to observe in the wild.

In captivity Pygmy Marmosets can live up to 11 years.

There are two subspecies of the Pygmy Marmoset:

• Callithrix (Cebuella) pygmaea pygmaea
• Callithrix (Cebuella) pygmaea niveiventris