Goeldi's Monkey or Goeldi's Marmoset (Callimico goeldii)

Isla de los Monos, Indiana, Iquitos, Loreto, Amazonian rainforest, Amazon River, Amazonia, Peru

Goeldi's Marmosets prefer to forage in dense scrubby undergrowth; perhaps because of this, they are rare, with groups living in separate patches of suitable habitat, separated by miles of unsuitable flora. In the wet season, their diet includes fruit, insects, spiders, lizards, frogs, and snakes. In the dry season, they feed on fungi, the only tropical primates known to depend on this source of food. They live in small social groups (approximately six individuals) that stay within a few feet of one another most of the time, staying in contact via high-pitched calls.

Source Wikipedia

The first who described this species was Emil Goeldi, of Swiss origin, later Swiss-Brazilian citizen, which was born quite near where I grew up myself. http://en.wikipedia.org/wiki/Emil_August... Actually unlike from the german name might be expected is not a kind of tamarin. They have unlike other species of Callitrichidae 6 molar teeth in both the maxilla and mandibula.