Mini-Monkeys: The Odd One Out

Goeldi's monkey

Under the scheme that I have been using over the last year, there are 42 currently recognised species in the marmoset family. Of these, 22 are marmosets, and 19 are either tamarins or lion tamarins. It doesn't require much arithmetic to deduce that there must therefore be one member of the family that's neither.

This is Goeldi's monkey (Callimico goeldii). It is sometimes called "Goeldi's marmoset", or, less commonly, "Goeldi's tamarin", but these names are misleading and inaccurate. It is, undoubtedly, a member of the marmoset family, but it's equally clear that it is quite different from anything else within that family.

First, the similarities. Goeldi's is about the same size, at about 25 cm (10 inches) in body length, as other members of the family, and therefore much smaller than any monkeys outside the family. It has similarly luxuriant fur, in its case almost entirely black, with an almost mane-like ruff around the head. Like members of the marmoset family, but unlike other monkeys, it has claws, rather than nails - something it uses to cling on to rough bark. It also lives in roughly the same area, in the high altitude western margin of the Amazon, from Colombia down to Bolivia and in to western Brazil.