Marmosets
Marmosets are the smallest of all true monkeys and seem to have moved from the basic monkey life style to that of a squirrel; eating nuts, catching insects and licking sap from bark gnawed by their special forward-pointing incisors. The pygmy marmoset (Cebuella pygmaea) has a body length of 100 mm and runs along branches, keeping a foothold on the bark with claws. Use of claws is a recent reversion, for the embryonic marmoset begins to develop monkey nails on its fingers and only later do they develop into claws.

Common Marmoset (Callithrix (Callithrix) jacchus)