It is the new world monkey

New world monkey's

a New World Monkey is a platyrrhine primate

It depends, if it has a tail it's a new world monkey from the jungles of south America and the carribean, if it doesn't its an old world monkey from the plains or jungles of Africa.

The name of the monkey that is the size of your thumb is the marmoset monkey. The marmoset monkey is a new world monkey. ( The two categories of monkeys being Old World Monkeys and New World Monkeys. From then on they are classified into their species.) They have flat round nostrils and are VERY CUTE!