Most marmosets are about long. Compared to other monkeys, they have some primitive features. They have claws rather than nails, they lack wisdom teeth, and their brain layout seems to be relatively primitive. Their body temperature is unusually variable, changing by up to 4 °C (7 °F) in a day. Marmosets are native to South America and have been found in Bolivia, Brazil, Colombia, Ecuador, Paraguay and Peru. They have also been spotted in Central America.