Callithrix is a genus of primates in the family Callitrichidae, subfamily Callitrichinae. Currently, the genus refers only to members of the "Jacchus Group" and they are endemic to eastern and central-western Brazil, occurring mainly in the Atlantic Forest. They have tufts on their ears, which can be used to differentiate species within the genus. They are popularly known as marmosets, being very popular animals as pets, due to their small size.