Marmoset
The marmosets (), also known as zaris or sagoin, are 22 New World monkey species of the genera "Callithrix", "Cebuella", "Callibella", and "Mico". All four genera are part of the biological family Callitrichidae. The term "marmoset" is also used in reference to Goeldi's marmoset, "Callimico goeldii", which is closely related. Most marmosets are about long. Relative to other monkeys, they show some apparently primitive features; they have claws rather than nails, and tactile hairs on their wrists. 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 occasionally spotted in Central America and southern Mexico. They are sometimes kept as pets, though they have specific dietary and habitat needs that require consideration. According to recent research, marmosets exhibit germline chimerism, which is not known to occur in nature in any primates other than callitrichids. 95% of marmoset fraternal twins trade blood through chorionic fusions, making them hematopoietic chimeras. Etymology. "Callithrix" comes from Ancient Greek and  means "beautiful fur". Behavior. Marmosets are highly active, living in the upper canopy of forest trees, and feeding on insects, fruit, leaves, tack, sap, and gum. They have long lower incisors, which allow them to chew holes in tree trunks and branches to harvest the gum inside; some species are specialised feeders on gum. Marmosets live in family groups of three to 15, consisting of one or two breeding females, an unrelated male, their offspring, and occasionally extended family members and unrelated individuals. Their mating systems are highly variable and can include monogamy, polygyny, and polyandry. In most species, fraternal  twins are usually born, but triplets are not unknown. Like other callitrichines, marmosets are characterized by a high degree of cooperative care of the young and some food sharing and tolerated theft. Adult males, females other than the mother, and older offspring participate in carrying infants. Father marmosets are an exceptionally attentive example of fathers within the animal kingdom, going as far as assisting their mates in giving birth, cleaning up afterbirth, and even biting the umbilical cords attaching their newborn offspring to their mothers. Most groups scent mark and defend the edges of their ranges, but if they are  truly territorial is unclear, as group home ranges greatly overlap. The favorite food of marmosets is carbohydrate-rich tree sap, which they reach by gnawing holes in trunks. Their territories are centered on the trees that they regularly exploit in this way. The smaller marmosets venture into the very top of forest canopies to hunt insects that are abundant there.