Marmoset , common name for certain long-tailed, tropical American monkeys that differ from other monkeys in having two instead of three molars on each side of the upper jaw and in having long, curved claws (rather than nails) on all the toes except the great toe. Marmosets also have nonopposable thumbs. The animals all have soft, silky fur and are gentle in disposition; many have long fringes of hair on the ears. They are arboreal and feed on fruits and insects. Litters contain one to three young. Marmosets are divided into five groups: the true marmosets; the tamarins; the pygmy marmosets; the golden tamarins; and Goeldi's marmoset, which retains the third molar. The true marmosets, also known as short-tusked marmosets or titis, are generally smaller than the tamarins. The best known of the true marmosets is the common marmoset. It is 18 to 30 cm (7 to 12 in) in body length, and has a round head with a flattened black face, thick white tufts on its ears, and long black and white fur. The tail, which is almost twice as long as the body, is white ringed with black. Most marmosets are endangered as a result of loss of habitat .