This taxon was traditionally thought to be a primitive stem lineage, from which all the larger bodied platyrrhines evolved (see Hershkovitz, 1977). However, Dr Susan Ford has argured quite convincingly that callitrichids are actually a dwarfed lineage. The ancestral callitrichid would likely have been a "normal" sized cebid that was dwarfed through evolutionary time. This may exemplify a rare example of insular dwarfing in a mainland context, with the "islands" being formed by the extensive river networks in the Amazon Basin, which form effective biogeographic barriers.
All callitrichines are arboreal. They are the smallest of the anthropoid (i.e. simian) primates. They eat insects, fruit, and the sap or gum from trees; occasionally they will take small vertebrates. The marmosets rely quite heavily on exudates, with several species (Callithrix jacchus and Cebuella pygmaea) considered obligate exudativores.
Callitrichines typically live in small, territorial groups of about 5 or 6 animals. They are the only primate group that regularly produce twins, which constitute over 80% of births in species that have been studied. Unlike other male primates, male hapalines generally provide as much parental care as females, more in some cases. Typical social structure seems to constitute a breeding group, with several of their previous offspring living in the group and providing significant help in rearing the young.
Studies in captivity, and the first field studies, suggested that the breeding group was invariably a single monogamous pair; subsequent field work on Brown-mantled Tamarins (Saguinus fuscicollis), has shown that many of the groups involve multiple males, and polyandry seems to be the commonest arrangement, though monogamous pairs do occur, and so, though rarely, does polygyny. In polyandrous groups, both (or all) the mature males regularly copulate with the female, and all contribute equally to parental care. It is now thought that this flexible system, with a tendency towards polyandry, may be the typical mating system among hapalines, though until field studies on more species have been completed any generalisation must be tentative.
Study data from University of California, Department of Orthopaedic Surgery update understanding of life sciences.
Feb 17, 2010; A report, 'The morphology of the masticatory apparatus facilitates muscle force production at wide jaw gapes in tree-gouging...