The Callitrichidae (also called Arctopitheci or Hapalidae) are a family of New World monkeys, including marmosets and tamarins. At times, this group of animals has been regarded as a subfamily, called Callitrichinae, of the family Cebidae. This taxon was traditionally thought to be a primitive lineage, from which all the larger-bodied platyrrhines evolved. However, some works argue that callitrichids are actually a dwarfed lineage.