split from the rest of the simian line about 40 million years ago (Mya), leaving the parvorder Catarrhini occupying the Old World. This latter group split about 25 Mya between the Cercopithecidae and the apes. This shows that the Cercopithecidae are closer related to the apes than to the Platyrrhini. Some lines of extinct simian also are either placed into the Eosimiidae (to reflect their Eocene origin) and sometimes in Amphipithecidae, thought to originate in the Early Oligocene. Additionally, Phileosimias is sometimes placed in the Eosimiidae and sometimes categorised separately. Classification The following is the listing of the various simian families, and their placement in the order Primates: Order Primates Suborder Strepsirrhini: nontarsier prosimians Suborder Haplorhini: tarsiers and monkeys, including apes Infraorder Tarsiiformes Infraorder Simiiformes Parvorder Platyrrhini: New World monkeys Family Callitrichidae: marmosets and tamarins Family Cebidae: capuchins and squirrel monkeys Family Aotidae: night or owl monkeys (douroucoulis) Family Pitheciidae: titis, sakis, and uakaris Family Atelidae: howler, spider, and woolly monkeys Parvorder Catarrhini Superfamily Cercopithecoidea: Old World monkeys Family Cercopithecidae Superfamily Hominoidea Family Hylobatidae: gibbons Family Hominidae: great apes, including humans †Amphipithecidae †Eosimiidae †Aseanpithecus Below is a cladogram with some of the extinct simian species with the more modern species emerging within the Eosimiidae. The simians originated in Asia, while the crown simians were in Afro-Arabia. It is indicated approximately how many Mya the clades diverged into newer clades. Usually the Ekgmowechashalidae are considered to be Strepsirrhini, not Haplorhini. A 2018 study places Eosimiidae as a sister to the crown haplorhini. In 2020 papers, the Proteopithecidae are part of the Parapithecoidea, and Nosmips aenigmaticus (previously in Eosimidae) is a basal simian. Biological key-features In a section of their 2010 assessment of the evolution of anthropoids (simians) entitled "What is an Anthropoid", Williams, Kay, and Kirk set out a list of biological features common to all or most anthropoids, including genetic similarities, similarities in eye location and the muscles close to the eyes, internal similarities between ears, dental similarities, and similarities on foot bone structure. The earliest anthropods were small primates with varied diets, forward-facing eyes, acute color vision for daytime lifestyles, and brains devoted more to vision and less to smell. Living simians in both the New World and the Old World have larger brains than other primates, but they evolved these larger brains independently. See also Simia, Carl Linnaeus's original classification of these primates. wikt:simianization References External links BioMed