The simians, anthropoids, or higher primates are an

infraorder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between Family_(biology), family and Class_(biology), class. In biological classification, the order is a taxonomic rank used in the classific ...

(Simiiformes ) of

primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...

s containing all animals traditionally called

monkey Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes. Thus monkeys, in that sense, co ...

s and

ape Apes (collectively Hominoidea ) are a superfamily of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and Europe in prehistory, and counting humans are found global ...

s. More precisely, they consist of the

parvorder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...

s Platyrrhini (New World monkeys) and

Catarrhini The parvorder Catarrhini (known commonly as catarrhine monkeys, Old World anthropoids, or Old World monkeys) consists of the Cercopithecoidea and apes (Hominoidea). In 1812, Geoffroy grouped those two groups together and established the name ...

, the latter of which consists of the family Cercopithecidae (

Old World monkey Old World monkeys are primates in the family Cercopithecidae (). Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons (genus '' Papio''), red colobus (genus '' Piliocolob ...

s in the stricter sense) and the superfamily

Hominoidea Apes (collectively Hominoidea ) are a Family (biology), superfamily of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and Europe in prehistory, and counting humans ...

(apesincluding humans). The simians are sister group to the

tarsiers Tarsiers ( ) are haplorhine primates of the family Tarsiidae, which is the lone extant family within the infraorder Tarsiiformes. Although the group was prehistorically more globally widespread, all of the existing species are restricted to Ma ...

(Tarsiiformes), together forming the haplorhines. The

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes: * ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...

occurred about 60 million years ago (during the

Cenozoic era The Cenozoic Era ( ; ) is Earth's current geological Era (geology), era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, Insect, insects, birds and flowering plant, angiosperms (floweri ...

); 40 million years ago, simians colonized

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

, giving rise to the

New World monkey New World monkeys are the five families of primates that are found in the tropical regions of Mexico, Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Ceboi ...

s. The remaining simians (catarrhines) split about 25 million years ago into

Cercopithecidae Old World monkeys are primates in the family (biology), family Cercopithecidae (). Twenty-four genus, genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons (genus ''Papio''), red colo ...

and

s (including

human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

s).

Taxonomy

In earlier classification, New World monkeys, Old World monkeys, apes, and humans – collectively known as simians or anthropoids – were grouped under Anthropoidea (; ), while the strepsirrhines and tarsiers were grouped under the suborder "

Prosimii Prosimians are a group of primates that includes all living and extinct strepsirrhines (lemurs, lorisoids, and adapiforms), as well as the haplorhine tarsiers and their extinct relatives, the omomyiforms, i.e. all primates excluding the simi ...

". Under modern classification, the tarsiers and simians are grouped under the suborder

Haplorhini Haplorhini (), the haplorhines (Greek language, Greek for "simple-nosed") or the "dry-nosed" primates is a suborder of primates containing the Tarsiiformes, tarsiers and the simians (Simiiformes or anthropoids), as sister of the Strepsirrhini ("m ...

, while the strepsirrhines are placed in suborder Strepsirrhini. Strong genetic evidence for this is that five

SINEs Sines () is a town and a municipality in Portugal. The municipality, divided into two parishes, has around 14,214 inhabitants (2021) in an area of . Sines holds an important oil refinery and several petrochemical industries. It is also a popular ...

are common to all haplorhines whilst absent in strepsirrhines — even one being coincidental between tarsiers and simians would be quite unlikely. Despite this preferred taxonomic division, "

prosimian Prosimians are a group of primates that includes all living and extinct Strepsirrhini, strepsirrhines (lemurs, Lorisoidea, lorisoids, and Adapiformes, adapiforms), as well as the Haplorhini, haplorhine tarsiers and their extinct relatives, the Om ...

" is still regularly found in textbooks and the academic literature because of familiarity, a condition likened to the use of the

metric system The metric system is a system of measurement that standardization, standardizes a set of base units and a nomenclature for describing relatively large and small quantities via decimal-based multiplicative unit prefixes. Though the rules gover ...

in the sciences and the use of

customary units United States customary units form a system of Units of measurement, measurement units commonly used in the United States and most Territories of the United States, U.S. territories since being standardized and adopted in 1832. The United Stat ...

elsewhere in the United States. In the Anthropoidea, evidence indicates that the Old World and New World primates went through parallel evolution.

Primatology Primatology is the scientific study of non-human primates. It is a diverse discipline at the boundary between mammalogy and anthropology, and researchers can be found in academic departments of anatomy, anthropology, biology, medicine, psychol ...

paleoanthropology Paleoanthropology or paleo-anthropology is a branch of paleontology and anthropology which seeks to understand the early development of anatomically modern humans, a process known as hominization, through the reconstruction of evolutionary kinsh ...

, and other related fields are split on their usage of the synonymous infraorder names, Simiiformes and Anthropoidea. According to

Robert Hoffstetter Robert Julien Hoffstetter (11 June 1908 in Fargniers – 29 December 1999 in Gennevilliers) was a French taxonomist and herpetologist who was influential in categorizing reptiles Reptiles, as commonly defined, are a group of tetrapods with an ...

(and supported by

Colin Groves Colin Peter Groves (24 June 1942 – 30 November 2017) was a British-Australian biologist and anthropologist. Groves was professor of biological anthropology at the Australian National University in Canberra, Australia. Education Born in Englan ...

), the term Simiiformes has priority over Anthropoidea because the taxonomic term ''Simii'' by van der Hoeven, from which it is constructed, dates to 1833. In contrast, Anthropoidea by Mivart dates to 1864, while Simiiformes by

Haeckel Ernst Heinrich Philipp August Haeckel (; ; 16 February 1834 – 9 August 1919) was a German zoologist, naturalist, eugenicist, philosopher, physician, professor, marine biologist and artist. He discovered, described and named thousands of new s ...

dates to 1866, leading to counterclaims of priority. Hoffstetter also argued that Simiiformes is also constructed like a proper infraorder name (ending in "iformes"), whereas Anthropoidea ends in -"oidea", which is reserved for superfamilies. He also noted that Anthropoidea is too easily confused with "anthropoïdes", which translates to "apes" from several languages. Some lines of extinct simian also are either placed into the

Eosimiidae Eosimiidae is the possible family of extinct primates believed to be the earliest simians. Taxonomy When they were discovered, the possibility that eosimiids were outside and ancestral to simians was considered (Culotta 1992), but subsequent ...

(to reflect their

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

origin) and sometimes in

Amphipithecidae The Amphipithecidae were simian primates that lived in Late Eocene and Rupelian, Early Oligocene. Fossils have been found in Myanmar, Thailand, and Pakistan. The limited fossil evidence is consistent with, but not exclusive to, arboreal quadruped ...

, thought to originate in the

Early Oligocene The Rupelian is, in the geologic timescale, the older of two age (geology), ages or the lower of two stage (stratigraphy), stages of the Oligocene epoch (geology), Epoch/series (stratigraphy), Series. It spans the time between . It is preceded b ...

. Additionally, ''

Phileosimias ''Phileosimias'' ("'' Eosimias'' ally") is an extinct genus of primates with two species, ''P. kamli'' and ''P. bahuiorum'', that are believed to be amongst the early simians. Marivaux ''et al.'' announced in 2005 their discovery of fossils of ...

'' is sometimes placed in the Eosimiidae and sometimes categorised separately.

Evolution

The origin of anthropoid primates was initially thought to be Africa, however, fossil evidence now suggests they originated in Asia. During the middle to late

, multiple groups of Asian anthropoids crossed the

Tethys Sea The Tethys Ocean ( ; ), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean during much of the Mesozoic Era and early-mid Cenozoic Era. It was the predecessor to the modern Indian Ocean, the Mediterranean Sea, and the Eurasia ...

on natural rafts or floating islands, colonizing Africa alongside other Asian mammals. The earliest African anthropoid fossils appear in sites across northern Africa, including Algeria, Libya, and Egypt. This dispersal before Africa and Asia were connected by land was aided by size, Asian monsoons, and river systems. After reaching Africa, anthropoids underwent major evolutionary changes, with some groups later crossing the South Atlantic to establish the New World monkey lineage in South America. The New World monkeys in parvorder Platyrrhini 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

and the apes, making Cercopithecidae more closely related to the apes than to the Platyrrhini.

Classification

The following is the listing of the various simian families, and their placement in the order Primates: * Order

Primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...

s ** Suborder

Strepsirrhini Strepsirrhini or Strepsirhini (; ) is a Order (biology), suborder of primates that includes the Lemuriformes, lemuriform primates, which consist of the lemurs of Fauna of Madagascar, Madagascar, galagos ("bushbabies") and pottos from Fauna of A ...

: non

tarsier Tarsiers ( ) are haplorhine primates of the family Tarsiidae, which is the lone extant family within the infraorder Tarsiiformes. Although the group was prehistorically more globally widespread, all of the existing species are restricted to M ...

prosimians ** Suborder

: tarsiers and monkeys, including apes *** Infraorder

Tarsiiformes Tarsiiformes are a group of primates that once ranged across Europe, northern Africa, Asia, and North America, but whose extant species are all found in the islands of Southeast Asia. Tarsiers (family Tarsiidae) are the only living members of ...

***Infraorder Simiiformes **** Parvorder Platyrrhini: New World monkeys ***** Family

Callitrichidae The Callitrichidae (also called Arctopitheci or Hapalidae) are a family of New World monkeys, including marmosets, tamarins, and lion tamarins. At times, this group of animals has been regarded as a subfamily, called the Callitrichinae, of th ...

: marmosets and tamarins ***** Family

Cebidae The Cebidae are one of the five families of New World monkeys now recognised. Extant members are the capuchin and squirrel monkeys. These species are found throughout tropical and subtropical South and Central America. Characteristics Cebid m ...

: capuchins and squirrel monkeys ***** Family

Aotidae Night monkeys, also known as owl monkeys or douroucoulis (), are nocturnal New World monkeys of the genus ''Aotus'', the only member of the family (biology), family Aotidae (). The genus comprises eleven species which are found across Panama an ...

: night or owl monkeys (douroucoulis) ***** Family

Pitheciidae The Pitheciidae () are one of the five families of New World monkeys now recognised. Formerly, they were included in the family Atelidae. The family includes the titis, saki monkeys and uakaris. Most species are native to the Amazon region of ...

: titis, sakis, and uakaris ***** Family

Atelidae The Atelidae are one of the five families of New World monkeys now recognised. It was formerly included in the family Cebidae. Atelids are generally larger monkeys; the family includes the howler, spider, woolly, and woolly spider monkeys (t ...

: howler, spider, and woolly monkeys **** Parvorder

***** Superfamily

Cercopithecoidea Old World monkeys are primates in the family Cercopithecidae (). Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons (genus '' Papio''), red colobus (genus '' Piliocolob ...

: Old World monkeys ****** Family

***** Superfamily

****** Family

Hylobatidae Gibbons () are apes in the Family (biology), family Hylobatidae (). The family historically contained one genus, but now is split into four extant genera and 20 species. Gibbons live in subtropical and tropical forests from eastern Bangladesh an ...

: gibbons ****** Family

Hominidae The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic Family (biology), family of primates that includes eight Neontology#Extant taxa versus extinct taxa, extant species in four Genus, genera: ''Orangutan ...

: great apes, including humans **** †

**** †

**** †'' 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

, not Haplorhini. A 2018 study places Eosimiidae as a sister to the crown haplorhini. In 2020 papers, the

Proteopithecidae Proteopithecidae is an extinct family of primates which lived in the Priabonian (late Eocene) and probably early Oligocene periods. Fossils that have been found are in the Jebel Qatrani Formation in Egypt. Currently two genera are recognised, eac ...

are part of the

Parapithecoidea Parapithecoidea is an extinct superfamily of primates which lived in the Eocene and Oligocene periods in Egypt. In some classifications all Parapithecoidea are placed within the family Parapithecidae. Seiffert ''et al.'' (2010) propose that Parap ...

, and ''

Nosmips aenigmaticus ''Nosmips aenigmaticus'' is a rare fossil primate known only from 12 teeth. Most teeth were found at a site in the Fayum Depression about outside Cairo, Egypt. ''Nosmips aenigmaticus'' probably lived 37 million years ago in Africa and has ...

'' (previously in Eosimidae) is a basal simian. In a 2021 paper, the following basal simians were found: ''Dolichocebus annectens'' and ''Parvimico materdei'' would normally, given their South American location and their age and other factors, be considered Platyrrhini. The original Eosmiidae appear polyphyletic with ''Nosmips,'' ''Bahinia, and'' ''Phileosimias'' at different locations from other eosimians.

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 ou
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 anthropoids 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. Simians characteristically have relatively large brains, fused mandibles, binocular and color vision, and the females have a single fused uterus.Henry R. Hermann Ph.D., in Dominance and Aggression in Humans and Other Animals, 2017 They also have fewer teeth and are more sexually dimorphic in terms of body size and anatomy. The traits that separate New World simians from Old World simians are the nostrils and their dentation. New World simians have broad noses with forward facing nostrils and three premolars in each quadrant of the mouth, while Old World simians have narrower noses with downward facing nostrils and a narrow septum and only have two premolars.

References

External links