Primates
From Palaeos
The order 'Primates contains the lemurs, monkeys, apes and allies, as well as us - humans. Primates are found all over the world. Non-human primates occur mostly in Central and South America, Africa, and southern Asia. A few species exist as far north in the Americas as southern Mexico, and as far north in Asia as northern Japan.
The order Primates was established by Linnaeus in 1758, in the tenth edition of his book Systema Naturae for the genera Homo (humans), Simia (other apes and monkeys), Lemur (prosimians) and Vespertilio (bats). In following editions, he also suggested that non-primate mammals should be called Secundates and that non-mammal animals should be called Tertiates, neither of which was accepted. In the first edition (1735), he had used the taxon Anthropomorpha for Homo, Simia and Bradypus (sloths). The Latin primates, the plural of nominative singular primas, means "one of the first, excellent, noble".
The Primates order is divided informally into three main groupings: prosimians, monkeys of the New World, and monkeys and apes of the Old World. The prosimians are species whose bodies most closely resemble that of the early proto-primates. The most well known of the prosimians, the lemurs, are located on the island of Madagascar and to a lesser extent on the Comoros Islands, isolated from the rest of the world. The New World monkeys include the familiar capuchin, howler and squirrel monkeys. They live exclusively in the Americas. Discounting humans, the rest of the simians, the Old World monkeys and the apes, inhabit Africa and southern and central Asia, although fossil evidence shows many species existed in Europe as well.
Primates have been described from the latest Cretaceous based on the genus Purgatorius, though this genus is now regarded as dating from the Palaeocene and may not be related to Primates (Wible et al., 2007). Molecular clock studies suggest that the primate branch is even more ancient (originating at least in the mid-Cretaceous). They are now thought to be most closely related to flying lemurs and, more distantly, to treeshrews. They probably have descended from Plesiadapiformes.
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Physical description
Shortened rostrum; addition of hypocone & loss of paraconid from basic tribosphenic pattern; bunodont cusps; loss of at least 1 incisor and 1 premolar in all but most basal forms; orbits face anteriorly, with stereoscopic vision & well-developed vision; ethmoid exposed on orbital wall; postorbital bar; enlarged brain; floor of auditory bulla from petrosal; clavicle retained as prominent element of pectoral girdle; shoulder joint with broad mobility; digits 5/5; opposable digits; tactile pads at ends of digits; elongated hind limb; facultative bipedalism common; nail on hallux and other digits; herbivorous or omnivorous; 2 mammaries; 1-2 young per pregnancy; long gestation and developmental time; frequently highly social, with flexible dominance hierarchies; strongly adapted to arboreal life.
Comments
All primates have five fingers (pentadactyly), a generalized dental pattern, and a primitive (unspecialized) body plan. Another distinguishing feature of primates is fingernails. Opposing thumbs are also a characteristic primate feature, but are not limited to this order; opossums, for example, also have opposing thumbs. In primates, the combination of opposing thumbs, short fingernails (rather than claws) and long, inward-closing fingers is a relic of the ancestral practice of gripping branches, and has, in part, allowed some species to develop brachiation as a significant means of transportation. Forward-facing color binocular vision was also useful for the brachiating ancestors of humans, particularly for finding and collecting food, although recent studies suggest it was more useful in courtship. All primates, even those that lack the features typical of other primates (like lorises), share eye orbit characteristics, such as a postorbital bar, that distinguish them from other taxonomic orders.
Old World species (apes and some monkeys) tend to have significant sexual dimorphism. This is characterized most in size difference, with males being slightly more than twice as heavy as females. This dimorphism may be a result of a polygynous mating system where there is significant pressure to attract and defend multiple females. New World species form pair bonds, and so these species (including tamarins and marmosets) generally do not show a significant size difference between the sexes.
Habitat
Primates evolved from arboreal animals and many modern species live mostly in trees and hardly ever come to the ground. Other species are partially terrestrial, such as baboons and the patas monkey. Only a few species are fully terrestrial, such as the gelada and humans. Primates live in a diverse number of forested habitats, including rain forests, mangrove forests, and mountain forests to altitudes of over 3000 m. Although most species are generally shy of water, a few are fine swimmers and are comfortable in swamps and watery areas, including the proboscis monkey, De Brazza's monkey and Allen's swamp monkey, which even developed small webbing between its fingers. Some primates, such the rhesus macaque and the Hanuman langur, can exploit human-modified environments and even live in cities.
Classification and evolution
Close relations
The Primates lie in a tight clustering of related orders (the Euarchontoglires) within the Eutheria, a subclass of Mammalia. Recent molecular genetic research on primates, flying lemurs, and treeshrews has shown that the two species of flying lemur (Dermoptera) are more closely related to the primates than the treeshrews of the order Scandentia, even though the treeshrews were at one time considered primates. These three orders make up the Euarchonta clade. This clade combines with the Glires clade (made up of the Rodentia and Lagomorpha) to form the Euarchontoglires clade. Variously, both Euarchonta and Euarchontoglires are ranked as superorders. Also, some scientists consider Dermoptera a suborder of Primates and call the "true" primates the suborder Euprimates (Hoffstetter, 1978).
Classification
In older classifications, the Primates were divided into two superfamilies: Prosimii and Anthropoidea. The Prosimii included all of the prosimians: all of Strepsirrhini plus the tarsiers. The Anthropoidea contained all of the simians.
In modern, cladistic reckonings, the Primates is also a true clade. The suborder Strepsirrhini, the "wet-nosed" primates, split off from the primitive primate line about 63 million years ago (mya). The seven strepsirhine families are the four related lemur families and the three remaining families that include the lorises, the aye-aye, the galagos, and the pottos (Groves, 2005). Older classification schemes wrap the Lepilemuridae into the Lemuridae and the Galagidae into the Lorisidae, yielding a three-two family split instead of the four-three split as presented here. Other lineages of lower primates inhabited Earth. During the Eocene, most of the northern continents were dominated by two dominant groups, the adapids and the omomyids. The former is considered a member of Strepsirrhini, but it does not have a tooth-comb like modern lemurs. The latter was related closely to tarsiers, monkeys, and apes. Adapids survived until 10 mya; omomyids on the other hand perished 20 million years earlier.
The aye-aye is difficult to place in Strepsirrhini. Its family, Daubentoniidae, could be a lemuriform primate and its ancestors split from lemur line more recently than the lemurs and lorises split, about 50 mya. Otherwise it is sister to all of the other strepsirrhines, in which case in evolved away from the main strepsirrhine line between 50 and 63 mya.
The suborder Haplorrhini, the "dry-nosed" primates, is composed of two sister clades (Groves, 2005). The prosimian tarsiers in family Tarsiidae (monotypic in its own infraorder Tarsiiformes) represent the most primitive division at about 58 mya. The infraorder Simiiformes contains two parvorders, the New World monkeys in one, and the Old World monkeys, humans and the other apes in the other (Groves, 2005). This division happened about 40 mya. However about 30 mya, three groups split from the main haplorrhine lineage. One group stayed in Asia and are closest in kin to the "dawn monkey" Eosimias. The second stayed in Africa, where they developed into the Old World primates. The third rafted to South America to become the New World monkeys. Mysteriously the aboriginal Asian Haplorrhini vanished from record once Africa collided with Eurasia 24 mya. Apes and monkeys spread into Europe and Asia. Close behind came lorises and tarsiers, also African castaways. The first hominid fossils were discovered in Northern Africa and date back 7 mya. Modern humans did not appear until 0.2 mya, eventually becoming the most prevalent primate and mammal on Earth.
The discovery of new species happens at a rate of a few new species each year, and the evaluation of current populations as distinct species is in flux. Colin Groves listed about 350 species of primates in Primate Taxonomy in 2001. The recently published third edition of Mammal Species of the World lists 376 species (Groves, 2005). But even Groves' (2005) list falls short of current understanding as its collection cutoff was in 2003, and a number publications since then have pushed the number of species up to 405. Notable new species not listed in Groves (2005) include the Bemaraha Woolly Lemur (Avahi cleesei) (named after British actor and lemur enthusiast John Cleese) and the GoldenPalace.com Monkey (whose name was put up for auction).
Extant primate families
* ORDER PRIMATES
o Suborder Strepsirrhini: non-tarsier prosimians
+ Infraorder Lemuriformes
# Superfamily Cheirogaleoidea
* Family Cheirogaleidae: dwarf lemurs and mouse-lemurs (30 species)
# Superfamily Lemuroidea
* Family Lemuridae: lemurs (19 species)
* Family Lepilemuridae: sportive lemurs (22 species)
* Family Indriidae: woolly lemurs and allies (14 species)
+ Infraorder Chiromyiformes
# Family Daubentoniidae: Aye-aye (1 species)
+ Infraorder Lorisiformes
# Family Lorisidae: lorises, pottos and allies (9 species)
# Family Galagidae: galagos (19 species)
o Suborder Haplorrhini: tarsiers, monkeys and apes
+ Infraorder Tarsiiformes
# Family Tarsiidae: tarsiers (8 species)
+ Infraorder Simiiformes
# Parvorder Platyrrhini: New World monkeys
* Family Cebidae: marmosets, tamarins, capuchins and squirrel monkeys (56 species)
* Family Aotidae: night or owl monkeys (douroucoulis) (7 species)
* Family Pitheciidae: titis, sakis and uakaris (41 species)
* Family Atelidae: howler, spider and woolly monkeys (24 species)
# Parvorder Catarrhini
* Superfamily Cercopithecoidea
o Family Cercopithecidae: Old World monkeys (135 species)
* Superfamily Hominoidea
o Family Hylobatidae: gibbons or "lesser apes" (13 species)
o Family Hominidae: humans and other great apes (7 species)
Some prehistoric primates
* Adapis, an adapid * Aegyptopithecus zeuxis, an early haplorrhine * Australopithecus, ape-like human ancestor * Branisella boliviana, an early New World monkey * Dryopithecus, an early ape * Eosimias, an early catarrhine * Gigantopithecus, the largest ape * Godinotia, an adapid * Megaladapis, a giant lemur * Notharctus, an adapid * Pierolapithecus catalaunicus, a possible ancestor of large apes * Plesiopithecus teras, a relative of lorises and galagos * Pliopithecus, ancestor of the modern gibbons * Protopithecus brasiliensis, a giant New World monkey * Sahelanthropus tchadensis, a possible ancestor of humans * Sivapithecus, an early ape * Tielhardina, the earliest haplorrhines * Victoriapithecus, an early Old World monkey
See also
References
Groves. C. 2001. Primate Taxonomy. Smithsonian Institute Press. ISBN 1-56098-872-X.
Groves, C. 2005. In Mammal Species of the World, 3rd edition (D. E. Wilson & D. M. Reeder, eds.) pp. 111-184. Johns Hopkins University Press. ISBN 0-801-88221-4.
Wible, J.R., G.W. Rougier, M.J. Novacek & R.J. Asher. 2007. Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary. Nature 447:1003-1006.
Credits
Physical description from Palaeos.com
