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 Ceboidea , the only extant superfamily in the parvorder Platyrrhini .
Platyrrhini means broad-nosed, and their noses are flatter than those of other simians, with sideways-facing nostrils.
Monkeys in the family Atelidae, such as the spider monkey, are the only primates to have prehensile tails.
New World monkeys' closest relatives are the other simians, the Catarrhini ("down-nosed"), comprising Old World monkeys and apes.
New World monkeys descend from African simians that colonized South America, a line that split off about 40 million years ago.
Evolutionary history
About 40 million years ago, the Simiiformes infraorder split into the parvorders Platyrrhini (New World monkeys—in South America) and Catarrhini (apes and Old World monkeys—in Africa).
The individuals whose descendants would become Platyrrhini are currently conjectured to have migrated to South America either on a raft of vegetation or via a land bridge.
There are two possible rafting routes, either across the Atlantic Ocean from Africa or across the Caribbean from North America; however, there is no fossil record to support the hypothesis of a migration from North America.
The land bridge hypothesis relies on the existence of Atlantic Ocean ridges and a fall in the sea level in the Oligocene.
This would have produced either a single land bridge or a series of mid-Atlantic islands to act as stepping stones for the migration.
The latter is now the favoured land bridge hypothesis.Alan de Queiroz, The Monkey's Voyage, Basic Books, 2014.
At the time the New World monkeys split off, the Isthmus of Panama had not yet formed, ocean currents and climate were quite different, and the Atlantic Ocean was less than the present  width by about a third; possibly  less, based on the current estimate of the Atlantic mid-ocean ridge formation processes spreading rate of .
However, the Ucayalipithecus of Amazonian Peru who might have rafted across the Atlantic between ~35–32 million years ago, are nested within the Parapithecoidea from the Eocene of Afro-Arabia.
The chromosomal content of the ancestor species appears to have been 2n = 54.de Oliveira EH, Neusser M, Müller S (2012) Chromosome evolution in New World Monkeys (Platyrrhini).
Cytogenet Genome Res In extant species, the 2n value varies from 16 in the titi monkey to 62 in the woolly monkey.
A Bayesian estimate of the most recent common ancestor of the extant species has a 95% credible interval of -.Perez SI, Tejedor MF, Novo NM, Aristide L (2013) "Divergence times and the evolutionary radiation of New World monkeys (Platyrrhini, Primates): An analysis of fossil and molecular Data".
PLoS One 8(6):e68029.
Classification
The following is the listing of the various platyrrhine families, as defined by Ryland & Mittermeier (2009), and their position in the Order Primates:
Order Primates
Suborder Strepsirrhini: lemurs, lorises, galagos, etc.
Suborder Haplorrhini: tarsiers + monkeys, including apes
Infraorder Tarsiiformes: tarsiers
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, woolly spider, and woolly monkeys
Parvorder Catarrhini: Old World monkeys, apes, and humans
Characteristics
New World monkeys are small to mid-sized primates, ranging from the pygmy marmoset (the world's smallest monkey), at  and a weight of , to the southern muriqui, at  and a weight of .
New World monkeys differ slightly from Old World monkeys in several aspects.
The most prominent phenotypic distinction is the nose, which is the feature used most commonly to distinguish between the two groups.
The clade for the New World monkeys, Platyrrhini, means "flat nosed".
The noses of New World monkeys are flatter than the narrow noses of the Old World monkeys, and have side-facing nostrils.
New World monkeys are the only monkeys with prehensile tails—in comparison with the shorter, non-grasping tails of the anthropoids of the Old World.
Prehensility has evolved at least two distinct times in platyrrhines, in the Atelidae family (spider monkeys, wooly spider monkeys, howler monkeys, and wooly monkeys), and in capuchin monkeys (Cebus).
Although prehensility is present in all of these primate species, skeletal and muscular-based morphological differences between these two groups indicate that the trait evolved separately through convergent evolution.
The fully prehensile tails that have evolved in Atelidae allow the primates to suspend their entire body weight by only their tails, with arms and legs free for other foraging and locomotive activities.
Semi-prehensile tails in Cebus can be used for balance by wrapping the tail around branches and supporting a large portion of their weight.
New World monkeys (except for the howler monkeys of genus Alouatta) also typically lack the trichromatic vision of Old World monkeys.
Colour vision in New World primates relies on a single gene on the X-chromosome to produce pigments that absorb medium and long wavelength light, which contrasts with short wavelength light.
As a result, males rely on a single medium/long pigment gene and are dichromatic, as are homozygous females.
Heterozygous females may possess two alleles with different sensitivities within this range, and so can display trichromatic vision.
Platyrrhines also differ from Old World monkeys in that they have twelve premolars instead of eight; having a dental formula of  or  (consisting of 2 incisors, 1 canine, 3 premolars, and 2 or 3 molars).
This is in contrast with Old World Anthropoids, including gorillas, chimpanzees, bonobos, siamangs, gibbons, orangutans, and most humans, which share a dental formula of .
Many New World monkeys are small and almost all are arboreal, so knowledge of them is less comprehensive than that of the more easily observed Old World monkeys.
Unlike most Old World monkeys, many New World monkeys form monogamous pair bonds, and show substantial paternal care of young.New World Monkeys at Animal Corner They eat fruits, nuts, insects, flowers, bird eggs, spiders, and small mammals.
Unlike humans and most Old World monkeys, their thumbs are not opposable (except for some Cebids).
See also
List of New World monkey species
List of primates by population
References
Further reading
External links
Geographic Distributions of Amazonian Primates – Tomas and Marc van Roosmalen, Pdf 3,2 Mb
