The New World Monkeys

Do you know the difference between the old world monkeys and the new world monkeys?

Geographic Distribution of the Platyrrhines (New World Monkeys)

They're only found in South America. Fossils go all the way south but species living currently only go a little out of the tropics. They maybe arrived 30 million years ago over the sea somehow- but it was not by a land bridge. Maybe they floated over on something?? Consider the great coincidence of it all- that a mating pair would both end up floating over the ocean at close enough to the same time so they could mate, they found each other, they found a land that was ecologically suited to them but had no other primates on it. This type of immigration is called an adaptive radiation- one species arrives somewhere and then diversifies into many.

Taxonomy of the New World Monkeys

Infraorder Platyrrhini: 3 families, 16 genera
Common features:
Platyrrhini means flat-nosed. New world monkeys' nostrils have a wide septum and they face outward. Old world monkeys have a narrow septum and their nostrils face forwards. New world monkeys are small-to-medium, up to 10 kg. They have 3 premolars while the old world monkeys have 2 premolars. The new world monkeys have a diversity of diets, habits, and social systems.

Family Callitrichidae (marmosets & tamarins)
Taxonomy: 4 genera. The genus saguinus includes the cotton-topped tamarin, the emperor tamarin(named for the emperor of Austria), the jeffries tamarin, the silvery tamarin, and the black-chested mustache tamarin. There's only one species in the genus leontopithicus, and that's the golden lion tamarin. The genus callatric is the common marmoset. The last genus, cebuella, is the pygmy marmoset. They're cute!
Biogeography: Amazon basin, Colombia, Panama
Body size & Anatomy: Small, 'squirrel-like' with long prehensile tails. They're all under 1k. They also redeveloped claws on their fingers except for the hallux. Unusual for primates, they typically have twins. Also, they're decorative; usually colorful and tufty.
Diet: Fruit, insects, gums. Marmosets can be very specialized in eating certain gums.
Society: Facultatively polyandrous or monogamous. They're flexible. Males do a lot of infant care, as well as older siblings. Males in some species carry the young most of the time.

Family Callimiconidae (Goeldi's marmoset)
Taxonomy: A single species, callimico
Biogeography: Amazonia
Body size & Anatomy: Small- less than 1 kg
Diet: Fruit, insects, gums
Society: Apparently polygynous

Family Cebidae
Body size & Anatomy: Generally larger than callitrichids and callimico. They have nails on all digits. They also have long hairy tails, except cacajo, the uakari, which is bald and tail-less.
Subfamily Cebinae
Taxonomy: 2 genera: Cebus (organ-grinder or capuchin monkeys) and saimiri (squirrel monkeys)
Biogeography: Widely distributed in neotropical forests
Body size & anatomy: Small (saimiri = 1 kg) to medium (cebus = 4 kg). Cebus has the largest brain compared to its body size for any new world monkey.
Diet: Frugivore-insectivores, but some will eat anything available.
Society: Multimale-multifemale societies. Squirrel monkeys have a short breeding system and females are dominant.

Subfamily Pithecinae
This is the grab-bag subfamily- has a lot of odds and ends.
Taxonomy: 5 genera: Aotus (night monkey), callicebus (titi), pithecia, chiropotes, and cacajao (uakari), which may be the ugliest new world monkey. They have bright red faces, and are bald.
Biogeography: Pithecia, cacajao (who like to live in flooded forests so haven't been studied too much since they're hard to get to), and chiropotes restricted to Amazonia; Aotus distributed widely; Callicebus dispersed patchily.
Body size & Anatomy: Medium size, 2-4 kg, but aotus and callicebus about 1 kg
Diet: Frugivores, 'seed predators;' uakari eats unripe fruit- really just opens it to get the seeds
Society: Pithecia, cacajao and chiropotes variable; aotus and callicebus monogamous. Aotus (night monkey) is the only nocturnal monkey.

Subfamily Alouttinae
Taxonomy: A single genus alouatta. There are lots of species. These are the howler monkeys. They're pretty common. More often heard than seen.
Biogeography: Found in all regions, they're the most widely dispersed of all the platyrrinni.
Body size & Anatomy: Large (7-8 kg), with an enlarged hyoid bone (in throat) and very deep mandible (related to howling). Long hind gut (related to folivory) because leaves take a long time to digest. Howlers are the analogues of colobinae in old world. Prehensile tails, used for support during feeding.
Diet: Folivorous
Society: Social organization variable, multi-male to single-male groups. Unusual to have such variation within a subfamily. Since they're so common and are easy to identify and slow-moving, they're often studied.

Subfamily Atelinae (wooly monkeys and spider monkeys)
Taxonomy: 3 genera: Ateles (spider monkey), brachyteles (wooly spider monkey aka mariki), and lagothrix (wooly monkey). An interesting physiological fact about these guys: the female's clitoris is bigger than the male's penis! This makes them hard to sex.
Biogeography: Ateles: all areas except SE brazil. Brachyteles: endangered and rare; a few hundred individuals only SE Brazil. Lagothrix: limited to upper Amazon.
Body size & Anatomy: Large; up to 9.5 kg. They are long-limbed, with prehensile tails used in feeding and locomotion (rapid brachiation).
Diet: Frugivorous, but brachyteles folivorous
Society: Ateles has a fission-fusion social system; A group shares a boundary and defends it but they don't usually hang out together. Brachyteles has multimale groups but not much overcompetition, so the females mate with lots of guys. For a male to beat out the others, he just needs to put in more sperm per session, so they have ended up with really big testes. Also there are multifemale groups.