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Old World

New World 


Time Tree


An Introduction to Non-human Primates

What makes a primate a primate?

Primates are mammals that climb by grasping.

That was a pretty simple answer to a seemingly complex question.  Don't you think?

Actually, it's not quite that easy.  Some would say that primates are defined as being the one group of mammals that has a bulla made from 
the petrosal bone.  Still seems pretty simple.

Primates are complicated to group and I will give two dueling, popular classifications.  There is one way in which the primates are grouped into Prosimians, Platyrrhini (containing New World Monkeys) and Catarrhini (containing Old World Monkeys and Apes).  The alternative classification is divided into the Strepsirrhini (meaning wet nose) and Haplorrhini (meaning dry nose).  The latter is the new one coming into vogue, but many of us are having a hard time getting rid of the old one; it is more helpful, and I will use the first classifaction throughout this site.

Tarsiers, are the reason for taxonomic dispute.  They have characteristics that place them somewhere in between the prosimians and old world monkeys.  Despite the fact that they have been classified as prosimians for many years, scientists are now reconsidering thier placement. 


Lemurs, lorises, pottos and tarsiers (sometimes!) are included in this group.  They are characterized by behavioral and anatomical traits that more "advanced" primates lack.

1.  Tapetum, a reflective layer in their eyes that allows them to see well at night (see Behavior - nocturnal).
2.  A rhinarium, a wet layer of tissue on their noses that aids in the sense of smell.
3.  Long hind legs for vertical leaping and clinging.
4.  More than two nipple for feeding litters.
5.  Giving birth to multiples.
6.  Sharp pointy teeth with a 2:1:3:3 dentition.
7.  Tooth combs for self grooming (primates usually groom one another as a social function so have no need for this).
8.  Grooming claws (most primates have nails not claws).
9.  Post orbital bar instead of fully inclosed bony eye sockets.

1.  Nocturnal, most primates are diurnal.
2.  Solitary, primates are social animals.


Any monkeys from Central or South America are included in this group.  These monkeys usually retain the "primative" 2:1:3:3 dentition and are generally smaller than old world monkey.  All are arboreal unlike some old world monkeys which are terrestrial.  They are diurnal, eat fruit, have flat incisors, are quadrupeds, vision oriented and have a fully bony eye socket.


Catarrhines are monkeys from Africa and Asia.  They are bigger than old world monkeys, the sit on their rumps (and have rump pads) instead of on their haunches like New World Monkeys, and have cheek pouches.  These cheek pouches are used to quickly gather food when they come to the group and are in danger due to predators.  Some of these monkeys are terrestrial and some are arboreal.  Some of the arboreal ones have sacculated stomachs that aid in the digestion of leaves.  In addition to this, catarrhines have bilophondont molars, otherwise known as four-cusp molars.


Finally, the apes!  Apes have by far the largest brains relative to their body size, with humans having brains four times the size than the human body needs to control normal functions.  Apes have no tails and have five cusp molars.  They have the longest juvenile periods for thier youngs and have fewer offspring per lifetime than other primates.