Within the Parvorder Catarrhini, there are two superfamilies: Cercopithecoidea (the Old World monkeys) and Hominoidea (apes and humans). A number of traits can be used to distinguish them:

Within the Cercopithecoidea (Old World monkeys), there is a further division between two subfamilies: the Colobinae (leaf-eating monkeys) and the Cercopithecinae (omnivorous monkeys). These groups, too, can be distinguished by a number of characteristics:

Note: a callosity is a callus, like the callus that we develop on the bottom of our feet, where the skin thickens due to repeated friction. An ischial callosity is a callus that develops above the ischium, the portion of the pelvis that we sit on. In other words, an ischial callosity is a butt callus. They protect parts of the animals anatomy that come into frequent contact with the ground or rough tree bark, and they allow monkeys to sit comfortably in trees for long periods. They also swell and turn red to show when a female is fertile.

Subfamily Colobinae (Leaf-eating Monkeys)

Colobinae are specialized leaf-eaters. Most groups of colobine monkeys live in Asia (such as the langurs, the proboscis monkey, and the snub-nosed monkey), but the colobus monkey of Africa also belongs in this group. The colobus is found throughout tropical Africa, while langurs and other Asian colobine monkeys are found from India through Indonesia.

Locomotion: Colobinae are quadrupedal.

Social Organization: The social organization of the Colobinae is variable. Some colobus monkeys have family groups with one male and a "harem" of females. Others colobus monkeys and langurs live in large multimale/multifemale groups, with dominance hierarchies. Some, like the pig-tailed langurs, are monogamous.

Active time: Like most Haplorhini primates, they are diurnal

Habitat: Colobinae live in a wide range of habitats, from high mountains to swamps to bamboo forests to tropical rainforests. Colobus monkeys are found in tropical and mountain forests. The Asian species are more variable in their habitats. Langurs, considered a sacred monkey in India, frequently live in towns. Some Colobinae are completely arboreal. The appropriately-named proboscis monkey, for example, spends almost no time on the ground. Other Colobinae are mostly terrestrial, spending very little time in the trees. Some species of langurs, for example, spend the majority of their time on the ground.

Diet: They eat leaves, hence the name "Leaf-eating Monkeys". They do spice up their diet with fruit, but their stomachs are specially adapted to eat a high-fiber leafy diet.

Subfamily Cercopithecinae

Cercopithecinae monkeys are highly diverse. Most live in sub-Saharan Africa, but the macaques are wide-spread from Northern Africa through Japan. Unlike the Colobinae, which are specialized leaf-eaters, the Cercopithecinae are omnivores, and represent a wider range of adaptations. Some of the species found within this subfamily are the mangabeys, baboons, mandrills and drills, and macaques.

Locomotion: Cercopithecinae monkeys are quadrupedal. Some, like this patas monkey, can be quite fast.

Social Organization: Types of social organization are highly variable within the Cercopithecinae. Many species have multimale/multifemale groups with strong dominance hierarchies. This is found in macaques, baboons, and drills, for example. Some groups form single-male groups with a female "harem". This is seen in some mangabeys, some baboons, and the patas monkey. Others, like talapoins, have large groups without very strong dominance hierarchies, more like the New World monkeys. There is no one rule for Cercopithecinae social organization.

Active time: Like most Haplorhini, the Cercopithecinae are diurnal

Habitat: In habitat, as in social organization, the Cercopithecinae are highly variable. Some, like the mangabeys, are only found in rainforests. Others, like baboons, are found in open savannah areas as well as forests. Macaques are found almost everywhere, from forests to towns to natural hot-springs saunas. Most Cercopithecinae spend more time on the ground than the Colobinae do, but this is only a generalization. Some species, like the baboons, live almost entirely on land. Others, like the mangabey, live almost entirely in trees.

Diet: omnivorous and extremely varied. None of the Cercopithecinae eat significant amounts of meat, however.