Old World Monkeys vs. New World Monkeys: 7 Key Differences

When you think of a monkey, you probably picture a furry animal with long arms swinging through trees. Monkey taxonomy (classification) is a lot more complicated than that. Monkeys are a type of primate; despite some basic similarities, they are a diverse group of animals. They can be categorized into two families: the Old World monkeys and the New World monkeys. These two groups of monkeys have evolved independently for at least 30 million years, so it’s no wonder they are no longer the same. Here, we examine the seven key differences between Old World and New World monkeys.

What Are Old World Monkeys?

The scientific name for ‘Old World monkeys’ is cercopithecids, part of the infraorder Catarrhini. They can be further divided into two subfamilies – the cercopithecines (which have check pouches) and the colonies (leaf-eating monkeys). Baboons, mandrills, macaques, rhesus monkeys, and proboscis monkeys are all Old World monkeys.

What Are New World Monkeys?

 The ‘New World monkey’ group includes five primate families: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae, and are in the parvorder Platyrrhini. There are more than 16 New World monkey species, including gracile capuchin, owl, howler, and saddle-back tamarin.

Old World Monkeys vs New World Monkeys: 7 Key Differences

1. Geographic Location

As you would expect, Old World monkeys live in what is referred to as the ‘Old World,’ comprising Europe, Africa, and Asia. New World monkeys live in the ‘New World,’ which is the Americas. However, their range is limited to the tropical forests of southern Mexico and Central and South America.

2. Preferred Habitat

Nearly all New World monkeys are arboreal, meaning they are tree–dwellers found in rainforests. In contrast, Old World monkeys spend much more time on the ground. While a few species of Old World monkeys live in rainforests and climb trees, many more live in savannahs and mountainous regions.

3. Tail Anatomy

Most monkeys have tails, but they are used very differently by the two groups. New World monkeys often have a longer and prehensile tail. This means that it has adapted to grasp hold of objects. It is a common feature in arboreal (tree-living) animals because it helps to stop them from falling out of trees! In contrast, the Old World monkeys spend more time on the ground and do not need this type of tail. Their tail is non-prehensile, shorter, and cannot be used to grip anything.

4. Padded Buttocks

Old World monkeys have pads of thickened tissue (calloused skin) called ischial callosities. They cover the part of the hip bones that they sit on. This is essentially their buttocks and makes it more comfortable to sit down when feeding or resting. New World monkeys do not sit down so often (and sleep in trees), so they don’t have them.

5. Nose Shape

Old and New World monkeys have different face and nose shapes. New World monkeys rely more on their eyesight than their sense of smell, so their noses are shorter without the moist rhinarium (the hairless area around the nostrils that helps with scent). The nostrils are widely separated (there is a wide septum) and point sideways. Their eyes face forward, giving a larger region of overlapping vision, and they are better at moving their faces and communicating with facial expressions. Old World monkeys, on the other hand, have nostrils that are closer together (narrow septum) and point forward or downward.

6. Opposable Thumbs

The Old World monkeys have hands very like our own. They have opposable thumbs that can be moved freely and independently. They also have fingernails rather than claws. In comparison, only a few New World monkeys have opposable thumbs, including the tamarin and the capuchin monkeys.

7. Teeth

The layout of teeth does not vary significantly amongst the primates. They all have two incisors at the front of the mouth for biting off food. Then, there are canines behind those for piercing and tearing. Behind these are varying numbers of premolars and molars used to grind more fibrous food. New World monkeys have three premolars, usually two but occasionally three molars. In contrast, Old World monkeys always have two premolars and three molars. They share this dental arrangement with apes and humans.

Other Differences Between Old World and New World Monkeys

Some other differences between these two types of monkeys are generalizations and do not apply to every monkey. In general, Old World Monkeys are more significant than New World Monkeys. Also, they are herbivorous or omnivorous, whereas New World Monkeys tend to be frugivorous or insectivorous. Old World Monkeys tend to have a more extended gestation period.

Summary of old-world monkeys vs new-world monkeys

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