The white-cheeked spider monkey[1] (Ateles marginatus), also known as the white-whiskered spider monkey, is a New World Monkey native to the Amazon Basin of central Brazil.
- Its range is limited by the Xingu River, the Teles Pires River, the Tapajós River, and the Amazon River.
- They live in the highly biodiverse lush lowland rainforests for which the region is known. White-cheeked spider monkeys are primarily black or dark brown, with white fur on their chins, foreheads, and, as their name suggests, cheeks.
- Like all spider monkeys, they have incredibly long legs, arms, and a prehensile tail that helps them swing gently from branches.
- Spider monkey tails have more vertebrae than non-prehensile tails of other primates, and the vertebrae are smaller.
- As a result, the tail is more flexible and extends more than other primates’ tails.
- To help them keep their balance, the underside of their tail is furless and textured like a fingerprint; in fact, their tails are so helpful that they are often called the “fifth limb” or “third hand” of monkeys.
- Unlike most other primates, they do not have an external thumb but instead use their hands as hooks.
- This is actually a peculiar adaptation to their arboreal lifestyle: their ancestors had opposable thumbs, but spider monkeys evolved so that their thumb bones tapered, so they were not visible from the outside.
- Like other spider monkeys, white-cheeked spider monkeys do not exhibit much sexual dimorphism.
