The animals of the order Primates are characterized by certain uniting characteristics, often by increasing either flexibility or sense perception. For instance, all primates have limber shoulders and hip joints to allow a great range of movement. Also, primates have five digits and opposable thumbs and big toes that allow them to grab food or hang on to branches. All of these adaptations were needed for an animal that lived in the trees. The opposable digits help primates hang onto trees, and the shoulders and hip joints provide flexibility for moving around in the trees. Also, the hands of primates are very sensitive, improving their sense of touch, and the eyes are set close together to enhance depth perception. All of the above adaptation make primates the most advanced order in the world. Other uniting characteristics of the primates are the presence of a clavicle, a nail on the first toe, and a large brain. Primates evolved from an arboreal ancestor during the Mesozoic era, and most primates still live in the trees. Humans are the most advanced primates known.

The primates belong to the class Mammalia. They show all of the normal features of mammals, including hair and mammary glands for nursing the young. They are endothermic, have vertebrae and a skeleton, and are segmented deuterosomes, with a coelom made from an outgrowth of the digestive tract. Primates are eutherians, meaning that they have a placenta that provides a more intimate relationship between mother and child while the mother nurses the child. Eutherians are also the mammals with the longest relationship between mother and young. The above features make the animals of the order Primates also eutherians, mammals, vertebrates, and chordates.

There are 13 families in the order Primates. You can click to learn about family Homonidae, the family that humans belong to. Below are the other twelve families, divided into two suborders.

• Family Lemuridae - lemurs
• Family Cheirogaleidae
• Family Indridae - indris
• Family Daubentoniidae
• Family Galagonidae
• Family Loridae - lorises
• Family Megaladapidae

• Family Tarsiidae
• Family Cebidae
• Family Cercopithecidae
• Family Callitrichidae
• Family Hylobatidae-gibbons
• Family Hominidae - humans, chimpanzees, gorillas, orangutans