A nail on the first digit although, in many cases, each digit has a nail instead of a claw.
The order Primates includes humans, apes, monkeys, and prosimians. Many of them may be familiar, but it would not be surprising if you cannot immediately visualize prosimians (like the ring-tailed lemurs in the picture on the right) . How many living primate species exist today is not clear.  Considered generalist mammals, primates exhibit a wide range of characteristics. Some primates (including some great apes and baboons) are primarily terrestrial rather than arboreal, but all species possess adaptations for climbing trees. The order Primates was traditionally divided into two main groupings: prosimians and anthropoids (simians). Prosimians have characteristics more like those of the earliest primates, and include the lemurs of Madagascar, lorisoids, and tarsiers. Prosimians retain relatively primitive primate characteristics. Unlike simians (monkeys, apes and hominids), prosimians' brains are not exceptionally large compared to other mammals. Most have wet, dog-like noses, except for tarsiers. Tarsiers in fact are more closely related to simians than to the other prosimians. They are primitive in the sense that they retain characteristics of the very first primates from millions of years ago. Prosimians include lemurs, lorises, galagos and tarsiers. Within simians, the next most primitive group is the new world monkeys. There are more 300 species of primates in the worldfrom humans and apes to monkeys and prosimians (premonkeys). Several primate species have been discovered in Brazil and Madagascar in recent years. The smallest primate is the pygmy mouse lemur, which can fit in the palm of your hand. About Primates.  A primate (/ˈpraɪmeɪt/ PRY-mayt) is a mammal of the order Primates (/praɪˈmeɪtiːz/ pry-MAY-teez; Latin : prime, first rank). In taxonomy, primates include two distinct lineages, strepsirrhines and haplorhines. The order Primates was traditionally divided into two main groupings: prosimians and anthropoids (simians). Prosimians have characteristics more like those of the earliest primates, and include the lemurs of Madagascar, lorisoids, and tarsiers. Primates are an extremely diverse group of between 190 and 350 living species, depending on different taxonomic structures, and exhibit a wide range of characteristic features that help distinguish them from other mammals. They range in size from the 2-ounce pygmy mouse lemur to the 440-pound wild gorilla. Other Characteristics. Other primate characteristics include having a nail on the first digit although, in many cases, each digit has a nail instead of a claw. Primates also possess a clavicle, or collarbone. All primates exhibit the tendency to be erect; this trait is visible when even quadrapedal primates sit or stand Brain. The brains of primates often is one of the most distinguishable characteristics from other types of mammals or animals. The olfactory region in primates has been reduced greatly in most species, such as humans, and the cerebrum expanded to accept the order's increasing reliance on sight and social behaviors. Other Characteristics. Other primate characteristics include having a nail on the first digit although, in many cases, each digit has a nail instead of a claw. Primates also possess a clavicle, or collarbone. All primates exhibit the tendency to be erect; this trait is visible when even quadrapedal primates sit or stand The most primitive living primates are called prosimians. They are primitive in the sense that they retain characteristics of the very first primates from millions of years ago. Prosimians include lemurs, lorises, galagos and tarsiers. Within simians, the next most primitive group is the new world monkeys. These monkeys are native to North and South America Some characteristics of primates include their hairy bodies,  intelligence, and long limbs. They are the closest genetic relative  to humans in the animal kingdom. 
http://anthro.palomar.edu/primate/prim_1.htm https://en.wikipedia.org/wiki/Primate http://study.com/academy/lesson/primates-definition-evolution-characteristics.html http://nationalzoo.si.edu/Animals/Primates/Facts/default.cfm https://en.wikipedia.org/wiki/Primate http://animals.mom.me/major-characteristics-primates-3721.html http://animals.mom.me/major-characteristics-primates-3721.html http://study.com/academy/lesson/primates-definition-evolution-characteristics.html http://www.answers.com/Q/What_characteristics_do_primates_have
what are the characteristics of primates