The simians are the "higher primate

Primate

A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...

s" familiar to most people: the Old World monkey

Old World monkey

The Old World monkeys or Cercopithecidae are a group of primates, falling in the superfamily Cercopithecoidea in the clade Catarrhini. The Old World monkeys are native to Africa and Asia today, inhabiting a range of environments from tropical rain forest to savanna, shrubland and mountainous...

s and ape

Ape

Apes are Old World anthropoid mammals, more specifically a clade of tailless catarrhine primates, belonging to the biological superfamily Hominoidea. The apes are native to Africa and South-east Asia, although in relatively recent times humans have spread all over the world...

s, including humans, (together being the catarrhines), and the New World monkey

New World monkey

New World monkeys are the five families of primates that are found in Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Platyrrhini parvorder and the Ceboidea superfamily, which are essentially synonymous since...

s or platyrrhines. Simians tend to be larger than the "lower primates" or prosimian

Prosimian

Prosimians are a grouping of mammals defined as being primates, but not monkeys or apes. They include, among others, lemurs, bushbabies, and tarsiers. They are considered to have characteristics that are more primitive than those of monkeys and apes. Prosimians are the only primates native to...

s.

Classification and evolution

The simians are split into three groups. The New World monkey

New World monkey

New World monkeys are the five families of primates that are found in Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Platyrrhini parvorder and the Ceboidea superfamily, which are essentially synonymous since...

s in parvorder Platyrrhini split from the rest of the simian line about 40 million years ago (mya), leaving the parvorder Catarrhini

Catarrhini

Catarrhini is one of the two subdivisions of the higher primates . It contains the Old World monkeys and the apes, which in turn are further divided into the lesser apes or gibbons and the great apes, consisting of the orangutans, gorillas, chimpanzees, bonobos, and humans...

 occupying the Old World. This group split about 25 mya between the Old World monkeys and the apes. "Monkey

Monkey

A monkey is a primate, either an Old World monkey or a New World monkey. There are about 260 known living species of monkey. Many are arboreal, although there are species that live primarily on the ground, such as baboons. Monkeys are generally considered to be intelligent. Unlike apes, monkeys...

s" are a paraphyletic group (i.e. not a single coherent group). Earlier classifications split the primates into two large groups: the "Prosimii" (strepsirrhines and tarsier

Tarsier

Tarsiers are haplorrhine primates of the genus Tarsius, a genus in the family Tarsiidae, which is itself the lone extant family within the infraorder Tarsiiformes...

s) and the simians in "Anthropoidea" /an'thro-poy'de-a/ (Gr. anthropos, human).

The following is the listing of the various simian families, and their placement in the order Primates:

• ORDER PRIMATES
  Primate
  A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
  
  
  • Suborder Strepsirrhini
    Strepsirrhini
    The clade Strepsirrhini is one of the two suborders of primates. Madagascar's only non-human primates are strepsirrhines, and others can be found in southeast Asia and Africa...
    
    : non-tarsier
    Tarsier
    Tarsiers are haplorrhine primates of the genus Tarsius, a genus in the family Tarsiidae, which is itself the lone extant family within the infraorder Tarsiiformes...
    
     prosimians
  • Suborder Haplorrhini
    Haplorrhini
    The haplorhines, the "dry-nosed" primates , are members of the Haplorhini clade: the prosimian tarsiers and the anthropoids...
    
    : tarsiers, monkeys and apes
    • Infraorder Tarsiiformes
      Tarsiiformes
      Tarsiiformes are a group of primates that was once ranged across Europe, northern Africa, Asia, and North America, but today all living species are found in the islands of Southeast Asia. Tarsiers are the only living members of the infraorder, and also include the extinct Tarsius eocaenus from the...
      
      
    • Infraorder Simiiformes
      • Parvorder Platyrrhini: New World monkeys
        • Family Callitrichidae: marmosets and tamarins
        • Family Cebidae
          Cebidae
          The Cebidae is one of the five families of New World monkeys now recognised. It includes the capuchin monkeys and squirrel monkeys. These species are found throughout tropical and subtropical South and Central America.-Characteristics:...
          
          : capuchins and squirrel monkeys
        • Family Aotidae: night or owl monkeys (douroucoulis)
        • Family Pitheciidae
          Pitheciidae
          The Pitheciidae are one of the five families of New World monkeys now recognised. Formerly they were included in the family Atelidae. The family includes the titis, saki monkeys and uakaris...
          
          : titis, sakis and uakaris
        • Family Atelidae
          Atelidae
          Atelidae is one of the five families of New World monkeys now recognised. It was formerly included in the family Cebidae. Atelids are generally larger monkeys; the family includes the howler, spider, woolly and woolly spider monkeys...
          
          : howler, spider and woolly monkeys
      • Parvorder Catarrhini
        Catarrhini
        Catarrhini is one of the two subdivisions of the higher primates . It contains the Old World monkeys and the apes, which in turn are further divided into the lesser apes or gibbons and the great apes, consisting of the orangutans, gorillas, chimpanzees, bonobos, and humans...
        
        
        • Superfamily Cercopithecoidea
          Old World monkey
          The Old World monkeys or Cercopithecidae are a group of primates, falling in the superfamily Cercopithecoidea in the clade Catarrhini. The Old World monkeys are native to Africa and Asia today, inhabiting a range of environments from tropical rain forest to savanna, shrubland and mountainous...
          
          
          • Family Cercopithecidae
            Old World monkey
            The Old World monkeys or Cercopithecidae are a group of primates, falling in the superfamily Cercopithecoidea in the clade Catarrhini. The Old World monkeys are native to Africa and Asia today, inhabiting a range of environments from tropical rain forest to savanna, shrubland and mountainous...
            
            : Old World monkeys
        • Superfamily Hominoidea
          • Family Hylobatidae: gibbons
          • Family Hominidae
            Hominidae
            The Hominidae or include them .), as the term is used here, form a taxonomic family, including four extant genera: chimpanzees , gorillas , humans , and orangutans ....
            
            : great apes, including humans