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Simians Fossil range: Middle Eocene - Recent
Hylobates lar
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Primates Suborder: Haplorrhini Infraorder: Simiiformes Haeckel, 1866
Families
Cebidae Aotidae Pitheciidae Atelidae Cercopithecidae Hylobatidae Hominidae

The simians (infraorder Simiiformes) are the "higher primates" very common to most people: the monkeys and the apes, including humans. Simians tend to be larger than the "lower primates" or prosimians.

Contents 1 Classification 2 Morphological traits defining a simian 3 Simian diversity 4 The first simians 4.1 Time frame 4.2 Different Theories 5 Evolutionary history of the simian subfamily 6 See also 7 References

[edit] Classification

The simians are split into three groups. The first division is literally as wide as the Atlantic Ocean. The New World monkeys in Platyrrhini parvorder split from the simian line about 40 million years ago (mya), leaving the Catarrhini parvorder occupying the Old World. This group split about 25 mya between the Old World monkeys and the apes. Earlier classifications split the primates into two large groups: the "Prosimii" (strepsirrhines and tarsiers) and the simians in "Anthropoidea"(an'thro-poy'de-a)(Gr. anthropos, man).

• ORDER PRIMATES
  • Suborder Strepsirrhini: non-tarsier prosimians
  • Suborder Haplorrhini: tarsiers, monkeys and apes
    • Infraorder Tarsiiformes
    • Infraorder Simiiformes
      • Parvorder Platyrrhini: New World monkeys
        • Family Cebidae: marmosets, tamarins, capuchins and squirrel monkeys
        • Family Aotidae: night or owl monkeys (douroucoulis)
        • Family Pitheciidae: titis, sakis and uakaris
        • Family Atelidae: howler, spider and woolly monkeys
      • Parvorder Catarrhini
        • Superfamily Cercopithecoidea
          • Family Cercopithecidae: Old World monkeys
        • Superfamily Hominoidea
          • Family Hylobatidae: gibbons
          • Family Hominidae: great apes and humans

[edit] Morphological traits defining a simian

Most simians are diurnal and the family overall is larger than both prosimians and tarsiers. Cranially, they have a reduced snout, an increased reliance upon vision, a reduced tapetum lucidum, relatively larger braincases, and a postorbital plate. Dentally, all anthropoids have two incisors, one canine, two or three premolars, and three molars.

However, there is no one trait except perhaps complete postorbital closure that definitively classifies a species as prosimian or simian. There is a great deal of variation in traits among different families of anthropoids. Most simians display many but not all of the above traits. Simians on the whole are also less derived than either Tarsiiformes or Prosimii, meaning many traits held by simians as a group were also probably held by the last common ancestor between Tarsiers and Simians or even the last common ancestor of Haplorrhines and Strepsirrhines, and are therefore not distinguishing.

[edit] Simian diversity

[edit] The first simians

[edit] Time frame

[edit] Different Theories

[edit] Evolutionary history of the simian subfamily

[edit] See also

• Simia, Carolus Linnaeus's original classification of these primates.

[edit] References

• Groves, Colin (16 November 2005). in Wilson, D. E., and Reeder, D. M. (eds): Mammal Species of the World, 3rd edition, Johns Hopkins University Press, 128-184. ISBN 0-801-88221-4.