Simian - Classification and Evolution

Classification and Evolution

In earlier classification, New World monkeys, Old World monkeys, apes, and humans—collectively known as simians or anthropoids—were grouped under Anthropoidea (/an'thro-poy'de-a/, Gr. άνθρωπος, anthropos, human), while the strepsirrhines and tarsiers were grouped under the suborder "Prosimii". Under modern classification, the tarsiers and simians are grouped under the suborder Haplorhini while the strepsirrhines are placed in suborder Strepsirrhini. Despite this preferred taxonomic division, the terms "anthropoid" and "prosimian" are still regularly found in textbooks and the academic literature because of familiarity, a condition likened to the use of the metric system in the sciences and the use of customary units elsewhere in the United States.

Primatology, paleoanthropology, and other related fields are split on their usage of the synonymous infraorder names, Simiiformes and Anthropoidea. According to Robert Hoffstetter, and supported by Colin Groves, the term Simiiformes has priority over Anthropoidea because of the taxonomic term Simii by van der Hoeven, from which it is constructed, dates to 1833. In contrast, Anthropoidea by Mivart dates to 1864, while Simiiformes by Haeckel dates to 1866, leading to counterclaims of priority. Hoffstetter also argued that Simiiformes is also constructed like a proper infraorder name (ending in -iformes), whereas Anthropoidea ends in -oidea, which is reserved for superfamilies. He also noted that Anthropoidea is too easily confused with "anthropoïdes", which translates to "apes" from several languages.

The simians are split into three groups. The New World monkeys in parvorder Platyrrhini split from the rest of the simian line about 40 mya, leaving the parvorder Catarrhini occupying the Old World. This group split about 25 mya between the Old World monkeys and the apes. "Monkeys" are a paraphyletic group (i.e. not a single coherent group).

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

• ORDER PRIMATES
  • Suborder Strepsirrhini: non-tarsier prosimians
  • Suborder Haplorhini: tarsiers, monkeys and apes
    • Infraorder Tarsiiformes
    • Infraorder Simiiformes
      • Parvorder Platyrrhini: New World monkeys
        • Family Callitrichidae: marmosets and tamarins
        • Family Cebidae: 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, including humans