Monkey. Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as the simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes, which constitutes an incomplete paraphyletic grouping; however, in the broader sense based on cladistics, apes are also included, making the terms monkeys and simians synonyms in regard to their scope. In 1812, Geoffroy grouped the apes and the Cercopithecidae group of monkeys together and established the name Catarrhini, Old World monkeys. The extant sister of the Catarrhini in the monkey group is the Platyrrhini. Some nine million years before the divergence between the Cercopithecidae and the apes, the Platyrrhini emerged within monkeys by migration to South America likely by ocean. Apes are thus deep in the tree of extant and extinct monkeys, and any of the apes is distinctly closer related to the Cercopithecidae than the Platyrrhini are. Many monkey species are tree-dwelling, although there are species that live primarily on the ground, such as baboons. Most species are mainly active during the day. Monkeys are generally considered to be intelligent, especially the Old World monkeys. Within suborder Haplorhini, the simians are a sister group to the tarsiers-the two members diverged some 70 million years ago. New World monkeys and catarrhine monkeys emerged within the simians roughly 35 million years ago. Old World monkeys and apes emerged within the catarrhine monkeys about 25 million years ago. Extinct basal simians such as Aegyptopithecus or Parapithecus are also considered monkeys by primatologists. Lemurs, lorises, and galagos are not monkeys, but strepsirrhine primates. The simians' sister group, the tarsiers, are also haplorhine primates; however, they are also not monkeys. Apes emerged within monkeys as sister of the Cercopithecidae in the Catarrhini, so cladistically they are monkeys as well. However, there has been resistance to directly designate apes as monkeys, so Old World monkey may be taken to mean either the Cercopithecoidea or the Catarrhini. That apes are monkeys was already realized by Georges-Louis Leclerc, Comte de Buffon in the 18th century. Linnaeus placed this group in 1758 together with the tarsiers, in a single genus Simia, an ensemble now recognised as the Haplorhini. Monkeys, including apes, can be distinguished from other primates by having only two pectoral nipples, a pendulous penis, and a lack of sensory whiskers. The Barbary macaque is also known as the Barbary ape. According to the Online Etymology Dictionary, the word monkey may originate in a German version of the Reynard the Fox fable, published c. In this version of the fable, a character named Moneke is the son of Martin the Ape. In English, no clear distinction was originally made between ape and monkey; thus the 1911 Encyclopedia Britannica entry for ape notes that it is either a synonym for monkey or is used to mean a tailless humanlike primate. Colloquially, the terms monkey and ape are widely used interchangeably. Also, a few monkey species have the word ape in their common name, such as the Barbary ape. Later in the first half of the 20th century, the idea developed that there were trends in primate evolution and that the living members of the order could be arranged in a series, leading through monkeys and apes to humans. Monkeys thus constituted a grade on the path to humans and were distinguished from apes. Scientific classifications are now more often based on monophyletic groups, that is groups consisting of all the descendants of a common ancestor. The New World monkeys and the Old World monkeys are each monophyletic groups, but their combination was not, since it excluded hominoids. Thus, the term monkey no longer referred to a recognized scientific taxon. The smallest accepted taxon which contains all the monkeys is the infraorder Simiiformes, or simians.