Tarsier in the context of "Haplorhini"

Tarsiiformes /ˈtɑːrsi.ɪfɔːrmiːz/ are a group of primates that once ranged across Europe, northern Africa, Asia, and North America, but whose extant species are all found in the islands of Southeast Asia. Tarsiers (family Tarsiidae) are the only living members of the infraorder; other members of Tarsiidae include the extinct Tarsius eocaenus from the Eocene, and Tarsius thailandicus from the Miocene. Two extinct genera, Xanthorhysis and Afrotarsius, are considered to be close relatives of the living tarsiers, and are generally classified within Tarsiiformes, with the former grouped within family Tarsiidae, and the latter listed as incertae sedis (undefined). Omomyids are generally considered to be extinct relatives, or even ancestors, of the living tarsiers, and are often classified within Tarsiiformes.

Other fossil primates, including Microchoeridae, Carpolestidae, and Eosimiidae, have been included in this classification, although the fossil evidence is debated. Eosimiidae has also been classified under the infraorder Simiiformes (with monkeys and apes), and most experts now consider Eosimiidae to be stem simians. Likewise, Carpolestidae is often classified within the order Plesiadapiformes, a very close, extinct relative of primates.

A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of convergent evolution. The arrangement of the members of a polyphyletic group is called a polyphyly /ˈpɒlɪˌfaɪli/. It is contrasted with monophyly and paraphyly.

For example, the biological characteristic of warm-bloodedness evolved separately in the ancestors of mammals and the ancestors of birds; "warm-blooded animals" is therefore a polyphyletic grouping. Other examples of polyphyletic groups are algae, C4 photosynthetic plants, and edentates.

In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria:

1. the grouping contains its own most recent common ancestor (or more precisely an ancestral population), i.e. excludes non-descendants of that common ancestor
2. the grouping contains all the descendants of that common ancestor, without exception

Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A paraphyletic grouping meets 1. but not 2., thus consisting of the descendants of a common ancestor, excepting one or more monophyletic subgroups. A polyphyletic grouping meets neither criterion, and instead serves to characterize convergent relationships of biological features rather than genetic relationships – for example, night-active primates, fruit trees, or aquatic insects. As such, these characteristic features of a polyphyletic grouping are not inherited from a common ancestor, but evolved independently.

Nocturnality is a behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is nocturnal, with diurnal meaning the opposite.

Nocturnal creatures generally have highly developed senses of hearing, smell, and specially adapted eyesight. Some animals, such as ferrets, have eyes that can adapt to both low-level and bright day levels of illumination (see metaturnal). Others, such as bushbabies and (some) bats, can function only at night. Many nocturnal creatures including tarsiers and some owls have large eyes in comparison with their body size to compensate for the lower light levels at night. More specifically, they have been found to have a larger cornea relative to their eye size than diurnal creatures to increase their visual sensitivity: in the low-light conditions. Nocturnality helps wasps, such as Apoica flavissima, avoid hunting in intense sunlight.

The parvorder Catarrhini /kætəˈraɪnaɪ/ (known commonly as catarrhine monkeys, Old World anthropoids, or Old World monkeys) consists of the Cercopithecoidea (Old World monkeys) and Hominoidea (apes). In 1812, Geoffroy grouped those two groups together and established the name Catarrhini, "Old World monkeys", ("singes de l'Ancien Monde" in French). Its sister in the infraorder Simiiformes (simians) is the parvorder Platyrrhini (New World monkeys). There has been some resistance to directly designate apes (and thus humans) as monkeys despite the scientific evidence, so "Old World monkey" may be taken to mean 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 what we now recognise as the tarsiers and the New World monkeys, in a single genus "Simia" (sans Homo). The Catarrhini are all native to Africa and Asia. Members of this parvorder are called catarrhines.

The Catarrhini are the sister group to the New World monkeys, the Platyrrhini. Some six million years before the ape - Cercopithecoidea bifurcation, the Platyrrhini emerged within "monkeys" by migration to South America from Afro-Arabia (the Old World), likely by ocean.

Afrotarsius is a primate found in the Paleogene of Africa.

The first species to be named, Afrotarsius chatrathi, was named in 1985 on the basis of a single lower jaw from the Oligocene of Fayum, Egypt, and tentatively referred to the tarsier family (Tarsiidae). However, this relationship immediately proved controversial, and in 1987 the animal was placed in a separate family Afrotarsiidae related to simians. A tarsier-like tibiofibula was allocated to Afrotarsius in 1998, but the identity of this bone is controversial. In 2010, a second species of the genus, Afrotarsius libycus, was named from the Eocene of Dur At-Talah, Libya, on the basis of isolated upper and lower teeth. Features of these teeth were interpreted as additional evidence for a relationship between Afrotarsius and anthropoids. A second afrotarsiid genus, Afrasia, was named in 2012 from the Eocene Pondaung Formation of Myanmar. In the same paper, Afrotarsiidae was placed together with the Asian Eosimiidae in an infraorder Eosimiiformes, in the simians. However, some studies indicate that it should be placed in Tarsiiformes.