Scientists generally classify the order Primates into two suborders: Strepsirrhini (prosimians) and Haplorrhini (tarsiers and anthropoids). The Strepsirrhini or Prosimians The Strepsirrhini are considered to be primitive primates that evolved much earlier than other primates. This suborder includes lemurs and lorises. All the Strepsirrhini primates, or strepsirrhines, possess numerous anatomical traits that distinguish them from the Haplorrhini primates, or haplorrhines. These include a clawlike nail on the second toe, referred to as a grooming claw, and incisors in the lower jaw that are tightly packed together and protrude from the mouth, forming what is called a toothcomb. There are seven families of living strepsirrhines, and all of them are found in what anthropologists refer to as the Old World, which consists of the continents of Africa, Asia, and Europe. Five groups of living strepsirrhines are found only on the island of Madagascar off the coast of Africa. Two additional families are found in Africa and Asia. Figure 4.26 The pygmy slow loris (Nycticebus pygmaeus) is an example of a Strepsirrhini primate. Pygmy slow lorises be found in Vietnam, Laos, and a province of China. (credit: Lionel Mauritson/Wikimedia Commons, Public Domain) The Haplorrhini or Anthropoids The Haplorrhini are broken down into two further infraorders, Simiiformes and Tarsiiformes, and the Simiiformes are further divided into Platyrrhini and Catarrhini. The Platyrrhini, or platyrrhines, are exclusively found in the New World (specifically Central and South America) and are colloquially referred to as New World monkeys. Their name is derived from the rounded shape of their external nostrils, which open off to the sides. New World monkeys are also distinguishable by their prehensile tails that serves as an extra limb for extra support when moving in the trees. The Catarrhini, or catarrhines, are found throughout Africa and Asia. They differ from the New World primates in that they possess narrow nostrils that face downward. The Catarrhini contain two superfamilies, Cercopithecoidea and Hominoidea, and are exclusively Old World. The Cercopithecoidea contain two main groups: cheek pouch monkeys (Cercopithecinae) and leaf-eating monkeys (Colobinae). The most distinctive feature of the cercopithecoid primates is their molars, which exhibit two parallel ridges. The most distinguishing feature of the hominoids is that they do not have tails and are largely terrestrial, or ground-dwelling. Examples of Hominoidea include gibbons, chimpanzees, gorillas, orangutans, and humans. The Tarsier Puzzle The tarsier, which belongs to the family Tarsiidae, has both prosimian and anthropoid characteristics, which has made it difficult for scientists to classify. Tarsiers are currently classified within their own classification under the haplorrhines. One of the characteristics that tarsiers share with other haplorrhines, (including humans) is the inability to manufacture their own Vitamin C. They are the smallest known primate and are nocturnal, with extremely large eyes that take up much of the space in their skull. Due to their size of the eyes, the tarsier cannot rotate them; instead, it can rotate its head 360 degrees like an owl. Tarsiers are also the only primate carnivore, eating largely flying insects and sometimes small animals like bats and lizards. Tarsiers do not do well in captivity. They are extremely sensitive to noise and can become easily stressed. In fact, they can become so stressed that they die by suicide by banging their heads against tree trunks. Figure 4.27 The Philippine tarsier (Carlito syrichta) is found only in the southern portion of the Philippine islands. The tarsier has been challenging for scientists to classify, exhibiting both prosimian and anthropoid characteristics. (credit: “8thApril2007 – ‘Tarsier’ Monkey” by Jacky W./flickr, CC BY 2.0)