10 Classification and Distribution of Living Primates

Mr. Vijit Deepani and Prof. A.K. Kapoor

epgp books

 

Contents:

  • Primates: A brief Outline
  • Classification of Living Primates
  • Distribution of Living Primates
  • Summary

 

Learning Objectives:

  • To understand the classification of living primates.
  • To discern the distribution of living primates.

 

Primates: A brief Outline

 

Primates reside at the initial stage in the series of evolution of man and therefore constitute the first footstep of man’s origin. Primates are primarily mammals possessing several basic mammalian features such as presence of mammary glands, dense body hair; heterodonty, increased brain size, endothermy, a relatively long gestation period followed by live birth, considerable capacity for learning and behavioural flexibility.

 

St. George J Mivart (1873) defined Primates (as an order) as “unguiculate, claviculate, placental mammals, with orbits encircled by bone; three kinds of teeth, at least at one time of life; brains always with a posterior lobe and calcarine fissure; the innermost digits of at least one pair of extremities opposable, hallux with a flat nail or none; a well-developed caecum; pendulous penis; testes with scrotum; two pectoral mammae.”

 

Thus following characteristics differentiate primates, as a group, from other mammals: (Swindler, 2004; Jurmain et al., 2012)

  • Prehensile limbs, Pentadactyly and Flattened Nails
  • Either thumb or great toe is opposable or both are opposable
  • Presence of well developed clavicle
  • Fingers and toe possess sensitive tactile pads (enriched with sensory nerve fibers) at the ends of digits
  • Generalized dentition
  • Orbits surrounded by bony rims, enhancement in visual depth perception, binocular vision
  • Increase in size and complexity of the brain
  • Primates possess two pectoral mammae, efficient means of fetal nourishment, longer gestation times.
  • Primates possess pendulous penis
  • Diurnal activity pattern (except some prosimians, new world monkey)
  • Tendency to reside in social groups

 

Classification of Living Primates

 

The term classification is often used interchangeably with terms ‘systematics’ and ‘taxonomy’. Simpson (1961) defined Systematics as the scientific study of the kinds and diversity of organisms and of any and all relationships among them. Systematics provides insight into the evolutionary relationships between organisms and taxonomy deals with classification and nomenclature of organisms. The key (groups different organisms together if they share one striking character), the Phenetic (or natural – groups organisms in accordance to their degree of overall resemblance often in morphology or other observable features, regardless of their phylogeny or evolutionary relation) and the Phyletic (or phylogenetic – attempts to group organisms in accordance to their evolutionary relationships) – constitute three major types of classification.

 

Swedish naturalist Carl Linnaeus had made pivotal contribution to the present hierarchial classification of animals. Kingdom, phylum or division, class, order, family, genus, species- are seven major taxonomic ranks and species (or biological species) is designated as the basic unit of classification.

 

Thus classification of primates simply implies ordering of primates into groups on the basis of their relationship to each other though descent from a common ancestor. The prime motive of any classification is therefore to develop a hierarchical system of categories of increasing rank.

 

The term ‘Primates’ was first used by Carolus Linnaeus to encompass four genera: Homo (man), Simia (all monkeys and apes of the Old world and New world then known), Lemur and Verspetilio (bats) and later bats were removed from the order (Swindler, 2004). In 1971, J. F. Blumenbach proposed a primate classification where he categorized primates into two orders, Binama (included man) and Quadrumana (included apes, monkeys and lemurs) (Shukla and Rastogi, 2011). The classification was not accepted worldwide.

Fig I: Taxonomic classification of animals

(Source: Lewis et al., 2007).

Figure I depicts classification scheme of animals and thus the taxonomic specification of order Primate can be represented as:

Category Taxon
Kingdom Animalia
Subkingdom Metazoa
Phylum Chordata
Subphylum Vertebrata
Class Mammalia
Order Primates

 

G.G.   Simpson in 1945 proposed a primate classification, whereby the morphological resemblance among the primate species was utilized as basic and sole criteria of classification. His classification proposal was comparatively simple. He differentiated man (Hominidae) from apes (Pongidae) at family level and classified australopithecines (hominins) with pongids and if the morphological resemblance exhibits evolutionary relationship, then the traditional classification emphasized that hominid branch was first to separate from pongids which later differentiated into all extant ape genera and species (Ayala and Cela-conde,2017).

 

Figure II (below) exhibits the classification of living primates. The order primate order is a part of a larger group, the class Mammalia (phylum Chordata). The former is categorized into two traditional suborders, namely, categories, Prosimii (all the prosimians: lemurs, lorises, and, customarily, the tarsiers) and Anthropoidea (all the monkeys, apes, and humans). An important point to be emphasized here is that the suborder distinction is more specific than the order (Jurmain et al., 2012). At the suborder level, the prosimians form a separate group which is different from all the other primates. The above statement is biological and evolutionary relevant. Similarly, all anthropoid species are more closely linked to each another than they are to the prosimians.

 

An alternative classification scheme was also supported by certain section of Primatologists in which tarsiers and anthropoids were grouped in the suborder Haplorhini and lemurs, lorises and galagos were placed in suborder Strepsirhini (Ayala and Cela-conde, 2017). The anatomy of the nose was the base of this classification as the nose of strepsirhine primates is composed of a moist rhinarium and a lateral slit or crease (‘strepsis’ meaning twisting) and the nose of haplorhine primates lacked moist rhinarium (‘haplos’ meaning simple and unadorned condition).

Fig II: Difference in the structure of strepsirhine and haplorhine primate nose

(Source: Swindler, 2004).

 

Traditionally, taxonomic classification relied upon physical similarities between species and lineages but with the advent of genetic technologies (such as the DNA-sequencing techniques), surplus genetic evidence have emerged over the past few years that provide direct between-species comparisons of DNA sequences (Jurmain et al., 2012). Goodman and his colleagues emphasized that humans and chimpanzees have only a 1.6% difference in the non-coding portions of their globin gene clusters, whereas there is a 2.1 percent difference between chimpanzees and gorillas (Gibbons, 1990) and when the entire genome is considered, reported differences between chimpanzees and humans range from 2.7 percent (Cheng et al., 2005) to 6.4 percent (Demuth et al., 2006). Genetic similarities in relation with fossil evidence highlighted that humans and chimpanzees last shared a common ancestor around 6–8 mya.

 

Prosimians (Halbaffen or before-apes) are referred to as the lower primates owing to their primitive morphology and behaviour. The suborder Prosimii included three infraorder namely, Lemuriformes (all lemurs), Lorisiformes (all Lorises and Galagos) and Tarsiformes (all Tarsiers). On the other hand, anthropoids (monkeys, apes and man) – ‘manlike’ primates- are termed the higher primates. The suborder Anthropoidea comprised of two infra-orders Platyrrhini (all New World Monkeys) and Catarrhini (all Old World Monkeys, apes and humans).

 

Several traits differentiate anthropoids, as a group, from prosimians (and most other placental mammals). Jurmain et al. (2012) provided account of these traits:

 

1.  Generally larger body size

 

2.  Larger brain (in absolute terms and relative to body weight)

 

3.  Reduced dependence on the sense of smell, as indicated by absence of a rhinarium

 

4.  Increased reliance on vision, with forward-facing eyes at the front of the face

 

5.  Greater degree of color vision

 

6.  Back of eye socket formed by a bony plate

 

7.  Blood supply to brain different from that of prosimians

 

8.  Fusion of the two sides of the mandible at the midline to form one bone (in prosimians they are two bones joined by fibrous tissue)

 

9.  Less specialized dentition, as seen in the lack of a dental comb and some other features

 

10.  Differences in female internal reproductive anatomy

 

11.  Longer gestation and maturation periods

 

12.  Increased parental care

 

13.  More mutual grooming

Fig III: Classification of Living Primates

(Source: Jurmain et al., 2012)

 

In present scenario, the living primates can be categorized into following six natural groups- (Martin, 1994)

 

i. Lemurs of Madagascar

 

ii. The Lorises and bush babies of Africa and Asia

 

iii. The Tarsiers of Southeast Asia

 

iv. The New World Monkeys of Central and South America

 

v. The Old World Monkeys of Africa and Asia and

 

vi.  The apes of Africa and Asia and Humans

Fig IV: Six groups of Living Primates

(Source: Martin, 1994)

 

Living Primates: Distribution

 

Zoogeography is scientific study of distribution of living animals. Today, majority of primate species inhabit tropical or semitropical regimes of the New and Old Worlds (with certain exceptions). In New World, these regions comprise of Southern Mexico, parts of South America and Central America and in Old World, these areas include Africa, Southeast Asia (including numerous islands), India and certain areas of China and Japan.

 

Fig V: Geographical distribution of extant nonhuman primates

(Source: Martin, 2012)

 

Fig VI: Primate Hands: the Family tree (Source Link: https://s-media-cache-

ak0.pinimg.com/originals/63/37/9a/63379aa03e55ba77bf82759f356a9a92.jpg)

Most of the primate species are mostly arboreal and inhabit forest or woodland ecological settings (Jurmain et al., 2012). Certain primate species (such as baboons) have adapted to life on the ground in places where trees are sparsely distributed. The African apes, namely, gorillas, chimpanzees, and bonobos also invest much time on the ground in forested and wooded ecological settings. But no nonhuman primate is adapted to a complete terrestrial lifestyle and thus they spend some time in the trees.

 

Lemurs and lorises

 

Lemurs and lorises constitute most primitive primates as they have retained several ancestral traits, such as a more pronounced dependence on the sense of smell (greater olfactory capabilities). Besides Lemurs and lorises also exhibit a distinctive character termed as “dental comb”.

 

Lemurs are specifically found in the island of Madagascar. They also inhabit nearby islands off the east coast of Africa. Lemurs have successfully adapted to occupy numerous open ecological niches in absence of competition from monkeys and apes as they made their way to Madagascar. Lorises primarily inhabit tropical forest and woodland habitats of Africa, Southeast Asia, India and Sri Lanka. Nycticebus or slow loris resides in jungles of Southeast Asia and some of the western islands of the Indonesian archipelago

 

Tarsiers

 

They are small nocturnal primates and supreme leapers. They relate to one genus, Tarsius, which includes five tarsier species and the species are restricted to island regime in Southeast Asia and the Philippine Islands. These primates reside in a wide array of habitats ranging from tropical forest to backyard gardens and prefer small vertebrates and insects as their prey. Tarsiers are nocturnal insectivores that leap from lower branches and shrubs onto prey (which may include small vertebrates) and the basic tarsier social unit is a mated pair and their young offspring. They are characterized by enormous eyes, which dominate much of their facial region.

 

New World Monkeys

 

The New World monkeys or platyrrhines (included in the superfamily Ceboidea.) constitute tropical arboreal primates residing in the forest areas of Central and South America and Mexico. They are dichotomized into two families: Callitrichidae (marmosets and tamarins) and Cebidae (all other New World Monkeys). New World monkeys are diurnal with only one exception (Aotus), and some never come to the ground. Like Old World monkeys, all except one species (the owl monkey) are diurnal.

 

Marmosets and Tamarins (Callitrichids)

 

They are the smallest of the New World monkeys. They are arboreal quadrupeds having claws on all their digits. Their diet consists largely of insects, although marmosets eat gums from trees, and tamarins eat fruits. Socially, these small monkeys live in family groups usually composed of a mated pair, or a female and two adult males, and their offspring. Unlike other primates, marmosets and tamarins usually give birth to twins, and they’re among the few primate species in which males are extensively involved in infant care.

 

Cebids

 

The family Cebidae is comprised of eleven primate genera which further encompass a wide range of animals. Cebids are larger in size in comparison to Callitrichids. Cebids are only primates characterized with prehensile tail. Most cebid exhibit quadrupedal locomotion; but some (such as muriquis and spider monkeys) are semi-brachiators. The members of Cebidae reside in communities (exception: night monkeys).

 

Old world Monkeys

 

Old world Monkeys are placed under superfamily Cercopithecoidea and one taxonomic family Cercopithecidae and this family is further subdivided into two subfamilies namely, the Cercopithecinae (non-leaf eating) and Colobinae (leaf eating). Cercopithecines are different from the colobines because former lack sacculated stomach and possess cheek pouches (for temporary food storage).

 

Leaf eating monkeys such as Colobus monkey, Proboscis monkey, Snub-nosed monkey, Hanuman Langurs reside in Africa (only one genus Colobus), India, Indonesia, Malaysia, Java, Sumatra, Borneo and China. Old World monkeys represent the most widely distributed living primates except Humans because they inhabit a wide array of ecological domains ranging from tropical jungle habitats to semiarid desert throughout sub-Saharan Africa and southern Asia and even to seasonally snow-covered regions in northern Japan.

 

Non-leaf eating primate species such as Macaques and Baboons have also colonized wide environmental settings such as rain forests, arid scrublands, grasslands and mountainous slopes. They are found throughout Africa and Asia. They have omnivorous diet and eat about anything which is edible in their environmental setting. Today, the genus Macaca exhibit widest geographical distribution among all Old world Monkeys ranging from Morocco in North-western Africa to the Northern end of Honshu Island in Japan.

 

Most of Old World monkeys are quadrupedal and primarily arboreal, but certain species such as baboons, macaques, and langurs exhibit terrestrial lifestyle and spend much of the day on the ground. Sexual dimorphism is a typical trait among some terrestrial species and particularly pronounced in baboons.

 

Females of certain species, especially baboons and some macaques, exhibit marked cyclical changes of the external genitalia.

 

 

Apes and humans

 

The anthropoid apes and Humans are grouped under superfamily Hominoidea. The superfamily Hominoidea encompasses three families, namely, Hylobatidae, Pongidae and Hominidae. Apes and humans are differentiated from monkeys on the basis of following attributes: (Jurmain et al., 2012)

 

1.  Generally larger body size, except for gibbons and siamangs

 

2.  Absence of a tail

 

3.  Shorter and more stable lower back

 

4.  Arms longer than legs (apes only)

 

5.    Differences in position and musculature of the shoulder joint, which is adapted for suspensory behaviors (brachiation and/or feeding)

 

6.  Generally more complex behavior

 

7.  More complex brain and enhanced cognitive abilities

 

8.  Increased period of infant development and dependency

 

 

Apes

 

The anthropoid apes can be dichotomized into two broad groups:

 

(a) Gibbon – the lesser apes – family Hylobatidae

 

(b) Chimpanzee, Gorilla and Orangutan – the Great apes – family Pongidae

 

The gibbons and siamangs belong to gibbon family. The gibbons (comprised of several species) are found to inhabit various parts in Southeast Asia, including Northeast India and Burma and also in many of the islands of the Indo-Malayan archipelago. The Siamangs are found in the island of Sumatra. Gibbons are true brachiators and the acrobats of the primates (Swindler, 2004).

 

The orangutans (encompass two species- Pongo pygmaeus pygmaeus and P. pygmaeus abelli)-only great ape from Asia – are confined to Islands of Borneo and Sumatra. This frugivorous pongid resides in dense rain forests and follows arboreal lifestyle and rarely come to ground. They do not brachiate and spend much of their time in trees suspended by their long arms as they slowly progress through the dense forests (Swindler, 2004).

 

The Gorillas are considered the largest and stoutest among all living primates owing to their body dimensions. There are three geographical variants of gorilla- a Western lowland gorilla, Eastern lowland and a Mountain gorilla (Rosen, 1974). They are regarded as single species with three subspecies. Gorillas (Gorilla gorilla) inhabit forested areas of western and eastern equatorial Africa and the mountain gorilla specifically inhabit the Virunga range of extinct volcanic mountains of Uganda and Rwanda. They are knuckle walkers and spend most of their time on the ground and follow a vegetarian diet.

 

Chimpanzees and Bonobos

 

The Chimpanzee (Pan troglodytes) and Bonobos (Pan paniscus) ( sometimes called “pygmy chimpanzees”) are the remaining great apes. The former are found in equatorial Africa, in an area that stretches from the Atlantic Ocean in the west to Lake Tanganyika in the east and the latter are confined in an area south of the Zaire River in the Democratic Republic of the Congo (DRC) (Jurmain et al., 2012). Chimpanzees follow arboreal lifestyle and are capable of standing and walking erect. They prefer to eat large amount of fruits, seeds and vegetables but occasionally they prefer to hunt in groups and kill small mammals such as red colobus monkeys, young baboons, bush pigs, and antelope.

 

Humans

 

The family Hominidae is represented by Homo sapiens – the only extant member of the genus Homo. Homo sapiens are the most widely dispersed primate species because they have successfully inhabited diverse ecological domains. They represent one of the final products of an evolutionary radiation which also led to the evolution of other species in the same genus such as Homo neanderthalensis (which have now become extinct).

 

Summary

 

The present attempt throws light upon taxonomic specifications and geographical distribution of living primates. Taxonomic classification helps scientists to organize living organism in a hierarchial system of categories of increasing rank on the basis of biological and evolutionary relationships among living creatures. It provides better understanding and communication of extant and extinct living creatures.

 

 

In the present context, classification of primates basically refers to hierarchial ordering of primates into groups on the basis of their relationship to each other though descent from a common ancestor. Primates constitute a diverse and vast group of mammals represented by humans, monkeys, prosimians and apes. All the primate species share several common characteristics at order level but as we move towards more specific classification levels (such as superfamily, family and genus) a great deal of variation is exhibited and all criteria of relationships are centered upon essential identities of structure and development. Primate classification is in transitional state owing to surplus genetic evidence that has emerged over the past few years with advancement in genetic technologies (such as DNA sequencing techniques).

 

Primates reside in complex environmental settings characterized by constantly changing attributes. Today nonhuman primates exist in five of the seven continents as there are no living primates in Antarctica and Australia (exception being humans). Most of the nonhuman primate species follow arboreal lifestyle and reside in Africa, Asia and South America, and their nearby islands. Primate species have successfully inhabited a wide array of habitats ranging from dry and arid deserts to tropical forests. Most of the primate species reside in tropical forests of different kinds and may also occupy different niches even within a particular forest.

 

Certain primate species such as baboons and patas monkeys follow partially terrestrial lifestyle and few species such as geladas and humans are fully terrestrial. Also certain primate species such as mountain gorilla and black snub-nosed monkey have also inhabited high altitude settings.

you can view video on Classification and Distribution of Living Primates

 

References:

  • Ayala, F. J. and Cela-Conde, C. J. (2017). Processes in Human Evolution: The Journey from Early Hominins to Neandertals and Modern Humans. Oxford University Press.
  • Cheng, Z., Ventura, M., She, X., Khaitovich, P., Graves, T., Osoegawa, K., Church, D. et al. (2005). A genome-wide comparison of recent chimpanzee and human segmental duplications. Nature, 437(7055), 88-93.
  • Demuth, J. P., De Bie, T., Stajich, J. E., Cristianini, N., & Hahn, M. W. (2006). The evolution of mammalian gene families. PloS one, 1(1), e85.
  • Gibbons, A. (1990). Our chimp cousins get that much closer. Science 250: 376.
  • Jurmain, R., Kilgore, L. & Trevathan, W. (2012). Essentials of Physical Anthropology (8thed) .Wadsworth, Belmont, CA.
  • Jurmain, R., Kilgore, L., & Trevathan, W. (2007). Essentials of Physical Anthropology.
  • Lewis, R. Barry & Jurmain, Robert & Kilgore, Lynn (2007). Understanding physical anthropology and archaeology (9th ed). Thomson Wadsworth, Belmont, CA
  • Martin, R.D. (1994). Classification of primates. In the Cambridge Encylopaedia of Human Evolution.
  • Ed. S. Jones, R. D. Martin, and D. Pilbeam. Cambridge University Press, Cambridge.
  • Martin, R.D. (2012). Primates. Current Biology. 22(18); R785 – R790.
  • Mivart, St. George. (1873). On Lipilemur and Cheirogaleus and on the zoological rank of the Lemuroidea. Proceedings of the Zoological Society of London, 484-510.
  • Rosen, S. I. (1974). Introduction to the Primates: Living and Fossil. Prentice – Hall Inc., Engelwood Cliffs, New Jersey.
  • Shukla, B. R. and Ratogi, S. (2011). Physical Anthropology and Human Genetics – An Introduction.Palaka Prakashan.
  • Simpson, G. G. (1961). Principles of animal taxonomy. Columbia University Press.
  • Swindler, D. R. (2004). Introduction to the Primates. University of Washington Press.