What are Primates?

Introduction

In the taxonomic classification of the animal kingdom, class mammalian of phylum vertebrate comprises animals possessing evolutionarily advanced traits. The class Mammalia has been further categorized into 19 subtaxa called orders. Among those, order primate includes a diversified group of animals such as Lemurs, Lorises, Tarsiers, Monkeys, Apes and Humans.

Table of Content:

Evolution of Class Primata:

  • Based on the paleontological evidence found in North America and Europe, the primates may have evolved 55 – 60 million years ago in these continents.
  • The oldest primate-like mammals or proto primate is known to be plesiadapis. They were found in Europe and North America in the Cenozoic era and believed to have gone extinct by the end of Eocene epoch.
  • The fossils of primates were found in North America, Asia and Africa, which belongs to Eocene epoch. They resembled present-day lemurs. It has been believed that monkeys arose in the old world (Europe, Asia and Africa) and reached the New world (America) by drifting on logs or with floating islands.
  • Due to this, new world monkeys and old world monkeys were reproductively isolated and followed different adaptive radiations over 30 million years
  • Evolution of prosimians occurred during Oligocene epoch. All living species of present-day primates got evolved some 30 million years ago.
  • Recent estimates reveal that there are 230 to 270 primate species that exist today.

General Characteristics of primates

  • Since all primates are descendent of tree-dwellers, they exhibit adaptive features which allow them to climb trees. These include:
  • A rotating shoulder joint: This is due to secure ball joints and strong clavicles or collarbones, which have allowed them to use their arms very effectively in climbing trees.
  • Separated big toes and thumb for grasping: This is because all primates, except spider monkeys, have pentadactylism (having five fingers and toes on hands and feet respectively). The mobility of fingers and toes with opposability of thumb makes grasping easier. All primates, other than humans, also have prehensile feet. Partially rotating the thumb and pressing it forcefully towards the fingers provides power grip for small world monkeys. The monkey and apes are more dexterous and can grip with precision. This allows them to manipulate small objects effectively.
  • Stereoscopic vision: Primates have increased visual capabilities than other mammals. Fifty percent of cerebral cortex in primates is involved in visual processing function. Colour vision along with binocular vision results in stereoscopic vision.

Other characteristics of Primates

  • Most primates are arboreal, or tree-living (Notable exceptions are humans and gorillas).
  • Most primates show erectness in the upper body and exhibit occasional bipedalism (Humans are erect and always exhibit bipedalism).
  • All primates have reduced nose size with corresponding olfactory areas of the brain (except Lemurs).
  • Primate brains are large relative to their body size, compared to other mammals. The expanded areas of the brain are responsible for controlling manual dexterity, hand-eye coordination, and stereoscopic vision.
  • Long gestational periods with respect to animal size.
  • In general, primates are highly social animals.
  • Almost all primates are diurnal.
  • The advanced primates, including humans, have a very pleasurable activity called Grooming.

Classification of Primates

Classification of Primates

Classification of primates is primarily based on the similarities and dissimilarities of external morphology, although phylogenetic classifications have also been done. Primates consist of two suborders: Strepsirrhini and Haplorrhini.

Strepsirrhini:

  • They have moist, large hairless nose tip.
  • They were the first of the suborders of primate to evolve.
  • They are also called “lower Primates” and also referred to as “Prosimians”
  • Prosimians means “Pre-Monkey”.
  • Lemurs, Lorises and related animals are included in this group.
  • They are inhabited in most tropical regions of the earth.
    • Lemurs:
  • They are found exclusively in Madagascar islands and the nearby Comoro Islands.
  • There are almost 22 arboreal species of lemurs living today.
  • There are five surviving families of lemur.
  • Lorises:
    • They are mainly seen in India and south-east Asia.
    • They are arboreal and omnivores, even though they feed on easy prey like insects, eggs and baby birds.
    • They are nocturnal (night loving).
  • Tarsiers:
    • Tarsiers of Southeast Asia are large rat size.
    • They possess both prosimian and monkey-like traits. Yet, they differ significantly from both the groups in genetic makeup.
    • Their natural habitat is southern Philippines, Borneo and the Celebes islands.
    • There are at least seven surviving species of tarsiers who mostly depend on vision and hearing with reduced ability to smell.
    • Able to produce ultrasounds for their internal communications.
    • Able to rotate their heads more than 180°.
    • Strictly Nocturnal and carnivores.

Haplorrhini:

  • Possess flat nose.
  • Considered to be “higher primates” and also called as “Anthropoids”.
  • There are 145 living species under this suborder. Among those, over 90% are monkeys and remaining are apes and human.
  • Most successful primates in the earth.

On the basis of nose and number of a specific type of teeth, anthropoids are classified into; Platyrrhini (New World Monkeys) and Catarrhini (Old World monkeys, Apes and Human).

Platyrrhini (New World Monkeys)

  • Flat nose with nostrils projecting sideways separated by a wide septum.
  • Dental formula 2132 or 2133.
  • Seen only in tropical forest of southern Mexico, central and south America.
  • Exclusively arboreal and herbivore.
  • Many members have a tail as a third hand.
  • Includes 2 families: Cebidae and Callitricidae comprising 53 species
  • Cebidae includes squirrel and Capuchin monkey, night and titi monkeys, Howler and spider monkeys, Uakaris and sakis.
  • Callitricidae consist of Marmosets and tamarins.

Catarrhini (Old World monkeys, Apes and Human)

  • Downward projecting nostrils with small narrow septum separating them.
  • Inhabitants of south and east Asia, the Middle East and Africa.
  • Comprises 7 species in two families, namely Cercopithecinae and Colobinae.
  • Cercopithecines includes baboons, Mangabeys, Mandrills, guenons, patas monkeys and Macaques.
  • Macaques are most successful by spreading all over the world and mostly used for clinical research purposes.
  • Colobines are also called as leaf-eating monkeys.
  • They have sacculated stomach for better digestion of plant materials.

Apes and Humans:

  • Both are members of Superfamily Hominoidae and further divided into two families viz., Hylobatidae (Gibbons) and Hominidae (Orangutans, African apes {gorilla and chimpanzee} and Human).
  • Gibbons:
    • Also called lesser apes.
    • They are excellent brachiators (suspensory climbing) and are monogamous.
  • Orangutans:
    • Largest and rarest Asian apes.
    • Usually walks by quadrupedal.
    • Facing the danger of extinction.
  • African Apes:
    • Gorilla – Largest Apes.
    • Possessing “quadrupedal knuckle walkers”.
    • As of 2011, only 786 gorillas in the world.
    • Chimpanzees – More closely resemble humans than a gorilla.
    • Quadrupedal knuckle walkers as a gorilla
    • Intelligent animals with generally pleasant personalities.
    • Their interactions can be quite noisy, violent, and sometimes fatal.
  • Bonobos:
    • Close relatives of chimpanzees.
    • Sometimes referred to as pygmy chimpanzees.
  • Humans:
    • Only living species – Homo sapiens.
    • Shows sexual dimorphism similar to that of other apes.
    • Humans and African apes have the same internal organs, same bones and some blood group in common.
    • Erect posture and bipedalism due to modified pelvic bone sand spinal column.
    • Human and chimpanzee share 96% similarities in DNA base-pair sequences.
    • This shows that the two species had a common ancestor and got evolved into separated species 6-7 million years ago.

Questions and Answers:

  1. Write in brief about tarsiers.
    • Tarsiers of Southeast Asia are large rat size.
    • They possess both prosimian and monkey-like traits. Yet, they differ significantly from both the groups in genetic makeup.
    • Their natural habitat is southern Philippines, Borneo and the Celebes islands.
    • There are at least seven surviving species of tarsiers who mostly depend on vision and hearing with reduced ability to smell.
    • Able to produce ultrasounds for their internal communications.
    • Able to rotate their heads more than 180°.
    • Strictly Nocturnal and carnivores.
  2. Give a brief account of New World Monkeys.

New world monkeys have the following characteristics:

  • Flat nose with nostrils projecting sideways separated by a wide septum.
  • Dental formula 2132 or 2133.
  • Seen only in tropical forest of southern Mexico, central and south America.
  • Exclusively arboreal and herbivore.
  • Many members have a tail as a third hand.
  • Includes 2 families: Cebidae and Callitricidae comprising 53 species
  • Cebidae includes squirrel and Capuchin monkey, night and titi monkeys, Howler and spider monkeys, Uakaris and sakis.
  • Callitricidae consist of Marmosets and tamarins.

 

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