Introduction

Systematic and monumental description of life forms made human to make a detailed system of identification, nomenclature and classification of organisms i.e. Taxonomy

Taxonomy is the study of the principles and practice of classification, and is commonly used as a synonym for systematics, although the latter is, broader, covering all aspects of relationships among organisms.

Definition of a primate

the definition of a primate  is complex.

Unguiculate, claviculate, placental mammals, with orbits encircled by bone; three kinds of teeth, at least at one time of life; brain always with a posterior lobe and calcarine fissure; the innermost digit of at least one pair of extremities opposable; hallux with a flat nail or none; a well developed caecum; penis pendulous; testes scrotal; always two pectoral mammae. (Mivart 1873)

Unguiculate – possessing nails, hooves or claws

Claviculate – possessing a clavicle (collar bone)

Le Gros Clark described following characteristics-

1. Preservation of generalised limb structure with primitive pentadactyly. Describe primitive pentadactyly limb (3 girdle bones; 1 upper limb bone; 2 lower limb bones; carpals/tarsals; metas; phalanges), and how various other mammalian orders have lost various bones (especially fusing the lower limb bones).
2. Enhancement of free mobility of the digits, especially of the pollux and hallux (both used for grasping).
3. Replacement of sharp, compressed claws by flat nails; development of very sensitive tactile pads on the digits.
4. Progressive shortening of the snout.
5. Elaboration of the visual apparatus, with the development of varying degrees of binocular vision.
6. Reduction of the olfactory apparatus.
7. Loss of certain elements of the primitive mammalian dentition. Preservation of a simple molar cusp pattern. Tooth formula reduction: primitive mammal 3.1.4.3/3.1.4.3; prosimians and NWMs 2.1.3.3/2.1.3.3; OWMs & apes 2.1.2.3/2.1.2.3.  We have lost the anterior 2 premolars
8. Progressive expansion and elaboration of the brain, especially of the cerebral cortex.
9. Progressive and increasingly efficient development of gestational processes.
10. Prolongation of postnatal life periods.
11. Progressive development of truncal uprightness leading to a facultative bipedalism.

There is no unique characteristic that defines a primates. It is a list of shared characteristics and trends – most of which aren’t even derived, but are retentions of ancestral features, which is definitely not good. Many of these features are behavioural, or depend on soft tissue anatomy.

Prosimians and Simians

First primate like animals appeared in the Palaeocene (70 mya), perhaps even late Cretaceous. These are described as early prosimians.

Features

1. Tooth comb from incisors
2. Locomotor specializations: vertical clinging and leaping, slow quadrupedalism
3. Wet noses
4. Dog-like faces
5. Nocturnal
6. Orbital bar
7. Ectotympanic ring
8. Epitheliochorial placenta
9. Tapetum

Prosimians becoming strepsirhini and anthropoids becoming haplorhini. By this definition, tarsiers become haplorhines,. Many of these branches have the word “rhine” in them. This is from the Greek rhis, rhinos meaning nose, and generally refers to specific nasal anatomy that can be used to distinguish these groups. Strepsirhines have dog-like, wet noses, whereas the rest of the primates have dry noses.) First haplorhines (single noses), appeared in the Eocene. This group may be ancestral to the rest of the anthropoids.

Tarsiiformes

Features

1. VCL
2. Ectotympanic tube
3. Orbital closure
4. Extremely large eyes
5. Haemochorial placenta

The infraorders of platyrrhines (flat noses) and catarrhine (down facing noses) coincides neatly with the animals found in South America (the “New World”) and with those found in Africa and Asia (the “Old World”), so the terms are almost synonymous. New World Monkeys are all platyrrhines, but catarrhines include apes as well as OWMs.

About 40 mya (end of Miocene), monkeys have developed independently in quite a distinct pattern. New World monkeys are every bit as advanced as Old World monkeys with some very impressive adaptations that the OWMs lack such as prehensile tails. There are no prosimians in the New World. Their nocturnal insectivorous niche is taken up by other mammals such as opossums (South American marsupials), though there is also one nocturnal NWM, Aotus, the owl monkey .

New World Monkeys

Features

1. Poorly developed thumb & finger grip
2. Larger, more convoluted brain
3. Diurnal
4. Well developed tail – prehensile in some groups
5. Outward facing nostrils

Catarrhines

This group includes the rest of the monkeys and apes including humans and divided into 2 major groups:

1. hominoidea (apes) and
2. cercopithecoidea (monkeys).

Features

1. Better thumb & finger grip
2. Shorter (or no) tail
3. 2 premolars
4. down facing nostrils

Cercopithecoidea

1. Cercopithecines- Mixed diets. Macaques (note Barbary macaque), Baboons, Guenons.
2. Colobines-Leaf eaters. Colobus (Africa) and Langurs (Asia).

Hominoids

Late Oligocene (25 mya). Two extant families: hominidae and hylobatidae. Sone taxonomist have 3 families, with only humans as hominids, and a separate family, pongidae, for great apes.

Gibbons (hylobatids) are unique in habitually travelling by brachiation – swinging through the trees suspended by their arms. They are found in South East Asia

Features

1. Larger brains
2. No tails
3. Arms and shoulder girdle for suspension
4. Y-5 shaped pattern on molar teeth

Hominids

Early hominids/pongids appeared in the Miocene (20 mya). It includes Great apes (& humans). Orang-Utans of Borneo and Sumatra; Gorillas of central Africa; Chimpanzees – central Africa but more widespread; and Humans – almost everywhere.

Features

1. Still larger brains
2. Larger
3. Mostly terrestrial

Hominins

The real human group.