5 Significant Characteristics of Living Primates – Explained!


December 20, 2018 admin 0 Comment

He however does not consider this group as a member of the primate order. Straus has shown some fundamental differences between the tree-shrews and the lemurs in respect of some characters. He suggests a separate suborder, the Tupaioidea, for the tree-shrews, within the order primate. Straus suggestion has not yet been accepted by all. Therefore, here the tree-shrews have been dealt separately.

(i) Distribution:

Tupaioidea comprises the single living family Topside, which includes tow subfamilies. These again include six genera, about 32 species and some 100 subspecies. They are distributed in India, Burma, China, Borneo, and Sumatra. Philippine islands, Malaysia, etc.

(ii) Characters:

(a) External:

The tree-shrews are small animals, being squirrel-like in appearance. They are arboreal in their habits some of them are diurnal, while others are nocturnal animals. They are mainly insectivorous, but they eat anything that is digestible.

(b) Internal:

1. Their typical dental formula is I 2/3, C 1/1, PM 3/3, M 3/3.

2. Their digits are provided with sharp curved claws.

3. The manus and peps are adapted for grasping

4. Both pollex and halloo are opposable to some extent.

5. The tail is not prehensile. It is used as a balancing organ.

6. The skull resembles that of the lemur in many characters.

7. As in insectivores proper, in tree-shrews also the orbits are directed more laterally than that of the lemurs.

8. The rhinarium is naked, glandular and moist.

2. The Lemuridae:

(i) Distribution:

The Lemur idea comprises two families, namely, Lemuroid and Lopsided and several genera. Some of their living representatives are Indri, Lemur, and Loris. Gal ago etc. The present day lemurs are confined to the Old World. They are found in the tropical forests of Africa and in the island of Madagascar. Some members inhabit the Indonesian islands and the Philippines.

(ii) Characters:

(a) External:

1. The lemurs are small animals, the size varying from that of a mouse to that of a large cat.

2. They live on insects, fruits, leaves, shoots, nuts, eggs, etc.

3. They are arboreal and are mostly nocturnal in their habits.

4. The lemurs are coated with furry coverings.

5. They have long bushy tails which are not prehensile but help in balancing.

6. The hind limbs are usually somewhat longer than the forelimbs.

7. The thumb and great toes are opposable. ,

8. The hands and feet are adapted for grasping.

9. All digits of the hands and feet except the second digits of the hind limb, which bear claws, are provided with flat nails.

10. The lemurs have the naked rhinarium and crescent nostrils.

(b) Internal (b-I) Skull:

1. The postorbital wall is absent.

2. The eyes are directed outwards.

3. The lachrymal foramen or the tear duct is outside the orbit.

4. In the inner wall of the orbit portion of the palatine bone is present.

5. The skull is not balanced upon the vertebral column, but is suspended from occult condoles.

6. The external auditory meats are absent.

7. A large, spherical auditory bulla is present.

8. The jaw is elongated to give it fox-like appearance.

(B-2) Jaw

1. The typical detail formula is I/2: C1/, PM2/2: M3/3.

2. In the lower jaw the canines are inquisitor while the anterior premolars look like canine form

3. The canines and the incisors are placed in front of the jaw in a row like the teeth of his comb. These are separated from the first premolar by a gap.

3. Tarsioidea:

(i) Distribution:

The subfamily Tarsi idea comprises only one living family which has but a single genus Tarsus represented by a single species ‘Tarsus spectrum’. They are confined to the Malayan islands, e.g., Sumatra, Java, Borneo, Celebes, Philippines etc.

(ii) Chrematistics:

(a) External:

1. The tarsiers are small animals attaining to the size of a rat (adult body size about 8?).

2. They are usually insectivorous and are completely arboreal and nocturnal in their activities.

3. The tarsier can rotate its head for 180 so as to look backward without moving the body.

4. Another important feature is its salutatory or frog-like leaping movement.

5. The tarsiers have furry coverings, but some parts of the body are sparsely clothed with hair.

6. The hind-limbs are considerably, longer than the fore-limbs.

7. The tail is longer and tufted at the tip.

4. Ceboidea:

(a) Callithricidae:

This family is represented by the small, squirrel-sized Marmot sets. Their food mainly consists of fruits and insects. They are arboreal and diurnal in their habits.

They are clothed with soft and silky fur. All the digits, except the great toe, which bears flat nails, are provided with claws. The thumb is not opposable; the great toe, however, is capable of some amount of mobility. The length of the hind limbs exceeds that of the forelimbs. They possess non- prehensile tail which is usually tufted at its end. The nostrils are oval and widely separated.

The muzzle is absent. The auditory bulla is a large inflated chamber. The tympanic annulus is outside the cavity of the bulla. The dental formula is 12/2: C11/1: PM2/2: M3/3.

(b) Cebidae:

The Carbide comprises a large number of genera and species, which show diversified characters.

Some of the characters by which the Carbide may be distinguished from the Hepialid are: They are comparatively larger in size than the Marmosets. Most of them do not possess bushy tails. Their digits, except the first one, do not bear claws, but nails. The dental formula is 12/2: Cl/1: PM3/3: M3/3.

The members are: Rebus monkey, Spider monkey, Squirrel monkey, etc. Thus, the dental characters alone are sufficient to eliminate the consideration of placing man under Cambodia. Cercopithecoidea includes Cercopithecoidae, Hylobatidae and Hominidae.

5. Cercopithecidae (Old World Monkey):

The Old World Monkeys are arboreal in their habits. They are herbivorous and frugivorous. On the baboons are terrestrial and to some extent insectivorous. Among the members of this stoutly tail is of variable length, it may be very short or very long, but never prehensile.

The handler always exceeds the forelimb in length. All the digits are provided with flat nails. The eschewal callosities (sitting pad of naked modified skin at the buttocks) are always present.

The Old World Monkeys comprise two groups, namely, the cercopithecinae and the seniti pithecinae. The cercopithecinae includes the Celebes or black ‘apes’ macaques, guenons, baboon etc. The Celebes ‘apes’ are confined to Asia, China, Japan, Philippines, East Indies, North Aria and Gibraltar.

The baboons inhabit the regions of South Africa, Arabia and Abyssinia and the guenons are met with in different parts of Africa.

The members of this sub-family always have cheek pouches. All the digits including the thumb are well developed and provided with nails.

The Semnopithecinae is represented by lingers, guineas, regroups nosed lingers, proboscis monkeys, etc. All of these are confined to Asia, except the guineas which are an African variety.

They have no cheek pouches. The eschewal callosities are small. The thumb is reduced or absent. They have slender built bodies, short faces and long slender non- prehensile tails.

The semnopithecinae are distinguished from the cercopithecinae by the presence of maculated stomach (well adapted to digest food consisting mostly of leaves) and the absence of cheek pouches.

The Old World Monkeys differ from the New World Monkeys in having the following characters:

External Characters:

1. All species possess Ischia callosities.

2. All digits are provided with more perfectly flattened nails.

3. The thumb and the great toe are more highly specialized and are capable of more independent and individual movements.

4. The nostrils are situated close to each other

5. The tail is not prehensile.

6. The semnopithecinae have maculated stomach and the cercopithecinae cheek pouches.

Internal Characters:

1. The Bergman is placed relatively far forwards.

2. The pre-maxilla is extended up to the nasal opening. Sometimes it touches the frontal bone.

3. The jural never articulates with the parietal bone.

4. The palate is relatively long.

5. The postcranial axis is comparatively short.

6. The auditory bulla is absent.

7. The tympanic annulus is elongated and it forms an external auditory meats.

8. The dental formula is 12/2: Cl/1: PM2/2: M3/3, i.e. the premolars is two in number.

9. The upper premolars are three rooted and the lower two rooted.

Anthropoid Apes:

The anthropoid apes are represented by four main types: (I) Gibbon, (II) Orang­utan, (III) Chimpanzee, and (IV) Gorilla. They are tailless creatures and by this they are distinguished from most of the lower primates. They do not possess cheek pouches and eschewal callosities (excepting the gibbon) and in this character they differ from the Old World Monkeys. They are big-brained, flat-cheated and long-armed animals.

This group consists of two families, namely, Hylobatidae and Pontiac. The former includes the gibbon and the latter the orangutan, gorilla and chimpanzee.

(i) Gibbon:

The gibbon family includes two groups: Hypoblasts or the gibbon proper and the Symphalangus, the seaming.

Distribution: The seaming which is represented by only one species, is found only in the island of Sumatra, while the gibbons, comprising several species, are distributed in various parts of South eastern Asia, including North­east India and Burma, and also in many of the islands of the Indo-Malayan archipelago.

The gibbons are the smallest of the apes in size. Average weight of an adult common gibbon is 13 pounds, while that of the seaming is about 24 pounds. In erectly standing position their height does not usually exceed 3 feet.

They live in small families consisting of parents and minor children. They live on leaves, flowers, and fruits and on insects. Bird’s eggs and young birds are also eaten by them.

The gibbon possesses such long upper extremities that when it stands erect the finger-ups touch the ground. The extraordinary length of arms is directly associated with the brachiating mode of locomotion followed by gibbon about 90 percent of time. On the ground the gibbon may walk in the upright position using his arms for balancing.

The skin colour is usually black. The whole body except the face and eschewal callosities is covered with fine woolly hair. The head is narrow and elongated. The digits except the thumb which is imperfectly opposable bear elongated and laterally compressed nails.

The foot is also long and narrow. The great toe is set far apart from the other digits and is capable of wide range of movement. The digital formula, both in manus and pes, is typically, 3>2>4>5>1.

The cranium is enlarged and somewhat flattened, while the facial portion is reduced in size. The cranium presents ovoid contour and low frontal elevation. The orbits are large and prominent; the supraorbital torus is absent.

The nasal bones are flat and broad. The nasal aperture is ovoid. The mastoid and the styled processes are not developed. The globoid fosse is shallow the post globoid tubercle is well developed.

The Bergman is situated far back on the roof of the cranium. The dental characters show sexual differentiation. The canine is large, sharp and pointed and it interlocks on closure of the jaws.

The common gibbons differ from the seaming in some characters, e.g. seaming is larger than a gibbon, it has shorter legs and longer arms, trunk is relatively shorter and thick broader, the skull is longer and the cranial capacity is larger, webbing of the second third toes is more advanced; it has a laryngeal air-sac.

The skull of a gibbon is distinguished from that of other anthropoid apes by its abseil smaller size. It differs from that of the lower anthropoid by the absence of two transfuse ridges crossing the crowns of the molar teeth. It may be differentiated from that: cercopithecidae which has longer nasal bones and smaller skull with lesser cranial cape

(ii) Orangutan:

The orangutan is confined to the islands of Sumatra and Borneo anal represented by only one species. They measure about four feet in height from the vertex soles. The male members are heavier than the female members, the average weight being pounds in the former and 80 pounds in the latter. They are arboreal animals. Their movemeif are said to be very slow and deliberate. On the ground they go on all fours. The orangutan is very often described as slow, sluggish and morose creatures.

Their diet consists of wild fruits, leaves and shoots. It has been observed that they live families consisting of a male, female and their young children.

Long, coarse, shaggy hairs are sparsely distributed on their body. The hair colour is usually reddish-brown. Face, ears, soles and palms are naked. The skin colour is brownish; the nostrils are oval or slit-like in outline and are placed obliquely.

In profile the nose gives a flat, concave appearance as the root is narrow and the bridge is not elevated. The faces concave in profile. Such a condition of face is described as ‘sinognathism’. The ears an small. The hand is long and narrow, the fingers, except the thumb which is much short, an elongated. All the digits bear flat nails. The digital formula is 3>4>2>5> 1.

The foot is also long and narrow. The great toe is very small and is opposable. The upper extremities are very long. So when an orangutan is kept in crest posture the finger-tips reach the ankles.

The skull is distinguished by its relatively small braincase and enormous facial portion. The average cranial capacity of the male is 416 cc. The supraorbital ridges are not continuous and as such no torus is formed. The forehead is high and rounded.

The nasal bones are extremely small and these are fused together even in the young animals. The mastoid process is not developed. There is no styled process. The globoid fosse is shallow and the postglenoid tubercle is large. The external auditory meats are not much prolonged.

The jaw is of enormous size and is projecting. The chin is absent. The dental characters show sexual differentiation. The canines are long, sharp, and tusk-like and are interlocking.

They have 12 pairs of ribs as in man, as against 13 pairs in the gibbon, gorilla and chimpanzee.

The skull of an orangutan is distinguished form that of a gibbon by its absolute larger size. It differs from those of the gorilla and chimpanzee by (a) the large jaw in relation to the skull; (b) splint-like nasal bones and sinognathous face; (c) non-continuous supraorbital ridges.

(iii) Chimpanzee:

The chimpanzee includes three species the common chimpanzee, the bald- headed chimpanzee and the pygmy chimpanzee. They are found in the tropical forests of Africa.

The average height of the males is estimated at five feet and that of females at four feet. The average weight of the males is 110 pounds and of the females 88 pounds.

They live in small bands of about eight or nine individuals. Their food consists of various kinds of fruit and similar other vegetable products.

The chimpanzees are expert in climbing and brachiating. They run about on all fours. But they are capable of standing and walking erect.

The body is somewhat sparsely covered with long, coarse, shaggy hair of variable colours. The skin colour also varies. In the typical chimpanzees Chimpanzee the margins of the nostrils are not much expanded, and the ears are very large but without lobes.

The hand is elongated and narrow. The fingers are long, the thumb is opposable. The palm is naked. The foot is also long and narrow. The opposable great toe is set apart from other toes. The digital formula is 3>4>2>5>l both in manus and peps. The chimpanzees are sortilege and long armed animals. In standing position, finger-tips go down the knees.

The vault of the head is low. The cranial capacity of the male is about 400 cc. The supraorbital ridge is continuous and prominent but not as massive as in the gorilla. The nasal bones are much reduced in length and are fused in the early part of their life.

The nasal bridge is not elevated. The external auditory meats are prolonged and tubular. The globoid fosse is shallow in comparison to that in gorilla; the post-globoid region is well marked. The jaw projects forward. The chin is absent. The canines are large sharp and projecting but in a lesser degree when compared to those of gorilla and orangutan.

The chimpanzee skull may be distinguished from that of gibbon by its absolutely larger size. By way of differentiating it from that of orange the following characters may be noted:

In chimpanzee the supraorbital ridges are continuous, while these are discontinuous orange. In chimpanzee the nasal bones are not splint-like and the lower jaw is relating small. It differs from gorilla in having smaller skull with relatively larger cranium, into absence of prominent crowns and in numerous other details.

(iv) Gorilla:

The gorillas are inhabitants of western and east-central equatorial Africa. They comprise one genera and two sub-species, gamely, western coastal or lowland gorilla living in the Cameroons and the Gabon and eastern or mountain gorilla inhabiting the region of the eastern Congo, west of Lake Edward and Lake Kiou.

The gorilla has an enormously robust body weighing on average 450 pounds. The height ranges from 5 feet to 6 feet in lowland gorillas and 5 feet 3 VI inches to 5 feet 10’inches in mountain gorillas.

The gorillas pass most of their time on the ground. They very often climb tree also. Upon the ground their usual gait is obliquely quadruped though they can stand and walk era they walk upon the sole of the foot. They are slow-moving animals.

Their diet consists fruits, shoots, leaves and vegetables. They live in small bands of three to ten families. The skin colour is black or dark brown. The whole body, save the face, palms and soles is covered with black long coarse hairs.

The ears are small in size and bear no lobes. Themes shows slight elevation at the bridge but the root is low and flat. The nasal wings are van thick; nostrils are broad and directing forward. The lips are thin. The hand of the gorily resembles that of man in certain characters, e.g., it is comparatively shorter and broader to in other anthropoid apes, the thumb is also better developed. The foot of the gorilla adapted for arboreal pretension and it shows a tendency to resemble human foot.

The great toe is opposable and set apart from other digits. They are short-legged and long-armed creatures. When a gorilla stands the finger-tips reach below the knees. In proportion of the arm to the forearm the gorilla resembles man.

The head is very large but consists of smaller cranium and enormous and projecting fact and jaw. The supraorbital ridges are of enormous size and continuous to form a torus. The forehead is very low. The skull presents a very prominent capital crest which is weaker in female than in male. In body size also the females are smaller.

In some other charlatan including dental characters sexual differentiation is apparent. The average cranial capacity of the male is 550 c.c. and of the female 450 cc. The mastoid process is moderately develop.

The jaw is large. The chin is absent. The canines are of enormous size. All teeth are 1 more highly and more sharply cusped than those of the chimpanzee.

Careful examination yields many differences between the mountain gorilla and lowlands gorilla. For example, the former have a narrower skull, a large face, longer palate, shorter limbs, shorter and broader hand, larger trunk, narrower hips, etc.

How the skull of the gorilla may be distinguished from that of the gibbon, orange toll chimpanzee has already been stated in connection with the description of the respective groups.

(v) Hominidae:

In the absence of primarily bone, presence of chin and in many other details man differs from the cercopithecedac and the anthropoid apes and as such he could not be included under either of these families. Therefore, men constitute a separate family. Hominid with one genus Homo and a single species sapiens.

Some of the many distinguishing characters of man or true diagnostic characters of Homo as a type are as follows:

General Characters:

1. Bipedal walk.

2. Fully erect posture.

3. Larger size and complex character of brain.

4. Greatest weight at birth in relation to body weight in adult life.

External Characters

1. The density of hair (except on scalp) is reduced. Thus the body is relatively hairless.

2. Tactile hairs are completely absent.

3. The margins of the ears are highly-rolled.

4. The nose is prominent. The elevated bridge is formed by the nasal bones and the fleshy tip is supported by osteo-cartilaginous framework.

5. A median furrow or philtrum is present on the upper lip.

6. The mucus membrane of the upper lip is visible as the latter is outrolled.

7. Ischial collosities are absent.

8. The peculiar relation of the skin to the subcutaneous fat which is adherent to the former.

9. The legs are much longer than the arms.

10. The foot is arched both transversely and anteroposteriorly.

11. The great toe is the dominant digit while the lateral toes are reduced in size.

12. The great toe is not opposable; it is in the same line with the other toes and is under the common skin covering approximately up to the mid-point of the basal phalanx.

Skeletal Characters:

1. The cranium is enlarged and the face is reduced.

2. Shortest height of face.

3. The nasal bones are large and broad and they are separated by intra-nasal suture.

4. The premaxilla is never marked off from the maxilla by a suture.

5. The spheno-maxillary fissure is wide.

6. The external auditory meatus is relatively short.

7. In the orbit the lachrymal articulates with the ethmoid abone.

8. The sphenoid and the parietal bones are articulated at the side of the wall of the brain- box.

9. The ethmoid articulates with the sphenoid in the articular fossa.

10. The mastoid and styloid processes are well developed.

11. The foramen magnum is placed far anteriorly at the base of the skull so that the head is well balanced on the spinal chord.

12. The chin is present.

13. The simian mandibular shelf is absent.

14. No special sexual differentiation in the teeth is seen.

15. The upper molars are single rooted or double rooted.

16. The lower lateral incisors are broader than the central and the upper centrals are broader than the laterals.

17. The canines are small. Their crowns are almost at the same level with those of other teeth.

18. Diastema is absent in the dental series.

19. Highest average total number of vertebrae.

20. Highest average number of thoraco lumbar and coccygeal vertebrae except gibbons.

21. The lumbar curve of the vertebral column is fully formed.

22. Penis bone is absent.

23. The linea aspera in the femur is well marked.