Division of the Chiroptera:
Two Suborders, Megachiroptera and Microchiroptera, are included under the Order Chiroptera. Besides the common chiropterian features, the suborders differ considerably from each other. The differences are tabulated in Table 45—Chordata.
Suborder Megachiroptera:
1. They are large in size among the chiropterans and frugivorous in habit.
2. Eyes are large and snout is elongated.
3. Tail is free from inter-femoral membrane.
4. Pinna is simple and leaf-like nasal or auricular appendage is absent.
5. The 2nd digit of the forelimb is always provided with claw except Eonycteris. Molars are devoid of sharps cusps, but are with longitudinal grooves.
Examples:
Pteropus giganteus (Flying fox) (Fig. 10.68B); Rousettus leschenaulti (Fulvous fruit bat); Cynopterus sphinx (Short-nosed fruit bat) etc.
Suborder Microchiroptera:
1. The order includes small and insectivorous forms.
2. Eyes are small and snout is short.
3. The first digit of the forelimb is provided with claw.
4. The tail, when present, is enclosed in the inter-femoral membrane.
5. The pinna is large and is provided with extra lobe inside, called tragus. There is also a lobe at the base of the outer margin of the ear, known as the anti-tragus. These organs seem to pick up high-pitched supersonic sounds.
6. Leaf-like auricular appendage on nose is present.
7. Molars are with sharp cusps and transverse grooves.
Examples:
Vespertilio, Rhinolophus and Desmodus (Fig. 10.68A). Desmodus is a vampire bat with an extra lobe in stomach. Indian Micro-chiropterans are represented by common yellow bat (Scotophilus heathi), pipistrelle (Pipistrellus coromandra), false vampire (Megaderma lyra), great eastern horseshoe bat (Rhinolophus luctus), etc.
Desmodus:
Desmodus or Vampire bat is found in South America. They are small bats. The snout is small. The first digit of the forelimb bears claw. The tail is present. Pinna is large with lobe, called tragus.
Foliaceous nose-folds around the nose are present (Fig. 10.68B). The molars bear transverse grooves. It is sanguinivorous and takes the blood of cattle by cutting the skin with its sharp bladelike upper incisors. The pyloric stomach bears a pair of sacs for storage of blood.
Order 4. Taenodontia (= Band teeth):
They are also considered as ‘orphan order’ and are all extinct. They were large animals of 30 cm or more in length. The limbs were clawed and strongly built. The teeth were long, rootless and were with little enamel.
Example:
Stylinodont.
Order 5. Tillodontia (= Tearing teeth):
The Tillodonts are considered as an ‘orphan order’ that evolved during Paleocene and Eocene from an insectivore stem and then became extinct. The size was large. They had strong skeleton with heavy and clawed feet. The skull had many similarities with the skull of rodents. The incisor teeth in both upper and lower jaws were large and chisel-shaped.
Example:
Tillotherium.
Order 6. Edentata [L. e, ex = without + dens, tooth] 30 species. Ant eaters, Sloths, Armadillos:
It is represented by polymorphic and geographically restricted group of mammals. Despite repeated taxonomic rearrangements the true affinities between the different members of the group is not clearly established.
1. The edentates, excepting the ant-eaters, possess teeth.
2. Incisors and canines are absent but molars are long and similar in appearance,
3. Enamel and root are absent but the pulp cavity is persistent.
4. A sticky tongue is present.
5. The zygomatic arch is reduced or absent.
6. The clavicle is present but the coracoid and acromion are fused.
7. Ischium is united with anterior caudal vertebrae.
8. Posterior thoracic and lumbar vertebrae are with additional pair of zygapophyses.
Suborder 1. Palaeonodonta:
The North American group was an offshoot from the ancestry that gave rise to Xenarthra. They existed between Paleocene and Oligocene. Metacheiromys of Eocene was about 45 cm in length. In all probabilities they lacked the dermal armour of armadillos but resembled them in finer details. The canines were covered with enamel but other teeth were reduced. Ischiocaudal symphysis and extra zygapophyses were absent.
Suborder 2. Xenarthra:
Despite great diversity of appearance and behaviour it forms a natural and exclusive group. All the members of Xenarthra belong to South America. Enamel in the teeth is lacking. The zygomatic arch is reduced or absent. Coracoid and acromion are fused. Additional pair of zygapophyses is present in the lumbar vertebrae. Ischio-caudal symphysis is present. Brain is simple and poorly developed. Testes are abdominal. The feet are clawed.
Infra-order (a) Cingulata:
Body is covered with horny scutes. Teeth are many. The jugal arch is complete. Many parts of the vertebral column are fused.
Superfamily: Dasypodidae:
The members have small but broad and compressed head. Number of digits in the forelimb varies from 3-5. The digits end in powerful claws. The digits on the hind limb are 5 in number but the claws are weakly developed. The tail is well-developed. An armour of bony dermal plates covers the dorsal part of the body.
The armour is divisible into three distinct regions. The anterior part is formed by closely knitted scapular shield, the middle part is formed by a series of transverse bands separated from one- another by hairy skin and the posterior part is formed by a pelvic shield.
Examples:
Armadillos of Central and South America (Chlamyphorous, Tolypeutes, Dasypus) (Fig. 10.69 A).
Infra-order (b) Pilosa:
Body is hairy. Teeth are much reduced. Jugal arch is incomplete. Parts of the vertebral column are not fused.
Superfamily: Myrmecophagoidae:
Members are represented by ant-eaters. The mouth is small and snout is elongated. Eyes are small. Forelimb has 5 digits. The 3rd digit is with powerful claw. Toes vary in number from 4-5 and are clawed. Body hairs are long. Tail is long and usually prehensile.
Examples:
The Great Ant-eater of S. America, Myremecophaga jubata (Fig. 10.70); the South and Central American Col lard Ant- eater, Tamandua tetradactyla.
Superfamily: Bradypodidae:
Members are with short and round head. Pinna is small. Limbs are long and slender. Forelimbs are larger than hind limbs. There are three digits in each limb. The digits are provided with long, curved and hook-like claws. Arrangement of hairs is opposite to that of other mammals. Algae grow on hairs to give a protective colouration.
Facial part is shorter than cranial part. Teeth are few in number, only 4-5 similar molars on each half of the jaw. Cervical vertebrae are 6-9 in number. Thoracolumbar are more than 19. Members are nocturnal, vegetarian, arboreal and solitary animals of slow habit. They are found in the rain forests of North and South America. Lethergic life is connected to the small size of thyroid and adrenals (Young, 1981).
Examples:
Bradypus tridactylus, 3-toed. Sloth (Fig. 10.69B), Choloepus didactylus (2-toed sloth). B. tridactylus (3-toed sloth) of S. America is the slowest mammal, which can move 3″-5″ per minute.
Order 7. Pholidota [Gk. Pholis = scale] 7 species. Pangolins:
The members of the order were included in the Order Edentata. But because of the morphological differences present between them a separate rank has been allotted to them. Most forms under this order are burrowing and terrestrial. They are found in Tropical Africa and Asia. They are primarily ant-eaters.
1. The body measures about 1.25 m. On the dorsal surface of head, body and tail horny epidermal scales are present in an imbricated fashion. Few hairs peep through these scales.
2. The ventral surface is covered with hairs.
3. The eyes are small and pinna is ill-developed.
4. The tail is long, tapering and prehensile.
5. The limbs are short but powerful.
6. There are five digits in each limb.
7. The digits are provided with claws.
8. The claws of the forelimb are curved and sharp.
9. Hind limb is plantigrade in nature.
10. The facial part is prolonged to form a short muzzle.
11. The tongue is long, sticky and protrusible and is retained in a sac. Teeth are absent.
12. The skull is long and cylindrical.
13. The orbital and temporal fossae are not separated.
14. Jugal is reduced.
15. The clavicle is absent.
16. The sternum is provided with cartilaginous rods which extend up to the pelvis.
17. They have the power to curl themselves like a armoured ball when they disturb.
18. They are ant and termite eaters.
Recent analysis indicate that the orders edentata and pholidota are the most primitive groups of living eutherian mammals (Kardong, 2002).
Example:
The Indian Pangolin (Manis crassicaudata, Fig. 10.71) and the Chinese Pangolin (Mariis pentadactyla). The Indian Pangolin is found in the plain and lower slopes of hills of India and Sri Lanka. The Chinese Pangolin inhabits in Assam, eastern Himalayas, Myanmar, and south China.
Order 8. Primates [L. Primus = first; Primate = one first in rank] 235 species. Lemur, Monkeys, Great apes and Man:
Primates meaning ‘first’ in latin, the name has given by Carolus Von Linnaeus. They are not so specialised as they are believed to be. The primates have retained many primitive and generalized eutherian characters and, at the same time, they show specialisation in some respects. The primates are primarily arboreal and return to land as a secondary condition. Primates are omnivorous in habit.
i) The body is covered ever with hairs except the palm, sole and parts of face.
ii) The neck is mobile.
iii) Forelimbs are shorter than hind limbs.
iv) Limbs have five digits and all the digits end in flat nail.
v) The pollex or thumb, hallux or first toe are smaller than other digits and are opposable (except the hallux of man).
vi) Locomotion is of plantigrade type.
vii) Tail is present in most forms.
viii) Brain is highly developed.
ix) The cerebral hemispheres are enormous, much convoluted and cover the cerebellum.
x) Neopallium and cortex are well-formed.
xi) Olfactory receptor organs, olfactory bulbs and rhinopallium are drastically reduced.
xii) The eyes are directed forward and the vision is binocular and stereoscopic.
xiii) Teeth show reduction in number.
xiv) Stomach is simple. Caecum is variable in size.
xv) Testes lie in scrotal sacs.
xvi) Mammae are two and thoracic in position.
xvii) Usually one young is born at a time and parental care is needed for a long period after birth.
xviii) The skull is more inclined to the vertebral axis.
xix) Orbital ring, is complete and the eye- socket is confluent with temporal fossa or is separated by a partition.
xx) Foramen magnum faces downward.
xxi) Zygomatic arch is complete.
xxii) The tympanic bulla is formed by a flange from the petrosal.
xxiii) The cheek teeth are of bunodont type.
xxiv) Clavicle is well-developed.
xxv) Radius and ulna move freely on one another.
xxvi) Lunar and scaphoid are distinct and well-developed.
Division of the Primates:
We shall follow here Simpson’s (1945) scheme from the book “The Life of Vertebrates” of J. Z. Young (1981).
There are two suborders:
(i) Prosimii
(ii) Anthropoidea.
Suborder (i) Prosimii (Palaeocene—Recent) [Gr. Pro = before + L. simia = ape]:
1. Primitive primates that retain insectivorous characters such as:
(a) Long face,
(b) Eyes are laterally situated,
(c) Orbit is widely confluent with the temporal fossa,
(d) A brain is smaller than anthropoidea.
(e) First upper incisors are separated in the midline,
(f) Mostly arboreal.
Fossils Record:
In the Palaeocene and Eocene they formed the whole order and they were distributed in Europe and North America. With the rise of Anthropoidea, their number of genera and species were reduced excessively.
Geographical Distribution:
Tropics of the Old World, extending from Africa, Madagascar to Philippine Islands.
The Suborder Prosimii is divided into 4 infraorders following Simons’ (1972) scheme.
1. Plesiadapiformes include the earliest primates.
2. Lemuriformes that include living lemurs of Madagascar and their fossil allies.
3. Lorisiformes and
4. Tarsiiformes, represented by a single genus of the East Indies. But Simpson (1945) divided Prosimii into 3 infraorders excluding the plesiadapiformes.
Infraorder 1. Plesiadapiformes (Cretaceous— Eocene):
It includes the four families. All are extinct.
Fam. 1. Paromomyidae:
i) The size of the animal was shrew-like and probably herbivorous.
ii) The molars were tritubercular. They are known from the late cretaceous and early palaeocene and occurred from the Purgatory Hill in Montana, U.S.A., e.g., Purgatorius.
Fam. 2. Plesiadapidae:
i) The body was squirrel-like but more heavily built.
ii) Chisel-like upper and large procumbent lower incisor. They were abundant in the Palaeocene and early Eocene, e.g., Plesiadapis.
Fam. 3. CarpoIestidae (Palaeocene—Eocene) e.g. Carpolestes
Fam. 4. Picrodontidae (Palaeocene) Picrodus
Remark:
Many recent authors like Simons (1964), McFarland et al., (1985) have included the tree shrews of South-East Asia as the first prosimians for the enlarged brains, and the first digit can be opposed to the others which heralds the hand, the prehensile organ, and reaches perfection in monkey, ape and man.
Infraorder 2. Lemuriformes (Palaeocene— Recent):
i) The muzzle is box-like with a cleft upper lip and is covered with hairs.
ii) The eyes are large but are directed somewhat sideways and most of the species contain only rods in the retina except Lemurs which are diurnal and contain cones.
iii) External ears may be large as in other nocturnal animals.
iv) Presence of a long tail.
v) The arms are much longer than the legs and the body is covered with soft woolly fur.
vi) The thumb and great toes are opposable to the other digits.
vii) The 2nd digit of the foot is provided with a pointed claw while the other digits have flat nails.
viii) The dentition of the lemurs closely resembles the insectivores. The number of teeth is 36. The incisiform lower canines lie alongside the procumbent lower incisors which are slightly separated and are used to peeling fruits. Dentition – I2/2, c1/1, pm3/3, m3/3 = 36.
ix) The uterus is duplex and placenta is non-deciduous.
x) Small cerebral hemispheres and uncovered cerebellum.
xi) The nose has 4-5 ethnoturbinal bones instead of the usual 3.
xii) Lachrymal foramen lies in front of the orbit.
xiii) There is a post-orbital bar but the orbit opens freely into the temporal fossa.
xiv) The orbits are directed laterally instead of forward.
xv) The nasal bones are large and wide at the back, instead of narrow and pointed.
xvi) They are generally nocturnal in habit.
Fossil Record:
At the beginning of Palaeocene and Eocene, they were spread all over the world. After the Oligocene period they began to disappear from Europe and America and at present the living forms are found only in Madagascar.
Division of the Lemuriformes:
Fam. 1. Adapidae (Eocene):
(i) The earliest lemur-like fossils come from the Eocene of Europe and North America and “were the first primates of modern aspect” (Simons, 1972).
(ii) They had more elongated snouts than present-day lemurs and smaller brains.
(iii) The incisors were not procumbent but the canines were incisiform.
iv) They mainly relied on smell rather than vision, e.g., Notharctus, Adapis.
Fam. 2. Lemuridae (Pleistocene—Recent):
i) Cat-sized quadrupeds and very similar in shape except variety of colours.
ii) Eyes are large and closely set.
iii) Long plumed or bushy tails longer than head and body.
iv) Upper incisors are separated by a wide diastema except Lepilemur which has no upper incisor.
v) Dental Formula = I0-2/2, c1/1, pm3/3, m3/3 = 32 – 36.
vi) Hind limbs longer than forelimbs.
Geographical Distribution:
Madagascar and Comoro Island.
Examples:
Five genera and fifteen species. The ringtail, Lemur catta (Fig. 10.72), widely known and is recognised by pale grey above, white below, with dark rings round the eyes and a long ringed tail. It is found throughout southern Madagascar to somewhat north of the Mangoky river.
They eat fruit and young leaves. They live in troops of about 12-15 animals including several males. The black lemur (L. macaco) is found in Nosy Be’ and the Sambirano.
The brown lemur (L. fulvus) is restricted to Madagascar and on the island of Mayotte. Hapalemur live in and feed on thickets of bamboo or in reed beds, leaping one vertical stem to another, keeping the body vertical. The commoner species is Hapalemurgriseus (Fig. 10.73).
It has three races. H. g. griseus has a uniform grey colour and ranging from 25-30 cm long. It is a crepuscular animal. They live in the eastern forest. They are monogamous and maintain a territorial ownership and their groups are small, usually 3-4. The western form, H. g. occidentalis, was discovered near Antsalova in 1972. The third race, H. g. alaotrensis, was discovered in 1968 in the Lake Alaotra.
The ruffed lemur, Lemur variegatus (=Varecia variegata), has thick woolly fur, with a white ruff. They live on the Masoalala Peninsula and in the eastern forest from Maroansetra south to the Mananora river. Sportive lemur, Lepilemur, a little grey animal, ranges from 25-35 cm including its head and body. They are nocturnal and consume only leaves.
They are distributed round Madagascar. Other lemurs are – the mouse lemur (Cheirogaleus pusillus) and the lesser mouse lemur (Microcebus murinus). The first of these is rat sized and a forest dweller and the second one is plains dweller.
Both are nocturnal and eat insects and vegetables. Young (1981) has included the mouse lemur and lesser mouse lemur under the family Lemuridae but Jolly, A. et al., (1984) have created a separate family – Cheirogaleidae for them.
Family 3. Indridae (Pleistocene—Recent):
i) Digits of the foot are united by a web of skin.
ii) The lower canines and one premolar in each half jaw are lost.
iii) All indris are leaf-eaters and move by vertical clinging and leaping.
Examples:
The woolly lemur, Avahi laniger, is grey-brown with rounded face. Head and body measure 30-33 cm. They live either alone or in couples arid are nocturnal in habit. They are monogamous and give birth to a single young. Sifaka, the genus propithecus has two species and some eight subspecies. They have short arms, long legs and tail. They are diurnal and like basking in the sun.
They consume leaves, fruits, flowers and barks. They live in groups of 3-11. P. virreauxi coquereli, (Fig. 10.74) a north-western sifaka is recognised by an all-white head but a maroon eagle-wing pattern on its forearms and thighs. There is one living species of Indris, Indri indri, (Fig. 10.75) which is the largest of all modern lemurs.
Head and body measure about 70 cm and its stumpy tail is just 3 cm. The Indris has a thick, silky fur, black back, hands and feet. Its limbs are mostly white. They live on vegetarian diet and are diurnal in habit. They are monogamous and the females carry a single young in July. They are confined to the eastern forest of Madagascar.
Family 4. Daubentoniidae (?—Recent):
i) It has large continually growing upper and lower chisel-like incisors.
ii) It has lost all its canines and most of the premolars.
iii) Dental formula = I1/1, c0-1/0, Pm1/0, M3/3 = 18 or 20.
iv) Presence of inguinal mammae except a pair of breast.
v) All the digits except the great toes bear claws.
vi) They possess enormously long third, digit by which it can extract insect larva from trees bark or from decaying wood.
Example:
The Aye-aye (Daubentonia madagascariensis) (Fig. 10.76) is the only member of this family. It is blackish-brown, with paler face and has huge mobile ears. They are nocturnal and lead a solitary life. They build twig nests. They inhabit the eastern coastal part of Madagascar (Malagassy Republic).
Status:
Only about 50, left in the Madagascar’s forest.
Infraorder 3. Lorisiformes (Miocene—Recent):
All the lorisiform animals are very like lemurs in their basic features except
i) They have no tails and the index fingers are vestigial.
ii) Vibrissae are reduced.
iii) A second pair of mammae in the inguinal region in addition to the normal pair on the breast.
iv) In some of them the face is shorter and the brain case is rounder than the true lemurs.
v) Lower canine is incisiform.
vi) They are nocturnal and slow mover, mainly spend life on trees.
Geographical Distribution:
Tropical regions of Africa, India, Sri Lanka and East Indies.
Content:
It includes a single family — Lorisidae with 6 genera and 11 species.
Examples:
The slow loris, Nycticebus coucang (Assam, Bangladesh, Myanmar (Burma) and the countries eastward) has short, thick limbs (Fig. 10.77), and the slender loris, Loris tardigradus (South India and Sri Lanka), has longer and slender limbs and snout more pointed.
The Potto, Perodicticus potto, and the Angwantibo, Arctocebus caiabarensis, are the African forest dwellers and much like the slow lemurs. They are nocturnal and strictly arboreal.
Bush-babies or galagos with several species are also African. The great Galago or Bush-tailed, Calago crassicaudatus of East Africa is 30 cm long and the tail is slightly longer. They are nocturnal, prowling at night in search of insects, fruits and eggs.
Infraorder 4. Tarsiiformes (Palaeocene— Recent):
i) The animal is rat-like in size of which the body is about 15 cm long and tail is about 25 cm.
ii) The tail is almost hairless except for the terminal tuft.
iii) Face is flattened and external ears are large and mobile.
iv) The limbs are elongated, specially the tarsal bones. The long and powerful limbs are used for jumping about in trees.
v) Both first digits are used for grasping and tips of digits are expanded to form adhesive pads. All have nails except the 2nd and 3rd in the hind-limbs which carry claws.
vi) The eyes are large and closely set. The ears and eyes are adapted for nocturnal habit.
vii) Dental formula = I2/1, c1/1, Pm3/3, M3/3 = 34.
viii) Cerebellum is small and simple.
ix) Ilium is very long like other jumpers.
x) Skull is rounded.
xi) Placenta is discoidal.
xii) They are nocturnal, arboreal and insectivorous.
xiii) Tarsier has the ability to rotate its head through 180 degrees. No other primate can manage more than 90 degrees.
Geographical Distribution:
Philippines, Sumatra and Borneo.
Content:
It includes two families:
(i) Anaptomorphidae (extinct) includes Tetonius and Omomysoi Europe and America,
(ii) Tarsiidae (Eocene—Recent). It includes 1 genus 3 species. Tarsier (Tarsius spp.) — East Indies. Tarsius bancanus is one of the three species, lives in the forests of South-East Asia.
Tarsier:
Tarsius (Fig. 10.78) is found in Indo-Malaya and Philippines. It is a small (about 6 inches = 15 cms) mammal with long pinnae. Eyes are large, protruding and directed forward. Hind limbs are longer than the forelimbs. The tarsus of the hind limb is elongated and, hence, the name of the animal is Tarsius. The limbs are with five digits and adhesive pads are present in the hand and foot.
It is nocturnal, insectivorous and lives in pairs in the hollows of the trees.
Suborder 2. Anthropoidea (Oligocene— Recent) [Gr. anthropos = man, oeides = resembling]:
i) The frugivorous primates that possess flattened, bare faces and forwardly directed small eyes.
ii) The external ears are small with the edge rolled over.
iii) Pollex and hallux are opposable and all the digits end in nails.
iv) The hands and feet are used for locomotion and feeding.
v) The mammae are always pectoral.
vi) The orbit is completely separated from the temporal fossa.
vii) Presence of a bony external auditory meatus.
viii) Incisors do not exceed two in each jaw, become spatulate rather than pointed.
ix) The two mandibles are united by symphysis.
x) Presence of menstrual cycles throughout the year except New World monkeys where the cycle is not well represented.
xi) Monkeys except marmosets give birth a single baby at a time. The babies are helpless after birth and they can cling to the mother.
xii) They are diurnal in habit. They have also colour perception than prosimians.
Content:
The suborder Anthropoidea is divided into 3 super-families:
(i) Ceboidea
(ii) Cercopithecoidea
(iii) Hominoidea. Simpson (1945) lists 66 genera under this suborder of which 30 are extinct.
Superfamily 1. Ceboidea (New World monkeys) (Miocene—Recent):
i) They are flat-nosed American monkeys (New World), formerly known as platyrrhini (broad-nosed).
ii) They have bare, flattened faces with small eyes.
iii) There are two pectoral mammae.
iv) Facial vibrissae are present but usually small.
v) Their thumbs are usually degenerated and tails are long and usually prehensile.
vi) Nostrils are widely separated.
vii) They possess three premolars in each half of both jaws and twenty-four milk teeth.
viii) There is a large tympanic bulla.
ix) No cheek pouch.
x) All are arboreal in nature.
Geographical Distribution:
South America.
Content:
It includes 2 families including 14 genera.
Family 1. Callithricidae (Recent): Marmosets and tamarins:
i) They are squirrel-like in appearance.
ii) Dental formula I2/2, c1/1, Pm3/3, M2/2 = 32
iii) All the digits bear pointed claws except thumb which has a flat nail.
iv) The tail is not prehensile.
v) Face is naked.
vi) They are strictly diurnal and arporeal.
vii) They are either frugivorous or insectivorous.
Geographical Distribution:
Neotropical.
Content:
It includes 4 genera and 33 species.
Examples:
Marmoset (Callithrix); Common Marmoset (C. jacchus) is an inhabitant of Amazon. Lion Marmoset (Leontocebus leonicus) inhabits the Amazon basin. Tamarins (Mystax) are related forms of marmosets. The pigmy marmoset of Ecuador in South America is the smallest of all monkeys and apes which is about 4″ long including tail and weight about 60 gm. The golden lion marmoset is the rarest form of all monkeys found in Latin America.
Family 2. Cebidae (Miocene—Recent) New World monkeys:
i) Body is slender with nails on all digits.
ii) Dental formula I2/2, c1/1, Pm3/3, M3/3 = 36.
iii) Nostrils are well separated by a broad interonarial cartilage.
iv) Tail is prehensile and long in the titis and sakis but short and nonprehensile in uakaris.
Some are nocturnal.
Geographical Distribution:
Neo-tropical.
Content:
It includes 11 genera with 29 species.
Examples:
Capuchin monkeys (Cebus), Spider monkeys (Ateles) (Fig. 10.79), Howlers (Alouatta), Titis (Callicebus), Sakis (Pithecia and Chiropotes), Uakari (Cacajao), Squirrel monkeys (Saimiri), Woolly monkeys (Lagothrix) etc.
Superfamily 2. Cercopithecoidea (Oligocene —Recent) Old World monkeys:
i) Nostrils are closer together than in Ceboidea and point downwards.
ii) The thumb is usually opposable.
iii) Narrow nasal septum.
iv) There are only two premolars in each half of both upper and lower jaws.
v) They have often internal cheek pouches.
vi) Tail never prehensile.
vii) Dental formula: 2.1.2.3/2.1.2.3 = 32.
They are often called Catarrhina or narrow-nosed primates.
Geographical Distribution:
All the warmer zones of the eastern hemisphere except Madagascar and Australia.
Content:
It includes two families.
Family 1. Parapithecidae:
(Oligocene) – Extinct, e.g., Parapithecus.
Family 2. Cercopithecidae (Miocene—Recent):
Found in Africa and Asia. It includes 11 genera and 60 species.
Examples:
Langurs, Presbytis (Fig. 10.80 A-D) are inhabitants of India, Sri Lanka, Tibet, Java, Borneo and Sumatra. Presbytis has rudimentary thumbs and there are no cheek pouches; the macaques or rhesus monkey (Macaca) (Fig. 10.80E-F) of India, Myanmar, China, Japan, Malay, North-Africa and Jibraltar; Baboon (Papio) of Africa; Mandril (Mandrillus) of Africa; Guereza, (Colobus), Africa; Pigmy Ape or Barbary Ape (Macaca inua) which is almost tailless and has a long snout and found in Morocco and Algeria; the Guenons (Cercopithecus), found in Africa.
Superfamily 3. Hominoidea:
There is a large brain-case and definite forehead.
Content:
It includes two families.
Family 1. Pongidae (Apes) (Oligocene—Recent):
i) The arms are longer than the limbs and they have no tail.
ii) During walking, the palms are never applied to the ground but the knuckles (finger joint) or the bent fingers touch the ground.
iii) Foot is more suited for walking.
iv) Hands are specialised for brachiation, especially in the gibbons.
v) More or less upright posture.
vi) Chest is more wider and neck is more longer as compared with monkeys.
vii) The canines are often large, especially in males.
viii) Molars bear grinding tubercles.
ix) Dental formula, 2.1.2.3/2.1.2.3 = 32.
x) There is a higher degree of development of brain.
Geographical Distribution:
Confined to Africa and South East Asia. It includes 4 genera and 8 species.
Examples:
Gibbons (Hylobates) (Fig. 10.81 A) are found in the forests of Assam, Myanmar, China, Thailand, Malay, Sumatra, Borneo and Java. The genus Hylobates includes Hoolock Gibbon (H. hoolock), the Lar Gibbon (H. lar), the Black Gibbon (H. concoloi) and the Siamang (H. syndactylus). Hoolock gibbon is the only ape found in India. The gibbons are slender, 90-95 cm in height and 15-25 lbs in weight. The arms are longer than the limbs and also can touch the ground.
They are the only apes which can walk erect, using the outstretched arms as a balance. They are very agile and spend chanting in chorus from morning till night. They are normally frugivorous and herbivorous but often eat insects, spiders, bird’s eggs and small vertebrates.
They attain sexual maturity between 5 and 8 years. Mating time is early in the rainy season and gestation lasts about seven months. Among the apes they possess a large brain in proportion to their body weight but they are less intelligent.
Orang-utangs [Pongo pygmaeus] live in the forests of Sumatra and Borneo. They are 135 cm in height and weigh about 150 lbs. The body is covered with mahogony-coloured hair. It is the only anthropoid which has developed arched forehead (Fig. 10.81 B). Much less agile than the gibbons and eat mainly buds and fruit. Its cranial capacity is midway in between gorillas and chimpanzees and the brain is very near to man’s.
There are two species of Chimpanzee (Pan) (Fig. 10.81C). Pan satyrus lives in the West Coast of Africa across the Great Lakes east of the Congo. Another species is Dwarf Chimpanzee (P. paniscus) which lives in the south of Congo river.
The Chimpanzee is the most intelligent of all the apes and the brain even possess the gyrus of Broca, the centre of articulate speech.
Gorilla (Fig. 10.81D) is recognised by a single species (Gorilla gorilla) which lives in the deep forests of Cameroon, Gabon, and Congo.
The Mountain Gorilla which is sometimes regarded as a subspecies (G. gorilla beringei) is more fully terrestrial and is found in the mountains north of Lake Kivu and on the Uganda border.
Lowland gorilla (C. g. graueri) is found in the dense forest of the Hante Sanga Prefecture of south western central African Republic. It is the biggest of the apes and the adult male is about 6′ tall and weighs abount 200 kg. The sexual maturity attains at the age of 12.
Family 2. Hominidae (Upper Miocene— Recent), Man:
i) The members are well-adapted to a bipedal gait.
ii) The Pollex (the thumb) is opposable but not the hallux (the great toe).
iii) The canine is relatively small.
iv) The number of teeth is 32.
v) Presence of lumbar curve on back.
vi) Omnivorous.
Fossil Record:
Several fossil forms of hominids have been found in the Miocene and Pliocene of India, Asia, Africa and Europe (Ramapithecus = Kenyapithecus). Australopithecus collected from the Pliocene — Pleistocene of the south and east Africa.
Geographical Distribution:
Cosmopolitan.
Content:
One genus and one living species.
Examples:
Modern man (Homo sapiens sapiens). The differences between the Lemuriformes, Tarsiiformes and Anthropoidea are shown in Table 46.
Table 47 shows the differences between the two divisions:
(1) Face is bare, flattened,
(2) Face is covered by hairs (Fig. 10.82).
Catarrhina includes macaque and hanuman among many Indian forms. Table 48 shows the differences between the two forms.
Evolutionary significance of Primates:
The primates include three distinct groups: Lemuroids, Tarsioids and Anthropoids. These three groups exhibit an evolutionary sequence from lowly to highly developed condition.
Lemurs—occupy the primitive rank:
The suborder Lemuroidea shows many distinguishing features which are most primitive.
These primitive features are:
(1) Low brain-case with its macrosmatic brain and uncovered cerebellum.
(2) Backward extension of jugal.
(3) Epicondylar foramen in humerus and the third trochanter in femur are present.
(4) Laterally placed eyes.
(5) Dentition is on the primitive trituberculo-sectorial plan.
Tarsioids—form the intermediate link:
The tarsioids occupy an intermediate position between the lemurs and anthropoids. The lemuroid features are the presence of extra-orbital lacrymal foramen and retia mirabilia.
But the tarsioids are more advanced than lemurs by having:
(1) Forwardly placed eyes.
(2) Microsmatic brain.
(3) Femur with third trochanter.
(4) Jugal does not extend backward.
Anthropoids—occupy the highest rank:
The position of anthropoids in the highest rank amongst primates is indisputable, because the anthropoids possess the following characteristics:
(1) Forwardly directed stereoscopic eyes.
(2) Absence of retia mirabilia.
(3) Clitoris is not traversed by urethra.
(4) Advanced brain with cerebellum covered by cerebrum. Both have a large number of convolutions.
The evolutionary development of the order primates and its phylogenetic relationship with other mammals is far from complete because of the rarity of preservation of the arboreal skeleton.
From the scanty fossil evidences and also from the surviving forms, the prime evolutionary trend is the gradual increase in size and complexities of brain, specially the neopallium. The development of brain is largely due to the acquisition of an opposable thumb and a grasping hand that enable them to bring the objects before the eyes for examination.