Class Mammalia


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Mammalia Pre- Medical Presentation Diversity in Living World Dr. R. K Pillai, “Sneham”, Niranam North P.O., Thiruvalla – 689621, KERALA


2 Mammalia Number of species–5000 (living), Latin, mamma, breast. Mammology is the study of mammals. Mammals originated from the reptiles (Synapsid, Cynognathus ) in the Triassic period of Mesozoic era. Mammals are the dominated animals of Coenozoic, so this era is known as ‘age of mammals’. Cynognathus

General Characters:

General Characters Mammals are hair-clad,mostly terrestrial tetrapod vertebrates. Hairs of mammals are made up of a -keratin. Most important character of mammals is the presence of mammary glands (modified sweat glands). Body is distinctly divisible into head, neck, trunk and tail. Limbs two pairs, pentadactyl each with five or few digits. Limbs of mammals are adapted for walking, running, climbing, burrowing swimming or flying. Hindlimbs are absent in aquatic cetaceans and sirenians. Exoskeleton consists of lifeless, horny, epidermal hairs, spines, scales, claws, nails, hooves, horns, bony dermal plates, etc. Skin is richly glandular containing sweat and sebaceous glands. Presence of a muscular diaphragm separating thoracic cavity from abdominal cavity.

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Skull dicondylic with two occipital condyles (also in Amphibia). Each half of lower jaw with a single dentary bone. Vertebra with flat centrum called amphiplatyan or acoelous. Presence of seven cervical vertebrae. Coracoid of pectoral girdle is vestigial. Presence of 12 pairs of ribs (also 12 pairs of cranial nerves). Absence of cloaca (except in Monotremes). Teeth heterodont, thecodont and diphyodont. Respiration by lungs (pulmonary), glottis protected by a fleshy and cartilaginous epiglottis. Larynx with vocal cords. Heart completely 4-chambered (also in birds and crocodiles). Sinus venosus absent. Only left aortic (systemic) arch persists in adult.

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Renal portal system absent. Erythrocytes are small, circular and nonnucleated. Kidneys metanephric. Ureters open into a muscular urinary bladder. Excretion ureotelic. Mammals are the most intelligent animals among vertebrates. Brain highly developed with corpus callosum connecting cerebral hemispheres. Cranial nerves 12 pairs. External ear with ear pinna. Middle ear with three ear ossicles malleus, incus and stapes. Sexes separate. Testes mostly in scrotal sacs for sperm development. Ovary contains Graafian follicles.

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Eggs small, microlecithal, homolecithal, without shells. Mammals are viviparous, except egg-laying monotremes. Foetus nourishes through placenta. Placenta is formed by chorio-allantois. Extraembryonic membranes (amnion, chorion and allantois) present (amniota). Parental care greatly developed. Mammals are warm blooded (endothermal ) or homoiothermous animals with average body temperature 38 o C.


Classification Class Mammalia is divided into two subclasses, Prototheria and Theria. Subclass I PROTOTHERIA Prototherians are primitive mammals, egg laying mammals, oviparous mammals, reptile-like mammals, confined to Australian region. Young ones are fed on milk from mammary glands without nipples. Body temperature low 25-28oC. Prototherians are connecting link between reptiles and mammals. There is only one order under this subclass.

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Order Monotremata Mammals with single opening or cloaca. No external ear pinna. Testes abdominal, penis conduct only sperms. Uterus and vagina absent. Three examples of Prototherians are: Echidna (Tachyglossus) Spiny anteater found in Australia, New Guinea and Tasmania. Zaglossus Tachyglossus

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Zaglossus (=Proechidna) Ornithorhynchus, Duckbilled platypus found in Australia and New Zealand. Aquatic, found in rivers. Mammary glands are functional in both male and female. Platypus is the only poisonous mammal. Platypus

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Subclass II THERIA Subclass Theria is divided into two infraclasses: Metatheria and Eutheria. Infraclass I Metatheria Metatherians are pouched mammals young born in very immature state. Gestation short, complete development in the abdominal pouch or marsupium. Corpus callosum absent. Epipubic bones present. No allantoic placenta, teeth one set, monophyodont. There is only one order under this infraclass.

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Order Marsupialia Marsupials give birth to tiny immature young that crawl to a pouch on the mothers belly immediately after they are born. They attach themselves to milk secreting nipples nursing until they are mature enough to survive outside the pouch Two important examples are: Didelphis ( Opossum ) tree dwelling, found in America . Macropus (Kangaroo) found in Australian region. Locomotion in Kangaroo is saltatorial. Opossum Kangaroo

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Infraclass II Eutheria Eutheria includes viviparous placental mammals. On the basis of characteristics like skull, teeth and limbs, eutheria is arranged into 16 orders.

1. Insectivora:

1. Insectivora Smallest and most primitive eutherians. With long po9inted snout. Usually 5-toed with claws Molars with pointed, peg-like cusps for insect eating. Placenta discoidal. Noctural and terrestrial. e.g Talpa - Mole Sorex - Shrew Erinaceus - Hedgehog Shrew Hedgehog

2. Dermaptera:

2. Dermaptera Gliding mammals with patagium. e.g., Galaeopithecus (Flying lemur) Flying Lemur

3. Chiroptera:

3. Chiroptera Nocturnal,true flying mammals capable of echolocation, a type of radar system. Commonly called bats. e.g., Pteropus (Flying fox) fruit eating, frugivorous, Rhinolophus (Horse shoe bat) insectivorous, Desmodus (Vampire bat) sanguivorous Bat

4. Edentata:

4. Edentata Teeth absent or reduced to molars, without enamel.e.g., Dasypus (Armadillo) Myrmecophaga (Giant anteater) Bradypus (Sloth). Armadillo

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Anteater Sloth

5. Pholidota:

5. Pholidota Body covered with large overlapping horny scales, no teeth, tongue long and Protrusible, eat on ants. e.g., Manis (Pangolin or scaly anteater ) Pangolin

6. Rodentia:

6. Rodentia Largest order of mammals in number of species, small gnawing mammals. Each jaw with one pair of long rootless chisel-like incisors growing throughout life. No canines. e.g., Rattus (Rat), Mus (Mouse) Funambulus (Squirrel) Cavia (Guinea pig) Hystrix (porcupine) Dipodomys spectabilis (Kangaroo rat) is a desert rodent which never drinks water. Squirrel

7. Lagomorpha:

7. Lagomorpha Herbivorous with a second pair of upper incisors, no canines.e.g., Oryctolagus (Rabbit), Lepus (Hare) and Ochotona (Pika) Tailless. Rabbit eats its own faeces. Rabbit Hare

8. Carnivora:

8. Carnivora Predatory flesh-eating mammals. Fissipedia: Terrestrial carnivores Canis familiaris – Dog Felis domestica – Cat Panthera leo – Lion Panthera tigris – Tiger Acinonyx – Cheetah Lutra – Otter Herpestes – Mongoose Ursus arctos – Bear

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Mongoose Cheetah Lion Tiger

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Mongoose is an enemy of snakes. Lions are found in India and Africa. In India, lions are found in Gir forests of Gujarat. Tiger is the ‘National mammal of India’. Cheetah, Acinonyx jubatus , is the fastest animal on four legs, speed 70 m.p.h. Cheetah became extinct in India early in the present century. Pinnipedia: Marine carnivores,Stream-lined body, reduced tail, limbs modified into flippers. e.g., Odobenus (Walrus), Phoca (Seal) and Zalophus (Sea-lion)

9. Cetacea:

9. Cetacea Aquatic mammals, breathe by lungs. Blubber or subcutaneous fat present which helps in heat conservation. Skin glands absent. Forelimbs modified into paddle-like flipprs. No hindlimbs, no external ears. Testes abdominal. Hairs only on snout. Nostrils on the top of the head. Teeth often lost. Eyes very small. Bones spongy. Mostly gregarious and carnivorous.

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Blue Whale Dolphin

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Phocaena – Porpoise Orcinus – Killer whale Delphinus – Common Dolphin Platanista – Ganges Dolphin Physeter – Sperm whale Balaenoptera musculus (the blue whale) is the largest animal ever lived. Length 35 metres, weight 150 ton, feeds in arctic and antarctic waters on microscopic animals or plankton. Blue whale is the largest animal in the world living upon the smallest organisms, In whales, the milk is squirted down to the throat of baby by muscular contractions of mother. The Irrawaddy Dolphin ( Orcaella brevirostris ) is the flagship species of Chilika lake . Chilka is home to the only known population of Irrawaddy dolphins in India

10. Sirenia:

10. Sirenia Herbivorous aquatic mammals with paddle-like forelimbs, no hindlimbs, no external ears, no pinna, blubber present, testes abdominal. Rhytina – Sea cow Trichechus – Manatee Halicore – Dugong Manatus australis is a sea cow having six cervical vertebrae. Dugong Sea Cow

11. Tubulidentata:

11. Tubulidentata With tubular mouth, tongue slender protrusible, no incisor or canines, limbs clawed and adapted for digging ant and termite nests. Only example is Orycteropus (aardvark or Cape anteater of South Africa). Aardvark

12. Proboscidea:

12. Proboscidea Largest land living animals. Hairless skin (pachyderm). Nose and upper lip modified into proboscis. Two upper incisors modified as tusks. Hairless skin is an adaptationfor hot climate. Ivory is obtained from the tusk of elephant. Mammoths and mastodons were extinct elephants. Loxodonta africana – African elephant Elephas maximus – Indian or Asiatic elephant Elephas cyclotis – Pigmy African elephant

13. Hyracoidea:

13. Hyracoidea Small, guinea-pig like mammals distantly related to elephants. Snout, ears and legs short. 4 toes on front foot, 3 on hindfoot. Commonly called ‘African conies’.e.g., Hyrax (= Procavia ) from S. Africa, Syria and Arabia. African Cony

14. Perissodactyla:

14. Perissodactyla Odd-toed hoofed animals. Incisors present in both jaws. Stomach simple. A mule is a hybrid between male ass (jack) and female horse (mare). A hinny is hybrid betweenmale horse (stallion) and female ass. In India, Rhinos are found in Kaziranga National Park in Jorhat, Assam. Asiatic wild ass Equus hemionus is an endangered species, found in Little Rann of Kutch (Gujarat). Tibetan wild asses are found inhabiting Ladakh and nearby regions.

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Horse Donkey Zebra Malayan Tapir

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Equus caballus – Horse Equus asinus – Ass Equus zebra – Zebra Rhinoceros unicornis – Indian rhinoceros Diceros bicornis – African rhinoceros Tapirus indicus – Malayan Tapir

15. Artiodactyla:

15. Artiodactyla Even toed hoofed animals. Incisors and canines in upper jaw usually absent. Stomach 4-chambered. All except pig ruminate or chew their cud. Many with antlers or horns. Term ‘bovine’ is associated with Artiodactyla. Hippopotamus is called ‘Horse of the river’ found in Nile river of tropical Africa. Camels are well adapted for desert life and they are known as ‘Ships of the desert’.

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Hippopotamus Giraffe Camels Red Deer

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Hippopotamus amphibius – Hippopotamus Camelus dromedarius – Arabian camel Cervus – Red deer Giraffa camelopardalis – Giraffe Sus scrofa – Wild boar Bubalus bubalis – Water buffalow Kashmiri stag ( Cervus elaphus hanglu ), also called hangul, is a subspecies of Red Deer. It is the State Animal of Kashmir .

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Kashmiri stag ( Cervus elaphus hanglu )

16. Primates:

16. Primates Highest development of brain, most intelligent mammals. Mostly arboreal, first digit usually opposable, an adaptation for grasping. Eyes typically large and turned forward. Primates include lemurs, loris, tarsiers, monkeys, apes and man. Gibbon is the smallest man-like ape. Mandrillus is the African dog-like monkey. Chimpanzee is the most intelligent ape. Gorilla is the most powerful ape and is the largest living primate. Ateles (spider monkey) is found in South America (Mexico to Brazil). It has a prehensile tail which can be used as an extra limb to hang from trees, as a sensitive probe or to pick up an object.

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Lemur Tarsier

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Gibbon Gorilla Chimpanzee Orang-utan

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Ateles paniscus – Spider monkey Macaca mulatta – Rhesus monkey Macaca silenus – Lion-tailed macaque Hylobates lar – Gibbon Papio – Baboon Presbytis – Langur Pongo – Orang-utan Pan – Chimpanzee

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A true Objective Hand Book “A conscientious teacher of Zoology who has been guiding students for various competitions for last 30 years has put his best in this book” 13 th Edition

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