Class Mammalia
Mammals were evolved in Triassic period of Mesozoic era. Coenozoic era is golden era of mammals.
Study of mammals is known as Mammology.
Main Characters:
The members of this class are cosmopolitan.These are highly developed animals.
Body is divided into head, neck, trunk and tail.
A horizontal, diaphragm is present in the body cavity of all the members of this class without any exception.
This diaphragm is present in between thorax arid abdomen.This helps in respiration, defaecation, micturition arid parturition.
Their body is covered by a coat of hair (made of a Keratin), called pelage.
Skin of mammals is thick, water proof, glandular. So many types of glands are present in the skin as sweat glands, oil glands or sebaceous glands and mammary glands.
Mammary glands (Modified sweat glands) are found in females for baby feeding, so on the basis of this/ the class mammalia was so named.
Mostly horns are present at head, nails at digits, claws or hoof are found/ which provide protection.
Two pairs of limbs are present in trunk. Limbs are pentadactyle which help in swimming, walking/ running etc. Hind limbs are absent in Cetacea and Sirenia.
Alimentary canal is complete, its proximal end is called mouth and distal end is called anus. Anus and urinogenital apertures are separate. Cloaca is absent (Exception-members of Prototheria have cloaca)
Teeth are fixed in sockets in the buccal cavity, so teeth are called Thecodont.
Teeth are of four types i.e. such type of teeth are called Heterodont teeth.
Teeth come out two times in a life span in most of the animals so these are also called diphyodont teeth.
Suspensorium of their jaws is craniostylic type.
Lower jaw is made up of dentary bone.
Respiration is by one pair of lungs (Enclosed in pleural cavity).
Larynx or sound organ is found in the neck region for the production of sound.
Heart four chambered. Double circulatory system is present. No sinus venosus. Only left aortic (systemic).
RBCs small, circular and non nucleated except, family camilidae (Lama) and Camel which has nucleated RBCs.
Endoskeleton is bony, skull is dicondylic.
Vertebrae are acoelous or amphiplatyan type i.e. centrum is flat at both the sides. Cartilaginous pads are found at the edges of centrum, that are called epiphysis.
Neck is having 7 cervical vertebrae except:
Bradypus/sloth has 9 or 10 cervical vertebrae and Sea - cow / mantees has 6 cervical vertebrae.
Ribs are bifid.
One pair of Metanephric kidneys are situated in abdominal cavity. These animals ate ureotelic.
Brain is comparatively large and highly developed.
Cerebrum and Cerebellum are very complex in structure and highly developed.
A special structure is present for the connection of both the cerebral hemispheres of brain, that is called corpus - callosum. (Absent in Monotermes & Marsupial)
Optic lobes are four in number and are solid. All the 4 optic lobes collectively known as corpora quadrigemina.
Cranial nerves are 12-pairs
External ear is present in the form of ear pinna.
Malleus, Incus and stapes are the three ear ossicles in middle. ear.
Cochlea of internal ear is highly coiled spirally.
Mammals are unisexual animals. Testes of males are situated (outside the body) in the scrotal sacs. A distinct penis is present in males for copulation,
Ovaries and a reduced penis clitoris is found in females.
Fertilization is internal and it takes place in fallopian tubes.
Eggs are developed in uterus. Embryonic membranes amnion, chorion and allantois and yolk sac are found in embryo so these are grouped under group Amniota.
Eggs are alecithal or microlecithal & homolecithel but eggs of prototherians are megalecithal.
Embryo is attached through the uterus of mother by placenta, so these animals are also called placental animals.
Placenta helps in the nutrition, respiration and excretion of embryo.
Mostly mammals are viviparous, which give birth to their young ones. Some mammals are oviparous [Prototherians], some mammals are ovoviviparous. [Metatherians].
Parental care is well marked in mammals. Mother feeds the child by milk secreted by her mammary glands and looks after her child.
Mammals are warm blooded and. homeothermic or endothermic animals
Livings mammals are classified into two subclasses
Subclass: Prototheria
In this subclass primitive egg laying mammals are included.
Eggs are large, yolky and shelled. (Megalecithal)
Mammary glands are without nipples.
Gynaecomastism is found in these animals i.e. male and female both feed their child. Mammary glands are functional in males and females Doth.
Cloaca is present.
Testes in males are situated inside the body (abdominal cavity)
Pinnae are absent and cochlea is less coiled.
Corpus- callosum is absent in brain.
A toothless horny beak is found in adult animals, but teeth are present in child hood.
These are partially homeothermic animals
Members of this subclass are found in Australia, Newguine and Tasmania.
Only one order is included in this subclass.
Order - Monotremata
Connective links between reptiles and mammals.
e.g..
Ornithorhynchus or Duck billed platypus- poison glands are found in male platypus.
Tachyglossus or Echidna or spiny anteater.
Subclass - Theria
These are viviparous animals.
Embryo is attached with uterus of mother by placenta.
Mammary glands with Nipple
Cloaca absent
Testes are situated in scrotal sacs.
Pinnae are present and cochlea much coiled.
Corpus collosum present
Teeth are present
Teeth are found in adult and children both.
Subclass Theria is subdivided into two infra classes
(A) Infraclass - Metatheria or Marsupials
An abdominal pouch called marsupium is found in these animals, in which immature young ones are developed till maturity.
Mammary glands are present and nipples are also found on these mammary glands, these are situated in marsupium.
Penis is bifid, two vagina, two clitoris and two uteri are present in a female animal.
Yolk sac, placenta are found.
Cochlea is more coiled in internal ear.
Teeth are present in adult animals, which are monophyodont and heterodont type.
Corpus callosum is also absent.
Only one order is included in this infraclass.
Order - Marsupialia
Characters like metatheria Animals are ovoviviparous e.g.
Macropus-Kangaroo-Found in Australia only.
Saltatoriall ocomotion (Tail to use as body balance)
Didelphys - Opossum - Found in North America.
Shortest gestation period (12-13 days).
Dasyurus - Tiger cat.
These are true mammals, that give birth to a mature child. A true placenta is found, which is allantochorionic type.
Nipples are well marked in mammary glands.
Uterus and vagina are single i.e. only one uterus and only one vagina are present in a female. Penis simple.
Cochlea is highly coiled.
Corpus callosum is found in brain.
Completely endothermic animals.
Infraclass Eutheria is divided into 16 orders
Order (1): Insectivoral
These are burrowing nocturnal and insectivorous animals.
e.g.
Erinaceous - Jhau - Chuha/Hedge Hog
Sorex - Shrews: smallest mammals size is about 3- inches:
Chhachhunder
Talpa - Mole
Order (2): Dermoptera/Flying lemurs
In this group, all the false lemurs are included, which do not fly.
These are fruit eaters (frugivorous)
e.g.Galeopithecus - Flying lemur.
Order (3): Chiroptera
In this group bats are included which can fly in air.
These are true flying mammals.
Skin between forelimbs and hind limbs is expanded in the form of patagium, it works as wing, which helps in flying.
Testes are inside abdomen.
Ecolocation (Radar system) sensory system. e.g.
Pteropus - Flying fox, It is a fruit eater animal.
Vespertilo - Insectivorous bat, it is also called filtter mice.
Desmodus - Vampire bat, it is a sanguivorous animal
Order (4): Rodentia
It is the biggest order in mammals.
These are small, terrestrial, herbivore or omnivore animals.
Incisor teeth grow continuously in these animals and canines are absent, empty space of canine is called diastema.
e.g.
Order (5): Edentata (Ant - eaters)
These are insectivore animals, tongue of these animals is long, thin and sticky.
Digits are clawed.
Teeth ill developed or absent.
It is the only mammal, which has exoskeleton of bony plates or horny scales.
e.g.
Myrmecophaga - Giant ant eater.
Dasypus or Armadillo - It shows polyembryony (4-8 embryoes)
Bradypus - Slowest animal
Order (6): Pholidota (Scaly ant-eater)
Teeth are absent. Tongue is long. e.g.
Manis/pangolin - Scaly ant eater
Order (7): Lagomorpha
Rodent like mammals
Complete herbivore
Canines absent, diastema is present
e.g.
Order (8): Carnivora
Canines well developed.
Smart, strong and carnivore animals.
Upper last premolar and lower first molar are meant for tearing the flesh these are called carnassial teeth.
Digitigrade locomotion.
Terrestrial carnivores animals are called Fissipedia & Marine carnivores are called Pinnipedia.
Digitigrade animals
e.g.
Canis familiaris - Domestic dog.
Felis domesticus - Domestic cat
Panthera leo - Lion - Lions in Irrlia are found only in Gir forests of kathiawar of Gujrat state.
Panthera pardus - Tendua - Panther.
Pantherd tigris - Tiger - It is the National animal of India.
Acinonyx - Cheetah - It is the extinct animal of India.
Vulpes - bengalneneis - Fox.
Zalopus - Sea lion.
Phoca - Seal.
Herpestes - Mangoose.
Ursus - Bear.
Canis lupus - Wolf.
Order (9): Cetacea
These animals are fish like marine mammals
Hind limbs absent.
Hairs & Pinnae are absent.
Testes found in abodmen.
A thick heat resistance layer of adipose tissue is present just beneath the skin, that is called blubber.
e.g.
Balaenoptera musculus - Blue whale - Found in
Antartic ocean. A horny sheet called of Baleen plate (for filtration) is found in upper jaw instead of teeth.
Milk is squirited to through of baby by the muscle contraction of mother. Retea mirabile is found in thoracic region which helps in respiration in under water.
Phocaena porpoise - Small whale
Orcinus - Killer whale.
Caparea - Pigmy whale.
Physeter - Sperm whale - From its intestine Ambergis is secreted which is used in making perfumes.
Platanista gangatica-Dolphin - It is found in Ganga river.
Order (10): Sirenia
Herbivorous aquatic animals.
Hind limbs absent.
Pinnae absent.
A transverse fin on tail. Big tusk in male.
e.g
Rhytina - Sea cow
Trichechus - Manatee
Halicore - Dugong
Order (11): Tubulidentata
Tubular mouth, Tongue Slender & Protrusible. e.g.
Orycteropus - Aardwrark - It is found in Africa.
Order (12): Proboscida
This order includes .largest and heaviest modern terrestrial animals.
Upper incisors long, tubular form tusks. Canine absent.
Molar teeth are lophodont type.
Hair less, Testis found in abdomen. e.g.
Elephas - Indian elephant
Loxodonta - African elephant, it is largest living land animal.
Order (13): Hyracoidea
Small herbivore animals like rabbit
Plantigrade animals
e.g.Hyrax - It is found in Asia and Africa.
Order (14): Artiodactyla
Stomach is four chambered, it helps these animals in ruminating (Cud-chewing).
All animals are Ruminant except pig and Hippopotamus [Nonruminant). Even toed ungulate animals.
e.g.
Bos indicus - Cow
Bubalus bubalus - Buffalow
Camelus - Camel [RBC nucleated]
Sus - Pig
Capra - Goat
Ovis - Sheep
Bos mutus/Poephagus - Yak
Cervus - Dear
Cameloparculelis - Girrafe
Moschus moschiferus - Musk dear (Smallest RBC)
Order 15: Perissodactyla
Limbs long which have 1 or 3 digits with hooves.
These are fast runners.
Odd toed animals
e.g.
Equus caballus - Horse
Equus asinus - Donkey
Equus hemionus - Indian Donkey
Equus zebra - Zebra
Rhinoceros unicornis - Rhino - Single horn Genda. It is found in Kaziranga National Park Jorhat, Assam. Rhino psosses keratin horn over snout.
Order (16): Primates
Most developed mammals. It includes wise or most intelligence animals e.g. man, monkeys, lemur, apes, gibbons, gorilla, chimpangee etc.
Cerebrum highly advanced.
(a) Prosimians
e.g.
Nycticebus - Lemur
Loris - Loris (tailless)
Tarsius - Tarsier
(b) Simians
e.g.
Macaca mulalta - Rhesus monkey
Hylobates - Gibbon - smallest ape. (found in India) Only ape found in India - Hoolock gibben
Gorilla - Largest ape.
Pan Chmipanzee - Most intelligent in apes.
Oranguttan - Man of forest (found in Indonesia)
Homo-sapiens - Man
Review
Mammalia (mammals): Skin with sweat and milk glands, and with hairy coat that conserves body heat, four limbs having digits armed with claws, nails or hoofs, buccal cavity with thecodont, heterodont, diphyodont teeth, spongy elastic lungs, heart 4 chamered, cerebral hemispheres connected together by corpus callosum, optic lobes divided into four corpora quadrigemina, external ear often with pinna, males with copulatory organ, eggs amniotic, fertilization internal, no larval stage, viviparous, diaphragm between thorax and abdomen, endothermic.
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