You may know that you are related to apes and monkeys. But did u know that you are

also related to bats, tigers, whales, kangaroos, and many more creatures?

“Mammals”

Presenters: Pema Khandu Phub Lhamo Tshering Lhamo

Describe different classes of mammal with examples

Kingdom Animalia---Phylum Chordata------Subphylum Vertebrata---------Class Mammalia

What is mammals?• Mammals are animals that have hair, are warm-

blooded, and nourish their young with milk.

General characteristics of mammals• Warm blooded animals.• Skin is more or less covered with hairs except Cetacea.• Sudoriporous (sweat) glands and sebaceous (oil) glands

are present in the skin.• Mammary glands in females to nourish the young ones.• External ear (pinnae) are present.

• Teeth are heterodont (differentiated into incisors, canines and molars), thecodont (embedded in the alveolar pockets of jaws) and diphyodont (only 2 sets of teeth, milk set replaced by permanent set).

• Skull with two occipital condyles which are formed entirely by exoccipitals.

• The lower jaw is composed of a single bone, on each side

• Vertebrae are gastrocentrous composed of three pieces, the centrum, and two epiphyses.

• With few exceptions mammal possess seven cervical vertebrae.

• The digits in the fore and hind limbs are never more than 5, but often reduced.

• Presence of muscular diaphragm between thoracic and abdominal cavities.

• Heart is four chambered with only one left aortic arch.

• RBC are non-nucleated.• Brain with four optic lobes.• Kidney is metanephros.• Penis is always present.• Viviparous (the young develops in the uterus for

some time and born alive).

Three classes of Mammals

1. Prototheria (Monotremes): are primitive egg-

laying mammals.

2. Metatheria (Marsupials/pouched mammal):

their young are born in an extremely immature

state.

3. Eutheria (Placental mammals): their young are

born at an advanced state.

Prototheria (Egg laying mammal)

Primitive mammalsConnecting link between the reptile and mammalGeneral characteristics Skeleton resembles that of reptile No external pinna present on the ear Teeth are present only in the young, adults with

horny beak A cloaca is present into which ureters and

urinogenitals sinus open Mammary glands are without nipples The pectoral girdle possesses large coracoid

bones and interclavicle

The pelvic girdle possesses epipubic bones extending from the pelvis

Vertebrate are without epiphyses The ribs have only a single head, the tuberculum being

absent In the skull , tympanic bulla and lacrimals are absent ; the

jugal is reduced or absent There is no corpus callosum in the brain The cochlea is a simple process of the sacculus and not

coiled Testes are abdominal Females are oviparous Found in Australia, Tasmania and New Guinea

Examples of prototheria

Echidna (spiny ant eater) Ornithorhynchus (Duck-billed

platypus)

Metatheria (pouched mammals)General characteristics• Young ones are born prematurely after very short

gestation• Marsupium or rood pouch is present in the

females• Mammary glands are sebaceous and bearing

nipples• Epipubic (marsupial) bones are usually present

and attached with the pubis• Separate coracoid and interclavicle are absent• Ribs bear two heads, tuberculum and capitulum

• Vertebrae with epiphyses• Corpus callosum is feebly developed or absent.• Vagina and uterus are double (didelphic condition)• Viviparous• Placenta is usually absent.ExamplesDidelphis (Opossum) Dasyurus (Tiger-cat)

Eutheria Placental mammalGeneral characteristics Give birth to young one Marsupium (marsupial pouch) is entirely absent. Mammary glands are well developed with

nipples. Epipubic bones are absent. Ribs bear two heads, tuberculum and capitulum. Clooca is absent. Corpus callosum is present Urinogenital organs open independently of the

rectum. Testes are usually contained in scortal sacs.

Warm blooded External pinna present Viviparous. The young always nourished for a

considerable time in the uterus by means of allantoicplacenta and born in a relatively advanced state.

Examples

• Insectivorous mammal- shrew,moles

• Aerial mammal – bat

• Aquatic mammal-whales

• Carnivorous mammal-tiger

• Hoofed mammal- horse

• Mammal with proboscis-elephant

• Primates-apes, monkeys

References

Verma, P.S. (1984). A manual of Practical Zoology:

Chordates. New Delhi: S. Chand & Company

Ltd.

Newman, H.H. (1981). The Phylum Chordata. Agra,

India : Satish Book Enterprise.

Thank you !