(1) Mammals possess mammary or milk glands to suckle the young ones.
(2) Mammals are warm-blooded animals with hairy covering on their body.
(3) Heart is four-chambered. There is only left aortic arch. The RBC are oval and nonnucleated.
(4) Skin has sweat and sebaceous glands.
(5) Limbs are of pentadactyle type with claws, hoofs, nails etc.
(6) The bones of the skull are united with wavy lines called sutures.
(7) There is an external ear called pinna and internal ear consists of three ossicles i.e., incus, stapes and malleus.
(8) The brain is well developed. 4
(9) Teeth are present in sockets (thecodont) and modified for carrying out different functions in different groups of animals.
(10) Mammals possess single bone (dentary) in their lower jaw.
(11) There is a muscular diaphragm separating the thorax and abdomen.
(12) Generally testes are present in the scrotal sacs. Male has a copulatory organ and female has clitoris.
(13) Viviparous except one group of mammal belonging to prototheria.
Parental care is observed. Gestation period is found i.e., time taken for the complete development of the embryo. Parental care is the utmost. Class Mammalia is divided into three sub classes. They are
Prototheria (Monotremata) Example: Platypus, Echidna.
Marsupialia (Metatherra) Example: Kangaroo,Koala Bear.
Eutheria (Plaeentals) Example: Rabbit Cow, Tiger, Cat, Bat, Rat
