Animals belonging to class Mammalia are referred to as mammals. Mammals are one of the most evolved species in the animal kingdom categorized under vertebrata.

They exhibit advanced characteristics which set them apart from all other animals. They are characterized by the presence of mammary glands through which they feed their younger ones.

They are distributed worldwide and have adapted well to their surroundings – from oceans, deserts and polar regions to rainforests and rivers etc.

Let us have a detailed look at the characteristics and classifications of the animals belonging to the class Mammalia.

Characteristics Of Mammals

Following are a list of distinct characteristics of mammals that separates them from other classes:

  1. Mammals are warm-blooded animals who give birth to their younger ones.

  2. They are the most dominant form of animals found in almost all types of habitats.

  3. They have mammary glands that help them produce milk to feed their younger ones

  4. Presence of region of the brain known as Neocortex

  5. Their skin possesses oil glands (sebaceous glands) and sweat glands (sudoriferous glands).

  6. The fur of hair throughout the body which helps animals adapt to their environment.

  7. They are heterodont, i.e., possess different types of teeth.

  8. Mammals also possess cervical vertebrae.

  9. The skull is dicondylic.

  10. The trunk is divided into thorax and abdomen.

  11. The mammals respire through lungs.

  12. Good sense of hearing as mammals are aided with 3 middle ear bones

  13. Mammals have a four-chambered heart. The sinus venous and renal portal system are absent.

  14. Presence of single-boned lower jaws.

  15. The brain is well developed divided into cerebrum, cerebellum and medulla.

  16. They possess 12 pairs of cranial nerves.

  17. Exhibit one of the most advanced forms of Diaphragms.

  18. The mammals can lay eggs also. They are known as viviparous.

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Classification Of Mammals

Mammalia has the largest class in the animal kingdom. Based on their reproduction, they are classified into three subclasses:

  • Eutheria

  • Metatheria

  • Prototheria


Mammals under this subclass give birth to young ones. The young ones are developed inside the mother and derive nutrition through the placenta from the mother. Furthermore, it consists of 19 orders, few of which are:

Order Examples
Proboscidea Elephants
Rodentia Rats
Artiodactyla Cows


Mammals belonging to this sub-class give birth to immature young ones, hence they stay in their mother’s pouch until they mature. For eg., Marsupials and Kangaroos. They are divided into seven different orders:




Marsupial modes






New world opossum






South American rat opossum


Also known as Monotremes, the sub-class Prototheria consists of egg-laying mammals. It has one order having 6 species

Order: Monotremata

Example: Duckbilled platypus, Echidna

General Classification of Mammals

The scientists have also classified the mammals on a general basis which makes it easy to learn about the mammals and their distinguishing characteristics.




Lion, Tiger, Dog


Kangaroo, Koala, Womba


Chimpanzee, Gorilla, Monkey


Squirrel. Mouse, Porcupine


Dolphins, Whales

Other mammals

Seal, Walrus, Sea-lion

For more information on Mammalia, its characteristics and classification, keep visiting BYJU’S website or download BYJU’S app for further reference.

Further Reading:

Frequently Asked Questions

What are the major characteristics of mammalia?

These are warm-blooded, hairy living organisms with mammary glands to feed their young ones.

Why is dolphin a mammal?

Dolphin is a mammal because it breathes through lungs and has mammary glands. Moreover, it does not lay eggs and gives birth to its young ones.

How are the mammals classified?

Mammals are classified as eutheria, prototheria, metatheria.

Give examples of prototherians.

Prototherians include platypus and echidna.

Quiz Of The Day!


  1. So good and clear notes and explanations. I like it.

  2. Thank you

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