Why Mammals Are So Unique?

Why Mammals are so unique?

In the following text, the question Why mammals are uniques? has been addressed. 

1. Few or many hairs on their bodies.
2. Skin having some modifications, bearing hairs, glands like sebaceous, sweat, and mammary.
3. The three smallest bones of the ear namely; the malleus, incus, and stapes, collectively the ossicles.
4. Two occipital condyles in their skull.
5. Seven vertebrae in their cervical region.
6. Presence of fuse pelvic bones.
7. They are diphyodont because they bear two sets of teeth, milk, and permanent teeth.
8. Eyelids are movable.
9. Pinna is the outer fleshy and visible part of the ear.
10. The presence of four limbs, modifies in some cases, performing many functions.
11. Four chambered hearts.
12. The red blood cells have no nucleus and are biconcave in appearance.
13. Voicebox is present and a secondary palate besides the primary palate.
14. The presence of a muscular diaphragm.
15. The kidneys are metanephros kidneys, the opening of ureters into the urinary bladder.
16. Highly developed brain, neocerebrum especially, and, presence of twelve pairs of cranial nerves.
17. They are endothermic and homeothermic status.
18. Mammals have separate sexes.
19. The fertilization is internal. Implantation of embryo happens into the uterus and there is the presence of the placenta.
20. Presence of fetal membranes known as amnion, chorion, and allantois.
21. The mother nourishes young ones with milk from their mammary glands until they are able to eat other foods.
22. The horns are made of keratin present on their heads.
23. The three horns namely; true horns, antlers, and rhinoceros horns.
24. The presence of four types of integumentary glands, sweat, sebaceous, scent, and mammary.

These all are the unique characters that clearly describe the class Mammalia.