1. Mammary Glands and Milk Production:
- While platypuses lack external nipples, they possess mammary glands and produce milk to nourish their young. This is a defining characteristic of mammals.
2. Fur:
- Platypuses are covered in a dense, waterproof fur, which is another hallmark of mammals.
3. Three Middle Ear Bones:
- Like all mammals, platypuses have three middle ear bones (malleus, incus, and stapes) which help transmit sound vibrations.
4. Endothermic Regulation:
- Platypuses are warm-blooded, maintaining a constant body temperature, another characteristic shared by mammals.
5. Give Birth to Live Young:
- Platypuses are viviparous, meaning they give birth to live young. While their young are underdeveloped, they are not hatched from eggs, which differentiates them from reptiles and birds.
6. Possession of a Diaphragm:
- Platypuses have a diaphragm, a muscle that aids in breathing, a feature common among mammals.
7. Four-Chambered Heart:
- They have a four-chambered heart, another shared feature of mammals.
8. Single Bone in the Lower Jaw:
- Like other mammals, platypuses have a single bone in their lower jaw, which is a unique characteristic.
9. Dental Structure:
- While adult platypuses lack teeth, their young possess temporary teeth. This is a feature common among mammals.
10. Hair Follicles:
- Platypuses possess hair follicles, which produce the fur that covers their bodies.
While the platypus exhibits some unique adaptations, like laying eggs and having a duck-like bill, these key features demonstrate its classification as a mammal.