These explain the evolution of Mammalia from Reptilia

Options

A. Seymouria
B. Prototherians
C. metatherians
D. Eutherians

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for an explanation of the evolution of Mammalia from Reptilia. This involves identifying a group or type of organism that serves as a link between reptiles and mammals.

2. **Identifying the Options**: The options provided are:
- A) Seymouria
- B) Prototherians
- C) Metatherians
- D) Eutherians

3. **Analyzing the Options**:
- **Seymouria**: This is a genus that is often considered a link between amphibians and reptiles, not specifically between reptiles and mammals.
- **Prototherians**: These are egg-laying mammals, which are indeed a significant evolutionary step. However, they are not extinct and are represented by modern monotremes like the platypus and echidna.
- **Metatherians**: This term refers to marsupials, which are not egg-laying mammals but give birth to underdeveloped young that continue to develop in a pouch. They are not the direct link between reptiles and mammals.
- **Eutherians**: These are placental mammals, which evolved later and are not the connecting link to reptiles.

4. **Connecting Link**: The egg-laying mammals (Monotremes) are considered the connecting link between reptiles and mammals due to their oviparous nature (laying eggs) which is similar to reptiles, while also possessing mammalian characteristics like hair and mammary glands.

5. **Conclusion**: Based on the analysis, the correct answer is **B) Prototherians**, as they represent the egg-laying mammals that bridge the evolutionary gap between reptiles and mammals.

**Final Answer**: B) Prototherians

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