Prototherians have evolved from

Options

A. Reptiles
B. Birds
C. Amphibians
D. Eutherians.

Answer

**Step-by-Step Solution:**

1. **Understanding Prototherians**: Prototherians are a subclass of mammals that are characterized by their egg-laying ability. They are also known as monotremes.

2. **Classification of Mammals**: Mammals are classified into two main subclasses: Prototheria and Theria. Prototherians are distinct because they share certain features with reptiles and birds.

3. **Evolutionary Background**: To determine the evolutionary origin of prototherians, we need to analyze their characteristics. Prototherians exhibit traits that are more aligned with reptiles than with birds or amphibians.

4. **Key Characteristics**:
- Prototherians lay eggs, similar to reptiles.
- Their skeletal structure and limb arrangement also show similarities to reptiles.
- Although they share the egg-laying trait with birds and amphibians, the majority of their other characteristics align more closely with reptiles.

5. **Elimination of Other Options**:
- **Birds**: While prototherians share the egg-laying trait, they do not share enough other characteristics to suggest a direct evolutionary lineage from birds.
- **Amphibians**: Similar to birds, amphibians also lay eggs, but the overall anatomical and physiological traits of prototherians are not aligned with amphibians.
- **Eutherians**: Eutherians are a separate subclass of mammals that give live birth and do not share the egg-laying characteristic of prototherians.

6. **Conclusion**: Based on the analysis of characteristics and evolutionary traits, it is concluded that prototherians have evolved from reptiles.

**Final Answer**: Prototherians have evolved from reptiles.

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