Which one of the following in birds, indicated their reptilian ancestry

Options

A. Two special chambered crop and gizzard in their digestive tract
B. Eggs with a calcareous shell
C. Scales on their hind limbs
D. four chambered heart.

Answer

To answer the question "Which one of the following in birds indicates their reptilian ancestry?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Evolutionary Relationship**:
- Birds are believed to have evolved from reptiles. This means that certain characteristics may be shared between birds and their reptilian ancestors.

2. **Identifying Common Features**:
- We need to identify features that are common between birds and reptiles. Some of these features include:
- Presence of scales
- Type of eggs
- Heart structure

3. **Analyzing the Features**:
- **Scales on Hind Limbs**:
- Reptiles have scales covering their bodies, and birds have scales on their hind limbs (legs). This is a significant feature that indicates their common ancestry.
- **Egg Structure**:
- Reptiles lay eggs with leathery shells, while birds lay eggs with hard, calcareous shells. This difference suggests that the egg structure is not a direct indicator of their common ancestry.
- **Heart Structure**:
- Reptiles generally have a three-chambered heart (with the exception of crocodiles, which have a four-chambered heart), while all birds have a four-chambered heart. This feature is more of a divergence than a similarity.

4. **Conclusion**:
- The presence of scales on the hind limbs of birds is a characteristic that directly indicates their reptilian ancestry, as it is a feature retained from their ancestors.

### Final Answer:
The feature in birds that indicates their reptilian ancestry is the **scales on their hind limbs**.

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