Dicondylic skull is characteristic feature of
(a) Amphibia and mammalia
(b) Aves and mammalia
(c) Amphibia and reptilia
(d) Reptilia and aves

Options

A. Amphibia and mammalia
B. aves and mammalia
C. Amphibia and reptilia
D. Reptilia and aves.

Answer

To determine which group of animals has a dicondylic skull, we need to analyze the characteristics of the skull in the options provided.

### Step-by-Step Solution:

1. **Understanding Dicondylic Skull**:
- A dicondylic skull is defined by the presence of two occipital condyles. This structure allows for a greater range of head movement and is a key feature in certain vertebrates.

2. **Analyzing Each Option**:
- **Option (a) Amphibia and Mammalia**:
- Both amphibians and mammals possess a dicondylic skull. This means they have two occipital condyles, making this option a strong candidate.

- **Option (b) Aves and Mammalia**:
- While mammals have a dicondylic skull, birds (aves) generally have a monocondylic skull. Therefore, this option is incorrect.

- **Option (c) Amphibia and Reptilia**:
- Amphibians have a dicondylic skull, but reptiles typically have a monocondylic skull. Thus, this option is also incorrect.

- **Option (d) Reptilia and Aves**:
- Both reptiles and birds have a monocondylic skull, which makes this option incorrect as well.

3. **Conclusion**:
- After analyzing all the options, the only correct answer is **(a) Amphibia and Mammalia**, as both groups possess a dicondylic skull.

### Final Answer:
**(a) Amphibia and Mammalia**

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