Which one of the following statement is not true for cyclostomata ?

Options

A. Living members of cyclostomata are parasite on true fishes.
B. Cranium is bony
C. Paired fins are absent
D. They lack jaw

Answer

To determine which statement is not true for cyclostomata, we can analyze the characteristics of this group step by step.

### Step-by-Step Solution:

1. **Understanding Cyclostomata**:
- Cyclostomata is a class of jawless fish that falls under the subphylum Vertebrata. They are characterized by their circular mouths and lack of jaws.

2. **Classification**:
- Cyclostomata is part of the superclass Agnatha, which includes jawless vertebrates. The two main groups within this classification are:
- **Agnatha**: Jawless vertebrates (includes cyclostomata).
- **Gnathostomata**: Jawed vertebrates.

3. **Characteristics of Cyclostomata**:
- Living members of cyclostomata, such as lampreys, are known to be parasitic on true fishes. They attach to the fish using their circular mouths.
- The cranium of cyclostomata is cartilaginous, not bony.
- Cyclostomata lacks paired fins, which is a characteristic feature of this group.
- They are indeed jawless, which is why they are classified under Agnatha.

4. **Evaluating the Statements**:
- **Option 1**: "Living members of the cyclostomata are parasites on true fishes." - This statement is true.
- **Option 2**: "Cranium is bony." - This statement is not true as the cranium is cartilaginous.
- **Option 3**: "Paired fins are absent." - This statement is true.
- **Option 4**: "They lack jaw." - This statement is true.

5. **Conclusion**:
- The statement that is not true for cyclostomata is **Option 2**, which claims that the cranium is bony.

### Final Answer:
**Option 2: Cranium is bony.**

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