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 will analyze each statement provided in the question. Cyclostomata includes jawless fish like lampreys and hagfish.

1. **Statement Analysis**:
- **Statement 1**: "Living members of cyclostomata are parasites on true fishes."
- This statement is true. Many cyclostomes, particularly lampreys, are known to be parasitic on other fish.

- **Statement 2**: "The cranium is bony."
- This statement is false. The cranium of cyclostomata is cartilaginous, not bony.

- **Statement 3**: "Paired fins are absent."
- This statement is true. Cyclostomata do not have paired fins, which is a characteristic of this group.

- **Statement 4**: "They are cartilaginous."
- This statement is true. Cyclostomata have a cartilaginous structure.

2. **Conclusion**:
- The statement that is not true for cyclostomata is: "The cranium is bony."

### Final Answer:
The statement that is not true for cyclostomata is: "The cranium is bony."