Cyclostomes are characterised by the

Options

A. presence of scales
B. presence of jaws
C. absence of paired fins
D. absence of cranium

Answer

**Step-by-Step Solution:**

1. **Understanding Cyclostomes**: Cyclostomes are a group of jawless fish that include species like lampreys and hagfish. They are characterized by their unique anatomical features.

2. **Identifying Key Features**: Cyclostomes are known for having a suctorial mouth, which means they have a round mouth that is adapted for sucking. This indicates that they do not possess jaws.

3. **Body Structure**: The body of cyclostomes is typically round in shape, and they lack scales, which is a common feature in many other fish species.

4. **Presence of Cranium**: Cyclostomes do have a cranium, which is often referred to as a "brain box." This is important as it protects their brain and is a characteristic feature of vertebrates.

5. **Evaluating the Options**:
- **Presence of Skates**: Incorrect, as cyclostomes do not have skates.
- **Presence of Jaws**: Incorrect, as cyclostomes are defined by the absence of jaws.
- **Absence of Paired Fins**: Correct, cyclostomes do not have paired fins.
- **Absence of Cranium**: Incorrect, as cyclostomes do have a cranium.

6. **Conclusion**: Based on the evaluation of the options, the correct characteristic of cyclostomes is the "absence of paired fins."

**Final Answer**: Cyclostomes are characterized by the absence of paired fins.

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