Agnatha or Cyclostomata are characterised by

Options

A. Absence of jaws and presence of suctorial mouth
B. Presence of suctorial mouth, absence of jaws, presence of single nostril and unpaired fins
C. Absence of mouth, presence of single nostril
D. Round mouth with triradiate lips

Answer

**Step-by-Step Solution:**

1. **Understanding Agnatha/Cyclostomata**: Agnatha, also known as Cyclostomata, is a superclass of jawless fish. This group includes modern lampreys and hagfish, as well as some extinct species.

2. **Key Characteristics**:
- **Absence of Jaws**: One of the primary characteristics of Agnatha is that they do not have jaws, which distinguishes them from other vertebrates.
- **Presence of a Suctorial Mouth**: Instead of jaws, Agnatha have a round, suctorial mouth that is adapted for feeding.
- **Single Median Nostril**: Agnatha possess a single nostril located on the top of their head, which is a unique feature compared to jawed vertebrates.
- **Unpaired Fins**: These fish have unpaired fins, meaning they do not have paired pectoral or pelvic fins like other fish.

3. **Conclusion**: The defining characteristics of Agnatha or Cyclostomata include the absence of jaws, the presence of a suctorial mouth, a single nostril, and unpaired fins.

**Final Answer**: Agnatha or Cyclostomata are characterized by the absence of jaws, presence of a suctorial mouth, single median nostril, and unpaired fins.

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