Which one has the parietal eye?

Options

A. Coral snake
B. Garden lizard
C. Marine turtle
D. Sphenodon

Answer

**Step-by-Step Solution:**

1. **Understanding the Parietal Eye**: The parietal eye is a unique structure that evolves from an anterior evagination, specifically from the pineal organ. It is not a typical eye; instead, it is a separate outgrowth that develops from the roof of the diencephalon, which is a part of the brain.

2. **Identifying the Order with Parietal Eye**: The parietal eye is specifically found in the order Rhynchocephalia. This order is distinct from other reptilian orders, as members of Rhynchocephalia possess this unique eye structure.

3. **Analyzing the Given Options**:
- **Coral Snakes**: These belong to the order Squamata. Members of this order do not have parietal eyes; their eyes are attached to the skull.
- **Garden Lizard**: Also a member of the order Squamata, garden lizards similarly do not possess parietal eyes.
- **Marine Turtle**: This species falls under the order Testudines. Like the previous examples, marine turtles do not have parietal eyes; their eyes are attached to the skull cavity.
- **Sphenodon**: This organism belongs to the order Rhynchocephalia. It is known to have parietal eyes that grow from the roof of the diencephalon.

4. **Conclusion**: Based on the analysis, the correct answer to the question "Which one has the parietal eye?" is Sphenodon, as it is the only option that belongs to the order Rhynchocephalia, where parietal eyes are found.

**Final Answer**: Sphenodon

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