Only the upper jaw has horny beak in

Options

A. Sphenodon
B. Alligator
C. Cobra
D. chelone

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which reptile has a horny beak only in the upper jaw. The options provided are Sphenodon, Alligator, Cobra, and Shallet.

2. **Identifying Key Features of Each Option**:
- **Sphenodon (Tuataras)**: Known to have a unique dental structure with a double row of teeth in the upper jaw and a single row in the lower jaw.
- **Alligator**: Has a more traditional set of teeth with no horny beak structure.
- **Cobra**: Possesses fangs and does not have a beak.
- **Shallet**: Not a commonly recognized reptile in this context.

3. **Analyzing Sphenodon’s Structure**:
- In Sphenodon, the upper jaw has a double row of teeth, while the lower jaw has a single row of teeth.
- When the mouth is closed, the single row of teeth in the lower jaw fits between the two rows in the upper jaw.

4. **Horny Beak Formation**:
- The upper jaw of Sphenodon is covered by a horny beak, which is a characteristic feature. This beak is formed due to the arrangement of the teeth and the structure of the jaw.

5. **Conclusion**: Based on the unique dental structure and the presence of a horny beak only in the upper jaw, the correct answer is Sphenodon.

**Final Answer**: The reptile that has a horny beak only in the upper jaw is **Sphenodon**.

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