Which among them is a living fossil?

Options

A. Hydrophis
B. Archaeopteryx
C. Sphenodon
D. Vipera

Answer

To determine which among the given options is a living fossil, we will analyze each option based on the definition of a living fossil. A living fossil is an organism that has remained essentially unchanged from earlier geological times and has few or no surviving close relatives.

### Step-by-Step Solution:

1. **Understand the term "living fossil":**
- Living fossils are organisms that have not changed significantly over millions of years and have very few or no close relatives alive today.

2. **Evaluate the options:**
- **Option 1: Hydrophis**
- Hydrophis is a genus of sea snakes. Sea snakes have several surviving relatives, which means they do not fit the definition of a living fossil.

- **Option 2: Archaeopteryx**
- Archaeopteryx is often referred to as a "missing link" between dinosaurs and birds. It is a fossil and does not exist in living form today, so it cannot be classified as a living fossil.

- **Option 3: Sphenodon**
- Sphenodon, also known as tuatara, is a reptile endemic to New Zealand. It is the sole surviving member of its order and has remained relatively unchanged for millions of years, making it a classic example of a living fossil.

- **Option 4: Vipera**
- Vipera is a genus of vipers. There are many surviving relatives of vipers, which disqualifies them from being considered living fossils.

3. **Conclusion:**
- Based on the analysis, the correct answer is **Sphenodon (Option 3)**, as it is a living fossil.