Which one of the following is not a living fossil?

Options

A. King crab
B. Sphenodon
C. Archaeopteryx
D. Peripatus

Answer

To determine which of the following options is not a living fossil, we need to first understand what a living fossil is and then analyze each option provided.

### Step-by-Step Solution:

1. **Definition of Living Fossil**:
- Living fossils are organisms that have remained relatively unchanged for millions of years and have survived through various environmental changes. They exhibit very little evolutionary change over time.

2. **Analyzing the Options**:
- **King Crabs**: King crabs are known to have existed for millions of years with little change in their morphology, making them a classic example of a living fossil.
- **Sphenodon**: Also known as tuatara, Sphenodon is another organism that has remained unchanged for a long period, dating back to the time of the dinosaurs. It is considered a living fossil.
- **Peripatus**: This is a genus of velvet worms that has existed for millions of years and shows very little evolutionary change, thus qualifying as a living fossil.
- **Archaeopteryx**: This organism is known as a transitional fossil that exhibits characteristics of both birds and reptiles. It is not a living fossil because it represents a significant evolutionary step and is not unchanged over time.

3. **Conclusion**:
- Based on the analysis, the organism that is not a living fossil is **Archaeopteryx**.

### Final Answer:
**Archaeopteryx** is not a living fossil.

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