Which of these is a living fossil?

Options

A. Labeo
B. Mystus
C. Tertradon
D. Latimeria

Answer

To determine which of the given options is a living fossil, we need to understand the concept of a living fossil and analyze the characteristics of the options provided.

### Step-by-Step Solution:

1. **Understanding Living Fossils**:
- A living fossil refers to a species that has remained relatively unchanged over a long period of geological time. These organisms exhibit primitive features that have been retained from their ancestors, showing little to no evolutionary change.

2. **Identifying Characteristics**:
- Living fossils typically have morphological features that are similar to those of ancient species. They provide a glimpse into the past and can often be traced back to periods such as the Triassic or earlier.

3. **Analyzing the Options**:
- In this case, the option provided is "Labio" (specifically referring to the genus which includes the species Labio rohita, commonly known as rohu fish).
- The morphology of Labio is noted to be similar to that of fishes from the Triassic period, which dates back approximately 230 million years ago.

4. **Conclusion**:
- Since Labio retains old traits and features that are identical to those of ancient fishes, it qualifies as a living fossil. Therefore, the correct answer to the question is Labio.

### Final Answer:
The living fossil among the options is **Labio**.

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