During evolution in which of the following groups, pentadactyl limbs appeared first?

Options

A. Amphibians
B. reptiles
C. Birds
D. Mammals

Answer

To determine in which group pentadactyl limbs appeared first during evolution, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Pentadactyl Limbs**:
- Pentadactyl limbs are characterized by having five digits. This anatomical feature is significant in vertebrate evolution.

2. **Identifying the Groups**:
- The groups mentioned in the question are amphibians, reptiles, birds, and mammals.

3. **Examining Vertebrate Classification**:
- Vertebrates are classified into two superclasses: Pisces (fishes) and Tetrapoda (four-limbed animals).
- Fishes (Pisces) do not have limbs; instead, they possess fins.

4. **Analyzing Tetrapoda**:
- Tetrapoda includes amphibians, reptiles, birds, and mammals, all of which have limbs.
- Amphibians are the first group to evolve from fish and are characterized by having both hind limbs and forelimbs.

5. **Focusing on Amphibians**:
- Taking frogs as an example of amphibians, they possess both hind limbs and forelimbs.
- The hind limbs of frogs have five digits, which qualifies them as pentadactyl.

6. **Conclusion**:
- Since amphibians were the first group to exhibit pentadactyl limbs, the answer to the question is **amphibians**.

### Final Answer:
**Amphibians**