What is evolutionary significance of duck-billed platypus?

Explanation

### Step-by-Step Solution:

1. **Classification of Duck-Billed Platypus**:
- The duck-billed platypus is classified under the class of mammals.
- It specifically belongs to the subclass of prototherians, which is a group of egg-laying mammals.

2. **Characteristics of Duck-Billed Platypus**:
- The duck-billed platypus exhibits characteristics that are a mix of both mammals and reptiles.
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