What are peculiar about lung fishes?

Explanation

### Step-by-Step Solution:

1. **Definition of Lungfishes**: Lungfishes, scientifically known as Protopterus, are a unique group of fish that exhibit characteristics of both fish and amphibians.

2. **Connecting Link**: Lungfishes are considered a connecting link between two taxonomic groups: fish and amphibians. This means they possess features that are found in both groups, showcasing evolutionary transitions.

3. **Three-Chambered Heart**: One of the peculiar characteristics of lungfishes is their three-chambered heart. This is a trait commonly found in amphibians but not in typical fish, indicating their amphibian-like features.

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