Cartilagenous fish are grouped under____________.

Explanation

**Step-by-Step Solution:**

1. **Understanding Cartilaginous Fish**: Cartilaginous fish are a type of fish whose skeletons are made of cartilage rather than bone. This is a key characteristic that differentiates them from other types of fish.

2. **Classification**: Cartilaginous fish belong to a specific class within the animal kingdom. They are classified under the class known as "Chondrichthyes."

3. **Characteristics of Chondrichthyes**:
- They do not have a swim bladder, which is an organ that helps some fish maintain buoyancy.
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