Endoskeleton is cartilaginous in

Options

A. Elasmobranchs
B. Dipnoi
C. Mollusca
D. Osteichthyes

Answer

To determine which organism has a cartilaginous endoskeleton, we can follow these steps:

### Step 1: Understand the Types of Skeletons
- The endoskeleton can be either cartilaginous or bony. Cartilaginous skeletons are made of cartilage, while bony skeletons are made of bone.

### Step 2: Analyze the Options
- We have four options to consider:
1. **Elastomobrax**
2. **Dipnoid**
3. **Mollusca**
4. **Ostrich Thigh**

### Step 3: Evaluate Each Option
- **Option 1: Elastomobrax**
- This is a subclass of the class Chondrichthyes, which is known for having a cartilaginous endoskeleton. An example is the Scoliodon (shark).

- **Option 2: Dipnoid**
- Dipnoids are known as lungfishes and have a bony endoskeleton, making this option incorrect.

- **Option 3: Mollusca**
- Mollusca is a phylum of invertebrates and does not have an endoskeleton, so this option is also incorrect.

- **Option 4: Ostrich Thigh**
- This refers to a type of bony fish, which also has a bony endoskeleton, making this option incorrect as well.

### Step 4: Conclusion
- After evaluating all options, the only organism with a cartilaginous endoskeleton is **Elastomobrax**. Therefore, the correct answer is **Option 1**.

### Final Answer:
**Elastomobrax** has a cartilaginous endoskeleton.

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