Heterocercal tall, placoid scales are found in one of the following

Options

A. Rohu
B. Neoceratodus
C. Scoliodon
D. Anguilla

Answer

To solve the question regarding which organism has a heterocercal tail and placoid scales, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Terms**:
- **Heterocercal Tail**: This refers to a tail structure where the upper lobe is larger than the lower lobe. This is commonly found in certain types of fish.
- **Placoid Scales**: These are small, tooth-like structures that cover the skin of some fish, particularly cartilaginous fish like sharks and rays. They provide protection and reduce drag while swimming.

2. **Identify the Options**:
- The options given are: Rohu, Neoceratodus, Scolidon, and Anguilla.

3. **Analyze Each Option**:
- **Rohu**: This is a type of freshwater fish (a carp) and does not have a heterocercal tail or placoid scales.
- **Neoceratodus**: This is a lungfish, which also does not have a heterocercal tail or placoid scales.
- **Scolidon**: This is a genus of sharks, which are cartilaginous fish. They possess a heterocercal tail and placoid scales.
- **Anguilla**: This refers to eels, which have a different tail structure and do not have placoid scales.

4. **Conclusion**:
- Based on the characteristics of each option, **Scolidon** is the only one that possesses both a heterocercal tail and placoid scales. Therefore, the correct answer is **Scolidon**.

### Final Answer:
Scolidon