The centrum of a vertebra which is concave on both sides is called
as

Options

A. Amphicoelous
B. Opisthocoelous
C. Acoelous
D. Procoelous

Answer

To solve the question regarding the type of vertebral centrum that is concave on both sides, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Terminology**:
- The term "centrum" refers to the central portion of a vertebra. It plays a crucial role in the structure and function of the vertebral column.

2. **Identifying the Types of Centra**:
- There are different types of centra based on the morphology of their anterior and posterior surfaces. The options provided are:
- Amphicillus
- Ophistocillus
- Acillus
- Procillus

3. **Analyzing Each Option**:
- **Amphicillus**: The prefix "amphi-" means both, and "cillus" refers to concavity. Thus, amphicillus indicates that both the anterior and posterior surfaces of the centrum are concave.
- **Ophistocillus**: This type has a concave posterior surface and a convex anterior surface.
- **Acillus**: The prefix "a-" means absent, indicating that there is no concavity on either side; both surfaces are flat.
- **Procillus**: This type has a concave anterior surface and a convex posterior surface.

4. **Conclusion**:
- Since the question specifically asks for a centrum that is concave on both sides, the correct answer is **Amphicillus**.

### Final Answer:
The centrum of a vertebra which is concave on both sides is called **Amphicillus**.

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