Besides Annelida and Arthropoda, true metamerism is found in

Options

A. Ctenophora
B. Mollusca
C. Chordata
D. Porifera

Answer

To solve the question "Besides Annelida and Arthropoda, true metamerism is found in", we will analyze the options given and determine which phylum exhibits true metamerism.

### Step-by-Step Solution:

1. **Understanding Metamerism**:
- Metamerism refers to the segmentation of the body into repeated units or segments. True metamerism is characterized by segments that are similar both externally and internally. This is a key feature in certain animal phyla.

2. **Identifying the Given Phyla**:
- The question lists four options:
a. Ctenophora
b. Mollusca
c. Caudata
d. Porifera

3. **Analyzing Each Option**:
- **Ctenophora**: This phylum includes comb jellies, which do not exhibit true metamerism. They have a different body structure without segmentation.
- **Mollusca**: Mollusks, such as snails and clams, do not show true metamerism. They have a soft body, but it is not segmented in the same way as annelids or arthropods.
- **Caudata**: This class includes amphibians like salamanders. Caudata does exhibit true metamerism, as their bodies are segmented both internally and externally.
- **Porifera**: Sponges belong to this phylum and do not show any form of metamerism. They have a simple body structure without segmentation.

4. **Conclusion**:
- From the analysis, we find that the only phylum among the options that exhibits true metamerism, besides Annelida and Arthropoda, is **Caudata**.

### Final Answer:
- **Caudata**